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Mobile Phone Patent Abstract
The invention provides a piezoelectric oscillator that allows for
fine adjustment of the frequency after resin molding, a manufacturing
method therefor, and a mobile phone and an electronic apparatus
using the piezoelectric oscillator. The piezoelectric oscillator
can include a resonator package, in which a piezoelectric resonator
element is housed, and a semiconductor device, in which an oscillation
circuit that is electrically connected to the resonator package
is incorporated. The resonator package and the semiconductor device
can be fixed to corresponding different surfaces of an island portion
of a lead frame, and resin molding is performed so that a transparent
lid of the resonator package is exposed to the outside.
Mobile Phone Patent Claims
What is claimed is:
1. A piezoelectric oscillator, comprising: a resonator package
having a transparent lid, a piezoelectric container formed of a
plurality of insulating substrates, and a mounting terminal, in
which a piezoelectric resonator element is housed; and a semiconductor
device in which an oscillation circuit that is electrically coupled
to the resonator package is incorporated, the resonator package
and the semiconductor device being fixed to corresponding different
surfaces of an island portion of a lead frame, a terminal portion
of the semiconductor device being connected to the mounting terminal
of the resonator package by bonding wire, and resin molding being
performed such that a transparent lid of the resonator package is
exposed to an outside and each of the semiconductor device and resonator
package are contained within a same body of resin.
2. The piezoelectric oscillator according to claim 1, the lead
frame having the island portion and external terminal portions separated
from the island portion, at least a portion of the lead frame being
deformed such that a region of the island portion that is coupled
to at least the semiconductor device is positioned further away
from the transparent lid than the external terminal portions.
3. The piezoelectric oscillator according to claim 2, the island
portion having holding lead portions that have a smaller width than
the island portion and that extend outward, and the deformation
being provided at the holding lead portions.
4. The piezoelectric oscillator according to claim 3, portions
of the holding lead portions having deformation portions that facilitate
deformation.
5. The piezoelectric oscillator according to claim 4, the deformation
portions being defined by slits that penetrate the island portion
at opposite sides of the holding lead portions.
6. The piezoelectric oscillator according to claim 1, the resonator
package being fixed with at least three protrusion surfaces abutting
against the island portion, the protrusion surfaces slightly protruding.
7. A mobile phone apparatus using a piezoelectric resonator that
obtains a control clock signal, the piezoelectric resonator including
a resonator package having a transparent lid, a piezoelectric container
formed of a plurality of insulating substrates, and a mounting terminal
in which a piezoelectric resonator element is housed, and a semiconductor
device, in which an oscillation circuit that is electrically coupled
to the resonator package is incorporated, the resonator package
and the semiconductor device being fixed to corresponding different
surfaces of an island portion of a lead frame, a terminal portion
of the semiconductor device being connected to the mounting terminal
of the resonator package by bonding wire, and resin molding being
performed so that a transparent lid of the resonator package is
exposed to an outside and each of the semiconductor device and resonator
package are contained within a same body of resin.
8. An electronic apparatus using a piezoelectric resonator that
obtains a control clock signal, the piezoelectric resonator including
a resonator package having a transparent lid, a piezoelectric container
formed of a plurality of insulating substrates, and a mounting terminal
in which a piezoelectric resonator element is housed, and a semiconductor
device in which an oscillation circuit that is electrically coupled
to the resonator package is incorporated, the resonator package
and the semiconductor device being fixed to corresponding different
surfaces of an island portion of a lead frame, a terminal portion
of the semiconductor device being connected to the mounting terminal
of the resonator package by bonding wire, and resin molding being
performed so that a transparent lid of the resonator package is
exposed to an outside and each of the semiconductor device and resonator
package are contained within a same body of resin.
Mobile Phone Patent Description
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to a piezoelectric oscillator having a piezoelectric
resonator package housing a piezoelectric resonator element and
a semiconductor device including an oscillation circuit for oscillating
the piezoelectric resonator element, a manufacturing method for
the piezoelectric oscillator, and a mobile phone and an electronic
apparatus using the piezoelectric oscillator.
2. Description of Related Art
Piezoelectric oscillators have been widely used in packages for
HDDs (hard disk drives); mobile computers; or compact information
apparatuses, such as IC cards; and mobile communication apparatuses,
such as mobile phones, automobile phones, or paging systems. FIG.
22 shows an exemplary configuration of a conventional piezoelectric
oscillator (see, for example, "Micro Film" in Japanese
Unexamined Utility Model Registration Application Publication No.
1-82507). In the figure, the piezoelectric oscillator is configured
as follows. A semiconductor device 1 is fixed to one surface of
a lead frame 5 with an adhesive or the like and a piezoelectric
resonator 4 housed in a cylindrical package is fixed to the other
surface of the lead frame 5. The semiconductor device 1 and the
external terminals of the lead frame 5 are connected via bonding
wires 3. The entire structure is molded with a resin 6.
Such a structure can avoid various inconveniences when the piezoelectric
resonator element and the oscillation circuit are housed in the
same package. In other words, when the piezoelectric resonator element
and the oscillation circuit are simultaneously housed in the resin
package, a gas generated when the resin is cured may attach to the
piezoelectric resonator element, thus leading a decline in performance.
Accordingly, as described above, when the piezoelectric resonator
element and the oscillation circuit are housed in the separate packages
and are fixed to different surfaces of the lead frame, those inconveniences
can be avoided and the configuration can be miniaturized.
Such a configuration is also disclosed in another patent document
(see, for example, Japanese Unexamined Patent Application Publication
No. 7-162236).
SUMMARY OF THE INVENTION
However, with the conventional piezoelectric oscillators, when
a frequency displacement of the piezoelectric resonator becomes
problematic after resin molding, no measure therefor has been taken.
