JP2003087072A - Manufacturing method of surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for manufacturing a surface acoustic wave device with high yield by decreasing distortion generated on a surface acoustic wave element and reducing the changes in the frequency characteristics, after sealing a package. SOLUTION: An adhesive layer is provided at the bottom face of a cavity of the package. A surface acoustic wave element of face-up is placed on the adhesive layer. The element is bonded by wire. The aperture of the package is sealed on a lid by welding, and the adhesive layer is thermally cured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a wire bond type surface acoustic wave device.

[0002]

2. Description of the Related Art FIG. 3 is a schematic sectional view showing the structure of a conventional wire bond type surface acoustic wave device disclosed in Japanese Patent Laid-Open No. 3-284006. In FIG. 3, 1 is a package housing, 2 is a surface acoustic wave element, 3 is an adhesive layer, 4 is an electrode pad provided on the surface acoustic wave element,
Reference numeral 5 is an electrode pad provided on the inner surface of the package, 6 is a gold wire, 7 is a lid, and 8 is a surface acoustic wave device. FIG. 4 is a process diagram for manufacturing the conventional wire bond type surface acoustic wave device shown in FIG.

As shown in FIG. 4, in the manufacture of a conventional surface acoustic wave device of the wire bond type, first, an adhesive is applied to the bottom surface of the cavity of the package housing 1 to form the adhesive layer 3 ( Step 1b). Next, the face-up surface acoustic wave element 2 is placed on the adhesive layer 3 (step 2).
b). Next, the adhesive layer 3 is heat-cured, and the surface acoustic wave element 2 is die-bonded (step 3b). Next, the electrode pad 4 provided on the surface acoustic wave element and the electrode pad 5 provided on the inner surface of the package are wire-bonded with the gold wire 6 (step 4b). Finally, the lid 7 plated with gold, nickel or the like is welded to a metallization (not shown) provided around the upper surface of the package housing 1 by a method such as welding to hermetically seal the package (step 5b). ).

[0004]

The surface acoustic wave element is a sensitive piezoelectric element made of tantalum lithium oxide or the like, and the frequency characteristic of the element changes with a slight distortion. Therefore, it is necessary to prevent the surface acoustic wave device from being distorted as much as possible.

However, in the above conventional manufacturing method, the lid 7
Since metal is used for the package housing 1 and ceramics is used for the package housing 1, when welding the lid 7 to the package housing 1, heat is concentrated on the lid 7 having high thermal conductivity, so that the temperature of the lid 7 is reduced. It is locally higher than the package housing 1. When the entire surface acoustic wave device 8 is air-cooled after welding, the thermally expanded lid 7 contracts to distort the package housing 1, and as shown in FIG. 5, an adhesive is applied to the bottom surface of the package housing 1. The surface acoustic wave element 2 fixed via the layer 3 is also distorted.

According to the stress simulation by the computer, the surface acoustic wave element 2 is distorted by about 0.05% due to the contraction of the lid 7 due to the temperature difference of about 500 ° C. during lid welding and cooling after welding. Occurs. The distortion of the surface acoustic wave element 2 causes a characteristic variation of about 3 MHz in terms of the band center frequency of the surface acoustic wave device.

Therefore, in the conventional manufacturing method, when an electrical characteristic test is performed after hermetically sealing, unlike the frequency characteristic when an electrical test is performed on a chip in a wafer state, most of them have a band center frequency of a surface acoustic wave device. It shifted to the high frequency side. That is, even if a chip in a wafer state is subjected to an electrical test to select a non-defective product, there is a problem that the frequency characteristic changes after hermetically sealing and the surface acoustic wave device becomes a defective product.

Even when the chips are selected by an electrical test in consideration of the variation amount of the band center frequency, the variation amount of the band center frequency can be determined by the die bond adhesive coating amount, coating shape, and welding time. Since the amount of heat input varies depending on the amount of heat input, the surface acoustic wave device does not always reach the required frequency range after hermetic sealing, and the surface acoustic wave device becomes a defective product.

That is, according to the present invention, the strain generated in the surface acoustic wave element 2 as described above is reduced, the change in the frequency characteristic after hermetically sealing is reduced, and the surface acoustic wave device is manufactured with a high yield. Aim to get a way.

[0010]

A first method of manufacturing a surface acoustic wave device according to the present invention comprises a step of providing an adhesive layer on the bottom surface of a cavity of a package having a cavity structure, and a face on the adhesive layer. A step of placing the surface acoustic wave element up, a step of wire-bonding the electrode pad provided on the surface acoustic wave element and an electrode pad provided on the inner surface of the package, and welding the open portion of the package. It is provided with a step of sealing with a lid and a step of thermally curing the adhesive layer after the step of sealing the package.

A second method of manufacturing a surface acoustic wave device according to the present invention comprises the step of providing an adhesive layer on the bottom surface of a cavity of a package having a cavity structure in the method of manufacturing the first surface acoustic wave device. Applying a liquid adhesive.

A third method of manufacturing a surface acoustic wave device according to the present invention, in the method of manufacturing a second surface acoustic wave device, preliminarily reacts an adhesive in an adhesive layer as a pre-step of a wire bonding step. Or a step of drying the adhesive layer.

A fourth method of manufacturing a surface acoustic wave device according to the present invention is the same as the method of manufacturing a second surface acoustic wave device, wherein an electrode is provided on the surface acoustic wave element with the adhesive layer cooled. Wire bonding between the pad and the electrode pad provided on the inner surface of the package.

A fifth method of manufacturing a surface acoustic wave device according to the present invention is characterized in that, in the method of manufacturing a first surface acoustic wave device, a step of providing an adhesive layer on a bottom surface of a cavity of a package having a cavity structure, It is to place a film adhesive.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. FIG. 1 is a process diagram for manufacturing the surface acoustic wave device of the first embodiment, and FIG. 2 is a schematic cross-sectional view of the surface acoustic wave device manufactured by the manufacturing method of the first embodiment. In FIG. 2, 1 is a package housing, 2 is a surface acoustic wave element, 3 is an adhesive layer,
4 is an electrode pad provided on the surface acoustic wave element, 5 is an electrode pad provided on the inner surface of the package, 6 is a gold wire,
Reference numeral 7 is a lid, and 8 is a surface acoustic wave device.

As shown in the process diagram of FIG. 1, first, a liquid adhesive is applied to the bottom surface of the cavity of the package housing 1 to form an adhesive layer 3 (step 1a). Next, the face-up surface acoustic wave element 2 is placed on the adhesive layer 3 and is adhesively fixed by the adhesive layer 3 (step 2a). Next, the electrode pad 4 provided on the surface acoustic wave element and the electrode pad 5 provided on the inner surface of the package housing are wire-bonded with the gold wire 6 (step 3a). Next, the lid 7 plated with gold, nickel or the like is welded, specifically, by seam welding,
The package is hermetically sealed by welding with a metallization (not shown) provided on the periphery of the upper surface of the package housing 1 (step 4).
a). Finally, the hermetically sealed package is heated at the curing temperature of the adhesive for a predetermined time to cure the adhesive layer 3 to bond the surface acoustic wave element 2 to the package housing 1. Also in the method of manufacturing the surface acoustic wave device of the present embodiment, the lid 7 is made of metal such as Kovar and the package housing 1 is made of ceramics such as alumina.
When seam welding is applied to the package casing 1, the locally heated lid 7 contracts when the lid 7 returns to room temperature after air cooling, causing the package casing 1 to be distorted. However, in the present embodiment, since the adhesive layer 3 is not cured, the adhesive layer 3 alleviates the distortion, and as shown in FIG. 2, the surface acoustic wave element 2 is hardly distorted. .

Therefore, in order to confirm that the surface acoustic wave device 8 manufactured in the present embodiment hardly causes distortion and is within the frequency characteristic range required as a good product,
For each of the wafer chip, the surface acoustic wave device after wire bonding (step 3a), and the surface acoustic wave device 8 after hermetically sealing the package and heating and curing the adhesive layer 3 (step 5a). The center frequency of the frequency band to be passed as a bandpass filter was measured. As a result, the center frequency of the element or device after each step hardly changes from the center frequency measured by the chip of the wafer, and is within the allowable range of the standard. Can be manufactured with a high yield.