Specifically, in recent years, considerably high accuracy is required
for the frequency performance of a piezoelectric oscillator. After
the package of the piezoelectric resonator is sealed, when the frequency
of the piezoelectric resonator changes to a problematic extent due
to the influence of the subsequent manufacturing process or the
like, it is impossible to ship the piezoelectric oscillator as a
product. Further, the conventional piezoelectric oscillators have
some problems. Specifically, the components are wasted, the manufacturing
yield also decreases, and, consequently, the manufacturing cost
increases.
An object of the invention is to provide a piezoelectric oscillator
that allows for fine adjustment of the frequency after resin molding,
a manufacturing method therefor, and a mobile phone and an electronic
apparatus using the piezoelectric oscillator.
To achieve the foregoing object, a first aspect of the invention
provides a piezoelectric oscillator. The piezoelectric resonator
includes a resonator package, in which a piezoelectric resonator
element is housed, and a semiconductor device, in which an oscillation
circuit that is electrically connected to the resonator package
is incorporated. The resonator package and the semiconductor device
are fixed to corresponding different surfaces of an island portion
of a lead frame. Resin molding is performed such that a transparent
lid of the resonator package is exposed to the outside.
According to the configuration of the first aspect, resin molding
is performed such that the transparent lid of the resonator package
is exposed to the outside. Thus, even after assembly, the inside
of the resonator package can be illuminated with external laser
light for frequency adjustment through the transparent lid, which
makes it possible to adjust the frequency of the piezoelectric resonator
element in the resonator package. In other words, after the piezoelectric
resonator package is sealed, when the influence of the manufacturing
process or the like causes the frequency of the piezoelectric resonator
to be changed to a problematic extent, for example, the electrodes
of the piezoelectric resonator element can be partly vaporized with
the laser light, so that the frequency can be adjusted by a mass
reduction technique. Accordingly, the present invention can provide
a piezoelectric oscillator that can perform fine adjustment of the
frequency even after resin molding. Further, not only can the frequency
be adjusted but also unwanted wires and the like within the package
can be disconnected after products are manufactured.
According to a second aspect of the invention, in the configuration
of the first aspect, the lead frame has the island portion and external
terminal portions separated from the island portion. At least a
portion of the lead frame can be deformed such that a region of
the island portion, the region being connected to at least the semiconductor
device, is positioned further away from the transparent lid than
the external terminal portions.
According to the configuration of the second aspect, since at least
a portion of the lead frame is deformed such that the island portion
is positioned in a direction away from the transparent lid, the
transparent lid of the resonator package is pressed in the molding
dies in the direction in which the portion of the lead frame is
deformed. Thus, since the lid is pressed by the inner surface of
the molding die when molded so that they are in tight contact with
each other, the resin does not enter the outer surface side of the
lid, and thus no burr is generated between the inner surface of
the die and the lid. Accordingly, the entire surface of the transparent
lid can be appropriately exposed, without the need for removing
burrs from the surface of the lid after the manufacture.
According to a third aspect of the invention, in the configuration
of the second aspect, the island portion has holding lead portions
that have a smaller width than the island portion and that extend
outward, and the deformation is provided at the holding lead portions.
According to the configuration of the third aspect, since the holding
lead portions are formed to have a smaller width than the island
portion, stress generated during the resin molding is readily concentrated
at the holding lead portions. This allows the holding lead portions
to be appropriately deformed while avoiding the deformation of the
island portion associated with the fixing function of the lead frame
with respect to the resonator package and the semiconductor device.
Also, since stress generated from the deformation can be concentrated
at the holding lead portions, it is possible to prevent the semiconductor
device from being damaged.
According to a fourth aspect of the invention, in the configuration
of the third aspect, portions of the holding lead portions have
deformation portions for facilitating deformation. According to
the configuration of the fourth embodiment, when portions of the
holding lead portions further have deformation portions for facilitating
deformation, stress generated during the molding process can be
appropriately concentrated at the deformation portions. The deformation
portions can be provided by, for example, reducing the width of
appropriate positions of the holding lead portions relative to the
other regions.
According to a fifth aspect of the present invention, in the configuration
of the fourth aspect, the deformation portions are defined by slits
that penetrate the island portion at opposite sides of the holding
lead portions. According to the configuration of the fifth aspect,
since the deformation portions are defined by slits that penetrate
the island portion at opposite sides of the holding lead portions,
there is no need to reduce the width of the holding lead portions.
Further, it is possible to concentrate stress at the slit formation
regions while maintaining the component holding function during
the molding process, and is also possible to facilitate the deformation
of the deformation portions.
According to a sixth aspect of the present invention, in the configuration
of one of the first to fifth aspects, the resonator package is fixed
with at least three protrusion surfaces abutting against the island
portion. The protrusion surfaces slightly protrude. According to
the configuration of the sixth aspect, even when stress that causes
the lead frame to be partly deformed is applied to the resonator
package during the molding process, the resonator package can easily
be positioned horizontally with respect to the island portion, since
the resonator package abuts against the island portion at at least
three protrusion surfaces. This arrangement, therefore, can effectively
prevent the resonator package from being molded in a declined state.
A seventh aspect of the invention can provide a manufacturing method
for a piezoelectric oscillator. A lead frame is prepared which includes
a supporting frame that integrally supports a plurality of outer
ends of external terminal portions and outer ends of holding lead
portions that extend from an island portion serving as a die pad.
The method can include the steps of fixing a semiconductor device
incorporating an oscillation circuit to one surface of the island
portion, fixing a resonator package to another surface of the island
portion, providing necessary wires by wire bonding, and performing
resin molding on the semiconductor device and the resonator package
such that a transparent lid of the resonator package is exposed.
According to the configuration of the seventh aspect, when the
resin molding is performed while the semiconductor device and the
resonator package are fixed to the island portion, the transparent
lid of the resonator package can be exposed. With this arrangement,
even after the molding, the inside can be illuminated with external
laser light for frequency adjustment, through the transparent lid,
so that the frequency of a piezoelectric resonator element provided
in the resonator package can be adjusted. In other words, after
the piezoelectric resonator package is sealed, when the influence
of the manufacturing process or the like causes the frequency of
the piezoelectric resonator to be changed to a problematic extent,
for example, the electrodes of the piezoelectric resonator element
can be partly vaporized with the laser light, so that the frequency
can be adjusted by a mass reduction technique.
According to an eighth aspect of the invention, in the resin molding
step in the configuration of the seventh aspect, the transparent
lid is caused to abut against an inner surface of a first die for
molding the transparent lid and the first die and a second die are
combined with reference to the positions of the holding lead portions
such that at least a portion of the lead frame is deformed to cause
the transparent lid to be displaced inward in the dies. The first
die has a depth that is smaller than the thickness of the resonator
package.
According to the configuration of the eighth aspect, the depth
of the first die is made smaller than the thickness of the resonator
package. The transparent lid is arranged to abut against an inner
surface of the first die, the first die and the second die are combined
with reference to the positions of the holding lead portions, and
the resin molding is performed. By doing so, the resonator package
is displaced inward, i.e., toward the semiconductor device, so that
at least a portion of the lead frame is deformed. In this process,
the transparent lid of the resonator package is pressed in the molding
dies in the direction in which the portion of the lead frame is
deformed. Thus, since the lid is pressed by the inner surface of
the first die so that they are in tight contact with each other,
the resin does not enter the outer surface side of the lid and thus
no burr is generated between the inner surface of the die and the
lid. That is, the entire surface of the transparent lid can be appropriately
exposed, without the need for removing burrs from the surface of
the lid after the manufacture.
Furthermore, since stress generated during the resin molding process
is concentrated so that a portion of the lead frame is deformed,
it is possible to prevent the stress to be applied to the semiconductor
device and to prevent the semiconductor device being damaged.
According to a ninth aspect of the present invention, in the configuration
of one of the seventh and eighth aspects, after the resin molding
step, the inside of the resonator package is illuminated with laser
light for frequency adjustment through the transparent lid, which
is exposed to the outside, thereby adjusting the frequency of a
piezoelectric resonator element in the resonator package. According
to the configuration of the ninth aspect, after the resin molding
step, the inside of the resonator package is illuminated with laser
light for frequency adjustment through the transparent lid, which
is exposed to the outside, thereby adjusting the frequency of the
piezoelectric resonator element in the resonator package. With this
arrangement, after the final step in which head and pressure during
the manufacturing process are involved, the frequency of the resonator
element in the resonator package can be adjusted. In other words,
the frequency can be adjusted at a final stage before the shipment
of products. This arrangement, therefore, can eliminate defective
products that result from a frequency variation after the manufacture,
eliminate component wastes, and increase the manufacturing yield.
In a tenth aspect of the present invention, in the configuration
of one of the seventh to ninth aspects, in the wire bonding step,
resonator connection terminals of the semiconductor device and mounting
terminals of the resonator package are electrically connected by
the wire bonding, and other terminals of the semiconductor device
and inner leads of the external terminal portions of the lead frame
are electrically connected by the wire bonding. According to the
configuration of the tenth aspect, with regard to the electrical
connection between the resonator package and the semiconductor device,
they are not interconnected via the lead frame but are connected
by bonding wires. Thus, since they are coated by a molding resin
in the molding step, there is an advantage in that stray capacitance
between the terminals does not increase.
An eleventh aspect of the invention provides a mobile phone apparatus
using a piezoelectric resonator for obtaining a control clock signal.
The piezoelectric resonator includes a resonator package, in which
a piezoelectric resonator element is housed, and a semiconductor
device, in which an oscillation circuit that is electrically connected
to the resonator package is incorporated. The resonator package
and the semiconductor device are fixed to corresponding different
surfaces of an island portion of a lead frame, and resin molding
is performed so that a transparent lid of the resonator package
is exposed to the outside.