The liquid adhesive used in the present embodiment may be any liquid adhesive as long as it can be applied to the bottom surface of the package housing 1. For example, a solventless adhesive obtained by mixing a liquid resin with a curing agent or a catalyst, or a solvent adhesive obtained by dissolving a solid resin in a solvent at room temperature and mixing a curing agent or a catalyst. However, from the viewpoint of mounting the surface acoustic wave element, the viscosity of the solventless liquid adhesive is preferably 10 to 1000 Pa · s. If the viscosity of the solventless liquid adhesive is less than 10 Pa · s, the adhesive strength of the adhesive is small and the element position may be displaced due to the force applied to the element during wire bonding. Since the temperature is raised, the viscosity further decreases, and the position of the surface acoustic wave element 2 may be displaced. Further, if the viscosity of the liquid adhesive is larger than 1000 Pa · s, it is difficult to apply the liquid adhesive to the bottom surface of the package housing, and the amount of expensive adhesive used increases, and the manufacturing cost of the surface acoustic wave device 8 increases. In addition, it is preferable that the liquid adhesive has thixotropy, because even if the liquid adhesive has a low viscosity, the surface acoustic wave element 2 is less likely to be displaced during wire bonding and heat curing of the liquid adhesive.

When the liquid adhesive used in the present embodiment is a solvent-type liquid adhesive in which a solid resin is dissolved in a solvent at room temperature, after the adhesive is applied to the bottom surface of the package housing 1, first, The solvent is volatilized and the adhesive layer 3 is made into a solid having tackiness. Next, the surface acoustic wave element 2 is placed on the adhesive layer 3, and the surface acoustic wave element 2 is adhesively fixed to the bottom surface of the package housing 1. Since the surface acoustic wave element 2 is adhesively fixed with a solidified adhesive having surface adhesiveness, displacement of the element due to the force applied to the element at the time of wire bonding is eliminated and ultrasonic energy required for wire bonding is eliminated. Is easily transmitted, and wire bonding can be reliably performed.
Also, when the adhesive layer 3 is heated to cure it, the adhesive layer 3 melts and becomes a liquid, but a high viscosity can be maintained, and the position of the surface acoustic wave element 2 hardly shifts during curing.

In this embodiment, the liquid adhesive can be applied by a dispenser method or a transfer method.
The method is not limited to these methods as long as it can be applied to the bottom surface of the package housing 1.

In contrast to the conventional method of heat-curing the adhesive before wire bonding, in the method of the present embodiment, the heat-curing of the adhesive is performed after wire bonding to the surface acoustic wave element 2, so that the gold wire Since 6 restrains the surface acoustic wave element 2, a liquid adhesive having a low viscosity and good workability is used, and even if the viscosity is further lowered by heating during curing, the surface acoustic wave element 2 is less likely to be displaced.

Embodiment 2. The manufacturing method of the surface acoustic wave device according to the present embodiment is the same as the manufacturing method according to the first embodiment immediately after the liquid adhesive is applied to the bottom surface of the cavity of the package housing 1, or on the adhesive layer 3. After the surface acoustic wave element 2 of the up position is placed and the adhesive layer 3 adheres and fixes it, it is heated at a temperature sufficiently lower than the curing temperature of the liquid adhesive. As the heating temperature, for example,
A temperature of 40 ° C. or more lower than the predetermined curing temperature of the liquid adhesive is used. Generally, the curing speed of the adhesive becomes about 1/2 when the curing temperature decreases by 10 ° C. Therefore, when the heating temperature of the adhesive is 40 ° C. or more lower than the predetermined curing temperature, the curing speed is 1/10 or less. The progress of the curing reaction of the adhesive due to this heating is slight. That is, the adhesive layer 3 is
Even if the above heat treatment is performed in the pre-process of wire bonding, if the package is hermetically sealed and heated to a predetermined curing temperature, it is liquefied and then cured. Is relaxed and then fixed to the package housing 1 by adhesion. That is, the surface acoustic wave element 2
Since almost no distortion occurs in the surface acoustic wave device 8, it is possible to prevent the frequency characteristics of the surface acoustic wave device 8 from changing.