To achieve the foregoing object, a twelfth aspect of the invention
provides an electronic apparatus using a piezoelectric resonator
for obtaining a control clock signal. The piezoelectric resonator
can include a resonator package, in which a piezoelectric resonator
element is housed, and a semiconductor device, in which an oscillation
circuit that is electrically connected to the resonator package
is incorporated. The resonator package and the semiconductor device
can be fixed to corresponding different surfaces of an island portion
of a lead frame, and resin molding is performed so that a transparent
lid of the resonator package is exposed to the outside.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described with reference to the accompanying
drawings, wherein like numerals reference like elements, and wherein:
FIG. 1 is a schematic sectional view showing an embodiment of a
piezoelectric oscillator of the invention;
FIG. 2 is a schematic plan view of the piezoelectric oscillator
shown in FIG. 1;
FIG. 3 is a schematic plan view of a resonator package used for
the piezoelectric oscillator shown in FIG. 1;
FIG. 4 is a schematic sectional view taken along line B--B shown
in FIG. 3;
FIG. 5 is a schematic sectional view taken along line C--C shown
in FIG. 3;
FIG. 6 is a schematic cross sectional view of a structure in which
the piezoelectric oscillator shown in FIG. 1 is modified;
FIG. 7 is a flow chart showing a brief overview of an example of
a manufacturing process of the piezoelectric oscillator shown in
FIG. 1;
FIG. 8 is a schematic plan view showing one example of a lead frame
prepared in the manufacturing process shown in FIG. 7;
FIGS. 9(a) and 9(b) show a schematic view illustrating a part of
the manufacturing process shown in FIG. 7, FIG. 9(a) being a schematic
plan view and FIG. 9(b) being a schematic bottom view;
FIG. 10 is a schematic plan view illustrating a part of the manufacturing
process shown in FIG. 7;
FIG. 11 is a schematic plan view illustrating a part of the manufacturing
process shown in FIG. 7;
FIG. 12 is a schematic sectional view showing a state before the
dies are clamped in the process shown in FIG. 11;
FIG. 13 is a schematic plan view illustrating a part of the manufacturing
process shown in FIG. 7;
FIG. 14 is a schematic sectional view showing a state after the
dies are clamped in the process shown in FIG. 13;
FIG. 15 is a schematic plan view illustrating a part of the manufacturing
process shown in FIG. 7;
FIG. 16 is a schematic plan view illustrating the completed form
of the piezoelectric oscillator shown in FIG. 1;
FIG. 17 is a schematic sectional view illustrating a frequency
adjustment process in the manufacturing process shown in FIG. 7;
FIG. 18 is a schematic plan view illustrating a first modification
of the piezoelectric oscillator shown in FIG. 1;
FIG. 19 is a schematic sectional view illustrating a second modification
of the piezoelectric oscillator shown in FIG. 1;
FIG. 20 is a schematic cross sectional view showing a third modification
of the piezoelectric oscillator shown in FIG. 1;
FIG. 21 is a diagram showing a schematic configuration of a digital
mobile phone apparatus, which is one example of an electronic apparatus
using the piezoelectric oscillator according to the embodiment of
the invention; and
FIG. 22 is a schematic sectional view showing an example of a conventional
piezoelectric oscillator.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
FIGS. 1 and 2 show an embodiment of a piezoelectric oscillator
of the invention, FIG. 1 being a schematic sectional view thereof
and FIG. 2 being a schematic plan view thereof. FIGS. 1 and 2 show
the internal structure of a resin mold portion in a transparent
manner for convenience of understanding.
In the figures, a piezoelectric oscillator 70 has a resonator package
30, in which a piezoelectric resonator element is housed, and an
IC chip 80, which is a semiconductor device in which an oscillation
circuit that is electrically connected to the resonator package
30 is incorporated.
More specifically, the piezoelectric oscillator 70 can be constructed
as follows. The IC chip 80 is fixed to one surface (the upper surface
in FIG. 1) of a lead frame 10 and the resonator package 30 is fixed
to the other surface (the lower surface in FIG. 1) of the lead frame
10. The resulting structure is molded with a resin 21 such that
only a lid 39 of the resonator package 30 is exposed.
The resonator package 30 incorporated in the piezoelectric oscillator
70 of the embodiment will first be described with reference to FIGS.
3 to 5.
The resonator package 30 can be used singly as a piezoelectric
device, and in the embodiment, FIGS. 3 and 4 particularly show an
example in which the resonator package 30 is configured with a quartz
crystal resonator. The resonator package 30 has a housing container
(a ceramic container) 36 in which a piezoelectric resonator element
32 is housed. The housing container 36 is formed by depositing a
plurality of substrates, each being formed by shaping a ceramic
green sheet containing aluminum oxide as insulating material, and
then sintering the substrates. Each substrate has a predetermined
hole therein, so that, when stacked, the substrates have a predetermined
internal space S2 therein.
The internal space S2 can serve as a housing space for housing
the piezoelectric resonator element 32. In other words, as shown
in FIG. 4, in the embodiment, the housing container 36 is formed
by stacking a first multilayer substrate 61, a second multilayer
substrate 64, and a third multilayer substrate 68 from below. In
the figure, in the vicinities of left end portions in the internal
space S2 of the housing container 36, the second multilayer substrate
64 that is exposed to the internal space S2 and that defines the
internal bottom portion has electrode portions 31, which is formed
by, for example, plating a tungsten metallized member with nickel
and gold.
The electrode portions 31 provide external connections and supply
drive voltages. Conductive adhesives 43 are applied to the electrode
portions 31, a base 51 of the piezoelectric resonator element 32
is placed on the conductive adhesives 43, and the conductive adhesives
43 are cured. As the conductive adhesives 43, an adhesive that is
made by containing conductive particles, such as silver fine particles,
in a synthetic resin that serves as an adhesive component having
a bonding capability can be used. Alternatively, a silicone, epoxy,
polyimide conductive adhesive, or the like can be used.
The piezoelectric resonator element 32 can be formed by etching
a piezoelectric material, for example, quartz crystal. In this embodiment,
the piezoelectric resonator element 32 is formed to have a small
size and has a shape particularly shown in FIG. 3 to provide necessary
performance. In other words, the piezoelectric resonator element
32 has the base 51, which is fixed to the housing container 36 side,
and a pair of resonating arms 34 and 35, which bifurcate from the
base 51 and extend parallel to each other toward the right side
in the figure. Thus, a so-called turning-fork type resonator element,
which has the overall shape of a turning fork, is used for the piezoelectric
resonator element 32.
The resonating arms 34 and 35 of the piezoelectric resonator element
32 have corresponding elongated grooves 56 and 57, which have bottoms
and which extend in the longitudinal direction. As shown in FIG.
5, which is a cross-sectional view taken along line C--C shown in
FIG. 3, the grooves 56 and 57 are provided in both upper and lower
surfaces of the corresponding resonating arms 34 and 35.
Referring to FIG. 3, extraction electrodes 52 and 53 are provided
in the vicinities of two opposite ends in the lateral direction
at an end portion (the left end portion in FIG. 3) of the base 51
of the piezoelectric resonator element 32. Similarly, the extraction
electrodes 52 and 53 are formed on the reverse surface, not shown,
of the base 51 of the piezoelectric resonator element 32.
The extraction electrodes 52 and 53 are portions that are connected
to the electrode portions 31 adjacent to the housing container 36
shown in FIG. 3 with the conductive adhesives 43, as described above.
The electrode portions 31 adjacent to the housing container 36 are
connected to corresponding mounting terminals 31a provided on an
outer surface of the left end portion of the first multilayer substrate
61. In practice, the mounting terminals 31a can be provided at two
opposite ends in the lateral direction of the resonator package
30. Further, dummy electrodes 31b can be provided on an outer surface
of the right end portion of the first multilayer substrate 61. The
dummy electrodes 31b are not connected to the piezoelectric resonator
element 32, and have the same shape as the mounting terminals 31a.
The dummy electrodes 31b are provided at two opposite ends in the
lateral direction at the right end portion of the first multilayer
substrate 61.
The extraction electrodes 52 and 53 of the piezoelectric resonator
element 32 can be connected to corresponding excitation electrodes
54 and 55 (not shown) provided in the grooves 56 and 57 of the resonating
arms 34 and 35. As shown in FIG. 5, the excitation electrodes 54
and 55 are also formed at two opposite side surfaces of the corresponding
resonating arms 34 and 35. For example, with regard to the resonating
arm 34, the excitation electrodes 54 in the grooves 57 and the excitation
electrodes 55 on its side surface portions are adapted to have opposite
polarities to each other. With regard to the resonating arm 35,
the excitation electrodes 55 in the grooves 56 and the excitation
electrodes 54 on its side surface portions are adapted to have opposite
polarities to each other
As shown in FIG. 4, in the vicinity of substantially the center
of the bottom surface of the housing container 36, interconnected
through-holes 37a and 37b are formed in two multilayer substrates
61 and 64 included in the housing container 36, so that a through-hole
37 that is open to the outside is provided. Of the two through-holes
constituting the through-holes 37, the outer through-hole 37a, which
is a second hole located outside, has a larger inner diameter than
the first hole 37b, which opens to the inside of the resonator package
30. Thus, the through-hole 37 is shaped to have a stepped opening
with a downward step portion 62 in FIG. 4. A metal coating portion
is preferably provided on the surface of the step portion 62.
The through-hole 37 is filled with a metal sealant 38, which is
preferably selected from, for example, lead-free sealants, and is
selected from, for example, a silver brazing material, Au/Sn alloy,
and Au/Ge alloy. Correspondingly, the metal coating portion on the
surface of the step portion 62 is preferably formed by plating a
tungsten metallized member with nickel and gold.
The lid 39 is joined to the open upper end of the housing container
36 with a brazing material 36a, such as a low-melting-point glass,
to seal the housing container 36. The lid 39 is formed of a light
transparent material, particularly, thin-plate glass, so that metal
coating portions (described below) of the piezoelectric resonator
element 32 is illuminated with external laser light L2, as described
below, to allow the frequency to be changed by a mass reduction
technique.
A suitable material for making the lid 39 transparent is generally
glass. As such glass material, a thin-plate glass, e.g., borosilicate
glass, manufactured by down drawing is used.
With this structure, as shown in FIG. 4, the mounting terminals
31a, the dummy terminals 31b, and the metal sealant 38 provide protrusion
portions that slightly protrude at the bottom surface of the first
substrate 61 to such a degree corresponding to the thickness of
the electrodes. The amounts of protrusions of the mounting terminals
31a, the dummy terminals 31b, and the metal sealant 38 are substantially
equal.
Further, referring to FIG. 4, a depression 42 is provided by removing
a portion inside the second substrate 64. Consequently, in a case
in which the resonator package 30 is externally shocked, even when
the tips of the piezoelectric resonator element 32 are displaced
in the arrow D direction, the tips of the piezoelectric resonator
element 32 hit the inner bottom portion of the housing container
36, thereby effectively preventing the piezoelectric resonator element
32 from being damaged.
Constricted portions or notches 44 and 45, which are inwardly notched
at two opposite edges in the lateral direction, can preferably be
formed in the vicinities of base portions of the resonating arms
34 and 35 at the base 51 of the piezoelectric resonator element
32. This can effectively prevent the flexural vibrations of the
resonating arms 34 and 35 from leaking toward the base 51.
Next, referring to FIG. 1, the IC chip 80, which is a semiconductor
device, houses an oscillation circuit formed of an integrated circuit,
which is not shown. The IC chip 80 is fixed to one surface of an
island portion, described below, of the lead frame 10 by using,
for example, an epoxy or silicon adhesive 80a.
As shown in FIG. 2, one surface of the IC chip 80, the surface
being opposite to the surface joined to the lead frame 10, can be
provided with a plurality of terminal portions. These terminal portions
are connected to corresponding inner leads of external terminal
portions 11 (described below) of the lead frame 10 by wire bonding.
Naturally, the number of terminal portions of the IC chip 80 may
be larger or smaller than the number of terminal portions shown
in FIG. 2, depending on the type of the IC chip.
Referring to FIG. 2, the terminal portions 11 of the IC chip 80
in the embodiment are called, for example, gate/drain (G/D) terminals,
and serve as terminals for connection with the resonator package
30. The terminal portions 81 are connected using bonding wires 82
to the above-described mounting terminals 31a of the resonator package
30. Thus, with regard to the electrical connection between the resonator
package 30 and the IC chip 80, they are not interconnected via the
lead frame 10. This offers an advantage in that stray capacitance
does not increase between the terminals. Since individual configurations
of other terminal portions of the IC chip 80 are different from
each other depending on the type of the IC chip 80, the descriptions
thereof are omitted.