The above heat treatment when a solventless liquid adhesive is used is a step of pre-reacting the adhesive layer 3. The heat treatment in this preliminary reaction step may be performed immediately after the liquid adhesive is applied to the bottom surface of the cavity or after the face-up surface acoustic wave element 2 is placed on the adhesive layer 3. Since the viscosity of the adhesive increases due to the heat treatment, it is possible to further prevent the displacement of the surface acoustic wave element 2 during wire bonding and curing of the adhesive layer. The heat treatment when using a solvent-type liquid adhesive is a step of drying the adhesive layer 3, and is performed immediately after the liquid adhesive is applied to the bottom surface of the cavity. The solvent is sufficiently volatilized by this heat treatment, that is, the drying of the adhesive layer 3, so that the solvent component is a comb-shaped electrode portion (not shown) of the surface acoustic wave element 2.
It is possible to prevent it from adhering to and changing its frequency characteristic.

Embodiment 3. The manufacturing method of the surface acoustic wave device according to the present embodiment is the same as the manufacturing method according to the first embodiment except that the adhesive layer 3 is cooled before the wire bonding of the surface acoustic wave element 2 and the adhesive layer 3 is cooled. Wire bonding in the state. Specifically, after the surface acoustic wave element 2 is placed on the adhesive layer 3 of the package and adhesively fixed, this package is cooled to about 5 ° C., for example, on a refrigerator or a cooling plate. The cooling temperature is not limited to 5 ° C as long as wire bonding can be normally performed. When the adhesive layer 3 is cooled, the viscosity is increased, the fixing force of the element is increased, the displacement of the surface acoustic wave element 2 due to the wire bond can be prevented, and the ultrasonic energy required for the wire bond is transmitted. It will be easier and wire bond can be surely done.

Fourth Embodiment The method for manufacturing the surface acoustic wave device according to the present embodiment is the same as the method for manufacturing the surface acoustic wave device according to the first embodiment, except that the step of providing the adhesive layer 3 on the bottom surface of the cavity of the package housing 1 is replaced with application of a liquid adhesive. That is, a film adhesive having tackiness is placed. In the present embodiment, since the adhesive is in the form of a film, a heating treatment or a cooling treatment of the adhesive layer 3 which is performed in the liquid adhesive in order to reduce the possibility of the displacement of the element during wire bonding is performed. It is unnecessary, and the number of manufacturing steps of the surface acoustic wave device 8 is small, and the productivity is improved. In addition, since the adhesive layer 3 can be obtained from a film having a uniform thickness by a punching method and the area and thickness of the adhesive layer 3 can be made uniform,
It is possible to avoid the problem that the coating thickness and the coating shape greatly vary and the frequency characteristics of the surface acoustic wave device 8 change.

Also in this embodiment, since the adhesive layer 3 is cured after the package is hermetically sealed, the adhesive layer 3 is liquefied and the distortion of the surface acoustic wave element 2 is relaxed. Therefore, the surface acoustic wave element 2 bonded and fixed is hardly distorted, and the frequency characteristics of the surface acoustic wave device 8 can be prevented from changing.

[0027]

EXAMPLES The present invention will be described in more detail by way of examples.

Example 1. An epoxy solvent-free liquid adhesive is applied to the bottom of the alumina package housing 1 by a dispenser to form an adhesive layer 3. Next, on the wafer chip, a network analyzer (MS462
3: Band center frequency measured by Anritsu) is 8
The 95 MHz surface acoustic wave element 2 is placed on the adhesive layer 3 and fixed by adhesion. Next, after wire-bonding the surface acoustic wave element 2, the Kovar lid 7 is attached to the open portion of the package housing 1.
Seam weld and hermetically seal the package. Next, the hermetically sealed package is subjected to heat treatment at the curing temperature and curing time of the adhesive (for example, 3 hours at 130 ° C.),
The adhesive layer 3 is cured. 100 produced in this way
With respect to the individual surface acoustic wave devices 8, there is no positional deviation of the elements during wire bonding, and the network analyzer (M
(S4623: manufactured by Anritsu Corporation), the frequency characteristics are measured, and the change range of the band center frequency is ± 1.5 MHz which is the standard.
As a result of obtaining the yield, the product in z was regarded as an acceptable product, and the yield rate was a high value of 85%.