The piezoelectric oscillator 70 of the embodiment is configured
as described below, and is molded with the resin in a manufacturing
process described above such that the transparent lid 39 of the
resonator package 30 is exposed to the outside, as shown in FIG.
1. Thus, after assembly, the inside of the piezoelectric oscillator
70 can be illuminated with external laser light L2 for frequency
adjustment through the transparent lid 39, by the same method as
that described with reference to FIG. 4. As a result, after manufacture
of the piezoelectric oscillator 70, particularly, after resin molding,
the frequency of the piezoelectric resonator element 32 within the
resonator package 30 can be adjusted.
That is, after the lid 39 of the resonator package 30 is sealed,
when the influence of the manufacturing process, such as resin molding,
causes the frequency of the piezoelectric resonator element 32 to
be changed to a problematic extent, for example, the electrodes
of the piezoelectric resonator element 32 can be partly vaporized
with the laser light L2 by a mass reduction technique, so that the
frequency can be adjusted.
Additionally, not only can the frequency be adjusted, but also
unwanted wires and the like within the package can be disconnected
after products are manufactured.
In the above-described embodiment, the resonator package 30 can
be arranged at the lower side (the mounting substrate side) and
the IC chip 80 is arranged at the upper side so as to sandwich the
lead frame 10 therebetween. Alternatively, as shown in FIG. 6, the
arrangement may be such that the resonator package 30 is arranged
at the upper side and the IC chip 80 is arranged at the lower side
(the mounting substrate side) so as to sandwich the lead frame 10,
so that the lid 39 is exposed upward. In this case, the external
terminal portions 11 are formed to have a so-called J-lead shape
in which terminals 11a are bent downward (toward the mounting substrate)
so as to go around the resin 21.
FIG. 7 is a flow chart for a preferred embodiment of an exemplary
manufacturing method for the piezoelectric oscillator 70 of the
embodiment. FIG. 8 is a schematic plan view showing the configuration
of a lead frame prepared for the manufacture of the piezoelectric
oscillator 70.
Before describing a manufacturing method for the piezoelectric
oscillator 70, the structure of a lead frame will first be described
with reference to FIG. 8. Referring to FIG. 8, for the lead frame
10, one that is commonly used for manufacturing a package device
can be used. Examples include a lead frame formed of an Fe alloy,
such as a 42 alloy; a Cu metal, such as Cu--Sn, Cu--Fe, Cu--Zn,
or Cu--Ni; or ternary alloy containing a third element added to
those alloys.
The lead frame 10 has an outer frame portion 17, an island portion
12, and the external terminal portions 11. The island portion 12
is provided inside the outer frame portion 17 and in the vicinity
of substantially the center thereof to serve as a die pad. The external
terminal portions 11 are arranged to be parallel to each other at
two opposite sides of the island portion 12 in the lateral direction
to serve as lead portions. Further, the external terminal portions
11 are separated from the island portion 12 and are supported by
the outer frame portion 17. The number of external terminal portions
11 is determined so as to correspond to, for example, the number
of terminals of the IC chip 80 which are connected to the external
terminal portions 11.
The island portion 12 serves as a die pad for mounting a device
and has an area and a width which are suitable for the purpose.
The island portion 12 has holding lead portions 13 and 14 that integrally
extend from two opposite edges of the island portion 12. The holding
lead portions 13 and 14 have a width that is smaller than the width
of the island portion 12, extend toward the outer frame portion
17, and are integrated with the outer frame portion 17. Thus, the
island portion 12 has a structure in which it is supported with
respect to the outer frame portion 17 of the lead frame 10 by the
narrow holding lead portions 13 and 14.
Preferably, the island portion 12 is formed to have slits 15 and
slits 16, which are formed so as to penetrate the island portion
12 at two opposite sides in the lateral direction of the holding
lead portions 13 and 14, as shown in FIG. 8. That is, the slits
15 and the slits 16 are provided as one variation of a deformation
portion for facilitating the deformation of the holding lead portions
13 and 14 in a manufacturing process described below. Thus, instead
of the slits described above, the deformation portions may be notch
portions that are formed by notching a larger area of the island
portion 12. Alternatively, predetermined portions of the holding
lead portions 13 and 14 may be set to have a smaller width than
the other regions. In any case, the deformation portions can be
provided by forming structurally weak portions at the holding lead
portions 13 and 14 or the portion where the holding lead portions
13 and 14 and the island portion 12 are integrated with each other
so that stress generated in a molding process described below is
concentrated at that portion.
Alternatively, the island portion 12 may be provided with a deformation
portion by forming the island portion 12 such it has an irregular
shape itself, to allow a portion of the island portion 12 to be
deformed.
An embodiment of a manufacturing method for the piezoelectric oscillator
70 will now be described. As shown in step ST1 of FIG. 7, the IC
chip 80 is bonded as shown in FIG. 9(a) using the lead frame 10
illustrated in FIG. 8. In other words, one surface of the IC chip
80, the one surface being not the surface having the terminals of
the IC chip 80, is bonded to the island portion 12 of the lead frame
10 using the adhesive illustrated in FIG. 1.
FIG. 9(b) shows a surface opposite to the surface shown in FIG.
9(a). Next, as shown in FIG. 9(b), the resonator package 30 is bonded
to the island portion 12 using, for example, an epoxy or silicon
adhesive (step ST2). The adhesive is indicated by reference numeral
30a in FIG. 1. In this case, as shown in FIG. 9(a), the mounting
terminals 31a of the resonator package 30 are bonded and fixed so
as to be exposed from the island portion 12.