Example 2. An epoxy solvent type liquid adhesive is used as the liquid adhesive, and the adhesive is applied to the bottom of the package housing 1 with a dispenser to form the adhesive layer 3, and then the adhesive layer 3 is air-dried. Other than the above, the surface acoustic wave device 8 is manufactured in the same manner as in Example 1. With respect to the 100 surface acoustic wave devices 8 thus manufactured, the yield was obtained in the same manner as in Example 1,
The non-defective rate was as high as 87%.

Example 3. The epoxy solventless adhesive used in Example 1 is applied to the bottom of the package housing 1 with a dispenser to form the adhesive layer 3, and then the adhesive layer 3 is heated to 80 ° C.
The surface acoustic wave device 8 is manufactured in the same manner as in Example 1 except that the heat treatment (preliminary reaction treatment) is performed for 15 minutes. The yield of the 100 surface acoustic wave devices 8 thus manufactured was determined in the same manner as in Example 1. As a result, the viscosity of the adhesive layer 3 increased due to a preliminary reaction. The non-defective product rate was improved to 92% by adding the effect of preventing defects due to the displacement of the element when the agent layer 3 was cured.

Example 4. The epoxy solvent-based adhesive used in Example 2 was dispensed on the bottom of the package housing 1.
Example 1 except that the adhesive layer 3 was heated at 80 ° C. for 15 minutes (drying treatment) after the coating was applied to form the adhesive layer 3.
The surface acoustic wave device 8 is manufactured in the same manner as. 100 surface acoustic wave devices 8 manufactured in this way
The yield was determined in the same manner as in Example 1, and as a result, the solvent of the adhesive layer 3 was sufficiently volatilized and the yield rate was 92.
% And improved.

Example 5. The surface acoustic wave element 2 is formed on the adhesive layer 3.
After mounting and adhesively fixing, the package bottom is brought into contact with a cooling plate equipped with a Peltier element, the adhesive layer 3 is cooled to 5 ° C., and the adhesive layer 3 is wire-bonded in a cooled state. The surface acoustic wave device 8 is manufactured in the same manner as in Example 1. With respect to the 100 surface acoustic wave devices 8 thus manufactured, the yield was obtained in the same manner as in Example 1. As a result, the viscosity of the adhesive layer 3 was increased and the defect due to the displacement of the element during wire bonding was caused. Can be prevented and the rate of non-defective products has improved to 91%.

Example 6. An epoxy-based film adhesive was used as the adhesive, and the adhesive layer 3 was formed by punching an adhesive strip formed from the film on the bottom of the package housing to form the adhesive layer 3. , The surface acoustic wave device 8 is manufactured. 10 produced in this way
The yield of 0 surface acoustic wave devices 8 was obtained in the same manner as in Example 1. As a result, since the adhesive layer 3 is a film, defects due to misalignment of elements during wire bonding or curing of the adhesive layer are prevented. At the same time, the influence of the solvent and the variation of the coating thickness and the coating shape of the adhesive layer were eliminated, and the non-defective rate was improved to 93%.

Comparative Example 1. Example 1 except that the adhesive layer 3 was formed using the epoxy solventless adhesive of Example 1 and the adhesive layer 3 was cured under the conditions shown in Example 1 before wire bonding. Similarly, the surface acoustic wave device 8 is manufactured. The yield of the 100 surface acoustic wave devices 8 thus manufactured was determined in the same manner as in Example 1. As a result, the surface acoustic wave element 2 was distorted due to the distortion of the package housing 1, and the surface acoustic wave devices were also distorted. In many cases, the band center frequency of 8 deviated from the standard, and the non-defective rate was 53.
% Was low.

[0035]

The first method of manufacturing a surface acoustic wave device according to the present invention comprises a step of providing an adhesive layer on the bottom surface of a cavity of a package having a cavity structure, and a face-up elastic surface on the adhesive layer. A wave element, a wire bond between an electrode pad provided on the surface acoustic wave element and an electrode pad provided on the inner surface of the package, and an opening of the package is sealed with a lid by welding. And the step of thermally curing the adhesive layer after the step of sealing the package, and in the step of sealing the surface acoustic wave device, the surface acoustic wave element is not distorted, so that the elastic surface The band center frequency of the wave device can be prevented from shifting, and the surface acoustic wave device can be manufactured with a high yield.

A second method of manufacturing a surface acoustic wave device according to the present invention is characterized in that, in the method of manufacturing a first surface acoustic wave device, a step of providing an adhesive layer on a bottom surface of a cavity of a package having a cavity structure, Applying a liquid adhesive, in addition to the effects of the first manufacturing method,
There is an effect that the adhesive layer can be easily provided.

A third method of manufacturing a surface acoustic wave device according to the present invention, in the method of manufacturing a second surface acoustic wave device, preliminarily reacts an adhesive agent of an adhesive layer as a pre-step of a wire bonding step. In addition to the effect of the second manufacturing method, it is possible to prevent the displacement of the surface acoustic wave element at the time of wire bonding or curing of the adhesive layer, or a step of drying the adhesive layer, or a solvent. This is effective in preventing element failure due to

A fourth method of manufacturing a surface acoustic wave device according to the present invention is the same as the method of manufacturing a second surface acoustic wave device, in which the electrode provided on the surface acoustic wave element with the adhesive layer cooled. Wire bonding between the pad and an electrode pad provided on the inner surface of the package.
In addition to the effect of the manufacturing method described above, there is an effect that the positional displacement of the surface acoustic wave element at the time of wire bonding can be prevented.

A fifth method of manufacturing a surface acoustic wave device according to the present invention comprises the step of providing an adhesive layer on the bottom surface of a cavity of a package having a cavity structure in the method of manufacturing the first surface acoustic wave device. The film-like adhesive is placed, and in addition to the effect of the first manufacturing method, it is possible to prevent the displacement of the surface acoustic wave element at the time of wire bonding or curing of the adhesive layer, and This has the effect of preventing changes in frequency characteristics due to variations in thickness and the effect of improving the productivity of surface acoustic wave devices.

[Brief description of drawings]

FIG. 1 is a process diagram for manufacturing a surface acoustic wave device according to a first embodiment.

FIG. 2 is a schematic sectional view of a surface acoustic wave device manufactured by the manufacturing method according to the first embodiment.

FIG. 3 is a schematic cross-sectional view showing the structure of a conventional wire bond type surface acoustic wave device disclosed in Japanese Patent Laid-Open No. 3-284006.

FIG. 4 is a process drawing for manufacturing a conventional surface acoustic wave device of a wire bond type.

FIG. 5 is a schematic view showing that a surface acoustic wave element is distorted in a conventional wire bond type surface acoustic wave device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 package housing, 2 surface acoustic wave elements, 3 adhesive layer, 4 electrode pads provided on the surface acoustic wave elements, 5
Electrode pads provided on the inner surface of the package, 6 gold wire, 7 lid, 8 surface acoustic wave device.

Claims (5)

[Claims] 1. A step of providing an adhesive layer on a bottom surface of a cavity of a package having a cavity structure, a step of placing a face-up surface acoustic wave element on the adhesive layer, and a step of providing the surface acoustic wave element. Wire bonding the formed electrode pad and the electrode pad provided on the inner surface of the package, sealing the opening of the package with a lid by welding, and heating the adhesive layer after the step of sealing the package. And a step of curing the surface acoustic wave device. 2. The method of manufacturing a surface acoustic wave device according to claim 1, wherein the step of providing the adhesive layer on the bottom surface of the cavity of the package having the cavity structure is applying a liquid adhesive. Method. 3. As a pre-process of the wire-bonding process,
The method for manufacturing a surface acoustic wave device according to claim 2, further comprising a step of pre-reacting the adhesive of the adhesive layer or a step of drying the adhesive layer. 4. The electrode pad provided on the surface acoustic wave element and the electrode pad provided on the inner surface of the package are wire-bonded to each other with the adhesive layer being cooled. Method of manufacturing surface acoustic wave device. 5. The surface acoustic wave device according to claim 1, wherein the step of providing the adhesive layer on the bottom surface of the cavity of the package having the cavity structure is placing a film adhesive. Manufacturing method.