In this case, since the bottom surface of the resonator package
30 is bonded to the island portion 12, as illustrated in FIG. 4,
the dummy terminals 31b, which are arranged at two opposite end
portions in the lateral direction at the end portions in the lateral
direction of the resonator package 30, and the metal sealant 38,
which is provided in the vicinity of the center of the resonator
package 30, abut against the bottom surface of the resonator package
30 (see FIG. 9(b)).
Since the dummy terminals 31b and the metal sealant 38 provide
protrusion portions that slightly protrude to the same extent from
the bottom surface, the resonator package 30 abuts against the island
portion 12 at the three points. Thus, the resonator package 30 is
fixed without inclination relative to the island portion 12.
Next, as shown in FIG. 10, the individual terminals of the IC chip
80 and the corresponding inner leads of the external terminal portions
11 are connected by wire bonding (step ST3 in FIG. 7). In particular,
as illustrated in FIG. 2, the gate/drain (G/D) terminals, which
are the terminal portions 81 of the IC chip 80, are connected to
the above-described mounting terminals 31a, which are exposed from
the island portion 12 of the resonator package 30, by using the
bonding wires 82, such as gold (Au) lines. The bonding wires 82
are covered with a resin mold described below, so that the terminal
portions 81 of the IC chip 80 and their conductive portions are
not exposed to the outside. This can prevent moisture in the air
from attaching to those portions and thus can prevent short-circuiting.
As described above, electrical connections can be provided between
the lead frame 10 and the IC chip 80 and between the IC chip 80
and the resonator package 30.
Next, as shown in FIGS. 11 to 14, resin molding is performed (step
ST4 in FIG. 7).
For this molding, first and second molding dies 18 and 19 are used
as shown in FIGS. 11 and 12. The first die 18 is shown at the lower
side in FIGS. 12 and 14 and the second die 19 is shown at the upper
side in FIGS. 12 and 14.
In this process, the first die 18 and/or the second die 19 are
moved relative to each other in the arrow directions as shown in
FIG. 12, so that the periphery of the island portion 12 of the lead
frame 10 is sandwiched between the dies 18 and 19. The resonator
package 30 and the IC chip 80, which is fixed to the island portion
12, are housed in the dies and molten resin is injected into the
combined dies through a gate, which is not shown, so that a mold
is provided by transfer molding. In this case, for example, an epoxy
resin can be used for the molding resin.
In this case, as shown in FIG. 14, the first die 18 located below
is set to have a depth D that is smaller than a thickness h including
the lid 39 of the resonator package 30. As shown in FIG. 14, the
resonator package 30 and the IC chip 80, which is fixed to the island
portion 12, are housed between the first die 18 and the second die
19 and are sandwiched therebetween with reference to the positions
of the holding lead portions 13 and 14. That is, they are sandwiched
such that the seam of the first die 18 and the second die 19 are
set at the positions of the holding lead portions 13 and 14. The
resonator package 30 is arranged such that the lid 39 abuts against
an inner surface of the first die 18 in the dies. Furthermore, since
the depth D of the first die 18 is designed to be smaller than the
thickness h including the lid 39 of the resonator package 30, the
outer surface of the lid 39 is pressed strongly against the inner
surface of the first die 18 and the holding lead portions 13 and
14 are deformed as shown. That is, the holding lead portions 13
and 14 adjacent to the island portion 12 are deformed upward.
After the deformation, at least, a plane in which the external
terminal portions 11 that have the plurality of leads, which constitute
the external terminals, are located, and a plane in which the island
portion 12 exists are at different positions from each other.
In this case, stress generated during the above-described molding
work is not applied to the IC chip 80 but is concentrated at the
holding lead portions 13 and 14, thereby preventing the IC chip
80 from being damaged.
Furthermore, the resonator package 30 is deformed upward in the
figure, and the outer surface of the lid 39 is strongly pressed
against the inner surface of the first die 18. Thus, in this state,
molten resin is injected into the dies, so that the molten resin
surrounds the IC chip 80, which is fixed to the island portion 12,
and the resonator package 30, except for the outer surface of the
lid 39. As a result, this arrangement prevents the resin from entering
between the outer surface of the lid 39 and the inner surface of
the first die 18. This arrangement also prevents the resin from
becoming burrs and attaching to the outer surface of the lid 39
after the molding.
Next, in the state the dies are clamped, as shown in FIG. 13, connections
with the outer frame portion 17 are disconnected except for the
holding lead portions 13 and 14. That is, the outer edge portions
of the external terminal portions 11 are cut (step ST4 in FIG. 7).
Subsequently, portions exposed from the cut external terminal portions
11 are subjected to terminal plating (step ST5 in FIG. 7). As can
be seen from FIGS. 15 and 16, the outer edge portions of the external
terminal portions 11 are bent toward the lid 39 using a predetermined
jig to have the so-called J-lead shape (step ST6 in FIG. 7).
As shown in FIG. 17, after the formation of the piezoelectric oscillator
70, that is, after the resin molding, the electrode portions of
the piezoelectric resonator element 32 and so on are illuminated
with external laser light L2 through the transparent lid 39 that
is exposed to the outside. As a result, the metal coating portions
of the electrode portions and the like can be partly vaporized,
so that the frequency can be adjusted to be higher by a mass reduction
technique (step ST7 in FIG. 7). Thus, in any of the manufacturing
processes described above, for example, in the process involving
heat, such as the molding process, even when the frequency of the
resonator package 30 is changed, a final frequency adjustment can
be performed. Thus, it is possible to eliminate defective products
that result from such a frequency displacement. As a result, component
wastes can be eliminated and the manufacturing yield is increased.
Lastly, the structure is subjected to necessary inspection (step
ST8 in FIG. 7) to thereby provide the completed piezoelectric oscillator
70.
FIG. 18 is a schematic plan view showing a first modification of
the embodiment of the piezoelectric oscillation according to the
invention. Portions denoted with the same reference numerals as
those used in the description of the piezoelectric oscillator 70
have common structures, and thus the duplicated descriptions are
omitted. Now, differences will be mainly described. A piezoelectric
oscillator 70-1 of the first modification is different in the structure
of the island portion from the above-described piezoelectric oscillator
70.
That is, an island portion 12-1 does not have the slits 15 but
has a substantially rectangular plate shape. With this configuration,
similarly, in the molding process in step ST4 described above, stress
generated when the dies are clamped is concentrated at the holding
lead portions 13 and 14 that have a width smaller than the width
of the island portion 12-1. Thus, the holding lead portions 13 and
14 serve as deformation portions to prevent an event in which undue
stress applied to the IC chip 80 and so on causes damage.
Additionally, in the first modification, the shape of the island
portion 12-1 is simple, which facilitates the manufacture and also
improves the strength correspondingly.
FIGS. 19 and 20 show other modifications of the embodiment of the
piezoelectric oscillator of the invention. Specifically, FIG. 19
is a schematic sectional view in the lateral direction of a piezoelectric
oscillator 70-2 according to a second modification and FIG. 20 is
a schematic sectional view in the lateral direction of a piezoelectric
oscillator 70-3 according to a third embodiment. FIG. 20 illustrates
only the left side since the right and left sections thereof are
substantially symmetrical.
Hereinafter, since portions denoted with the same reference numerals
as those used in the descriptions of the piezoelectric oscillator
70 have common structures, differences will be mainly described
without redundant descriptions.
The piezoelectric oscillator 70-2 of the second modification and
the piezoelectric oscillator 70-3 of the third modification are
different from each other in the bending direction and the bending
form of the external terminal portions 11. In other words, as can
be seen from the comparison with FIG. 6 or 15, in the piezoelectric
oscillator 70-2 shown in FIG. 19, the vicinities of the base portions
of the external terminal portions 11 are bent in an opposite direction
to that in the piezoelectric oscillator 70, i.e., are bent toward
the IC chip 80, and tip portions 11b are bent in the horizontal
direction.
In the piezoelectric oscillator 70-3 shown in FIG. 20, the vicinities
of the base portions of the external terminal portions 11 are bent
toward the mounting substrate, not shown, (i.e., toward the lower
side in FIG. 20) and center portions vicinities 11c are bent in
the horizontal direction and are exposed to the outside. Further,
tip portions 11d of the external terminal portions 11 are bent toward
the resonator package 30 (i.e., toward the upper side in FIG. 20)
and are exposed to the outside so as to lie along side surfaces
of the resin 21.
As described above, while providing the same advantages as that
of the embodiment, the piezoelectric oscillators 70-2 and 70-3 of
the modifications of the invention can be configured to have different
forms of external terminals so as to correspond to, for example,
mounting conditions for the substrate.
FIG. 21 is a diagram showing a schematic configuration of a digital
mobile phone apparatus, which is one example of an electronic apparatus
using the piezoelectric oscillator according to the embodiment of
the invention.
In the figure, a sender's voice is converted by a microphone 308
into an electrical signal, which is then modulated by a demodulator/codec
unit into a digital signal. The digital signal is converted by a
transmitting unit 307 so as to have an RF (radio frequency) band
and the resulting RF signal is transmitted to a base station (not
shown) via an antenna. The frequency of an RF signal transmitted
from a base station is converted by a receiving unit 306. The resulting
signal is converted by the demodulator/codec unit into an audio
signal, which is then output from a speaker 309. A CPU (central
processing unit) 301 controls the entire operation of the digital
mobile phone apparatus 300, including an input/output section 302
constituted by a liquid crystal display device and a keyboard. A
memory 303 is information storing device, which is implemented by
RAM, ROM, and the like, and is controlled by the CPU 301. The memory
303 stores, for example, telephone-book information and a control
program for the digital mobile phone apparatus 300.
The piezoelectric oscillator according to the embodiment of the
invention can be applied to, for example, a TCXO (Temperature Compensated
X'tal Oscillator) 305. This TCXO 305 is a piezoelectric oscillator
having a small frequency fluctuation with respect to a change in
ambient temperature, and is widely applied to mobile phone apparatuses
as a frequency reference source for the receiving unit 306 and the
transmitting unit 307 shown in FIG. 21. In conjunction with recent
miniaturization of mobile phone apparatuses, demands for miniaturized
TCXOs are increasing. Thus, the TCXO 305 having the structure according
to the embodiment of the present invention is very useful for the
miniaturization.
In this manner, when the piezoelectric oscillator 70 according
to the above-described embodiment is used for an electronic apparatus,
such as the digital mobile phone apparatus 300, fine adjustment
of the frequency can be achieved even after the resin molding. This
arrangement, therefore, can improve the manufacturing yield and
can reduce the manufacturing cost. Thus, the arrangement can also
reduce the manufacturing cost of electronic apparatuses, such as
the digital mobile phone apparatus 300.
While this invention has been described in conjunction with the
specific embodiments thereof, it is evident that many alternatives,
modifications, and variations will be apparent to those skilled
in the art. Accordingly, preferred embodiments of the invention
as set forth herein are intended to be illustrative, not limiting.
There are changes that may be made without departing from the spirit
and scope of the invention. |