JP4625287B2 - Sealing resin composition for electronic parts - Google Patents

Description

The present invention relates to a sealing resin composition that covers the periphery of an electronic component by screen printing, and more particularly relates to a sealing resin composition for an electronic component that covers the periphery of an electronic component that vibrates as a vibration source or changes its outer shape. .

  As an electronic component, for example, a vibration component mounted on a substrate as a vibration source of a touch panel has electrodes exposed on its surface, and is subject to secular change such as oxidation and sulfurization. Also, between electrodes and other conductors Therefore, the entire periphery is sealed with an insulating resin.

As a method of sealing an electronic component mounted on a substrate with a resin, a method of attaching a sealing resin composition to the periphery of the electronic component by screen printing is known. In this resin sealing method by screen printing, an insulating sealing resin composition is applied to the periphery of an electronic component in the form of screen printing ink. As shown in FIG. A metal mask plate 103 having a through hole 105 slightly larger and deeper than the contour of 120 covers the substrate 102 on which the electronic component 120 is mounted, and the squeegee 104 is slid along the surface of the metal mask plate 103. The sealing resin composition 106 is filled into the gap between the through hole 105 and the electronic component 120.

  Thereafter, as shown in FIG. 9, the metal mask plate 103 is removed upward, and the sealing resin 106 adhering to the periphery of the electronic component 120 is heat-cured and fixed around the electronic component 120 for sealing. .

As described above, the sealing resin composition that covers the periphery of the electronic component by screen printing has various properties such as viscosity suitable for screen printing ink, thermosetting property, insulation to prevent conduction between electrodes, and the like. Properties are required, and conventionally, a composition in which a filler is blended with an epoxy resin so as to satisfy this requirement is known (see Patent Document 1).

Japanese Patent No. 2824569 (2nd page, 4th column, 12th line to 18th line, 4th column, 49th line to 5th column, 5th line)

The filler compounded in the epoxy resin is used as an ink for screen printing, that is, an admixture that adjusts the properties of the sealing resin composition. In the conventional example described in Patent Document 1, thermal expansion of electronic components and substrates is performed. An inorganic filler such as silica is blended for the purpose of reducing the thermal expansion coefficient of the sealing resin composition so as to approach the coefficient.

However, when the blending amount of the inorganic filler is increased for the purpose of reducing the thermal expansion coefficient, the viscosity of the sealing resin composition is also increased, which is not suitable for screen printing requiring fluidity as an ink.

  In addition, even after adhering to the periphery of the electronic component 120, because the viscosity is high, it is pulled by the metal mask plate 103 to be removed upward, and becomes thick along the upper side of the electronic component 120. As shown in FIG. 9, it appears as an angular protrusion 106a. The rectangular protrusion 106a not only impairs the appearance of the electronic component 120 but also has an unplanned height, and thus interferes with other components and the substrate disposed on the electronic component 120, thereby reducing the size and bottom of the electronic component 120. It was a hindrance.

Furthermore, it is known that when the amount of the inorganic filler is increased, the bulk modulus increases. When the electronic component is the vibration component 120 mounted on the substrate, the sealing resin composition is used as the vibration component. This restrains the vibration of 120 and impairs the action as a vibration component.

The present invention has been made in view of such conventional problems, and provides a sealing resin composition for electronic components that reduces the coefficient of thermal expansion and does not increase the viscosity or volume modulus. The purpose is to do.

To achieve the above object, an electronic component sealing resin composition according to claim 1 is a solid wear on the touch panel of the touch panel input device, ambient piezoelectric substrate vibrates when the touch panel input device detects an input operation to be attached as an ink screen printing, a piezoelectric base plate by being heated curing an electronic component sealing resin composition for resin sealing an electronic component sealing resin composition, sealing the epoxy resin agent (a), a silicone resin filler is an organic filler (B), the entire molten silica filler is an inorganic filler (C) is 100 wt%, the epoxy resin encapsulant (a), 10 wt % Or 20% by weight of a silicon resin filler (B) and 40% by weight of a fused silica filler (C).

When the blending amount of the fused silica filler, which is an inorganic filler blended in the epoxy resin sealant , is decreased, the thermal expansion coefficient of the thermal expansion coefficient of the sealing resin composition increases, and the thermal expansion coefficient of the electronic component Since the difference is large, the electronic component is peeled from the substrate or the conductive pattern on the substrate connected to the electronic component is disconnected in an environment with a large temperature change.

(A) (B) By adding 40% by weight of fused silica filler to the whole of (C), the thermal expansion coefficient of the sealing resin composition is reduced, and the electronic component and the substrate on which the electronic component is mounted The difference with the coefficient of thermal expansion of the is reduced. Further, the shape of the sealing resin composition is increased and the shape adhering to the periphery of the electronic component is maintained until the resin is heated and cured, and the periphery of the electronic component is sealed with a uniform thickness. On the other hand, if the blending ratio of the fused silica filler is 40% by weight of the total, adding 10% by weight or 20% by weight of the silicon resin filler decreases the volume elastic modulus after thermosetting, and vibration of the piezoelectric substrate. Is not restrained.

If a silicone resin filler is not blended in the epoxy resin sealant, the volume modulus of elasticity after thermosetting is high and restrains the distortion of the piezoelectric substrate. Moreover, the viscosity before thermosetting is high, and it is pulled by the metal mask plate to be separated after screen printing, and square projections are generated.

By blending 10% by weight or 20% by weight of a silicone resin filler with respect to the whole of (A), (B), and (C) into the epoxy resin sealant, the volume elastic modulus after thermosetting decreases, Does not restrain the vibration of the piezoelectric substrate. In addition, the increase in viscosity due to the blending of the fused silica filler is suppressed, and no horn-shaped protrusions are generated after thermosetting.

The thermal expansion coefficient of the sealing resin composition decreases and the thermal expansion coefficient approaches the touch panel to which the piezoelectric substrate is fixed. Therefore, even in an environment where the temperature change is large, the touch panel The driving power supply pattern of the piezoelectric substrate wired on top does not break.

Since the increase in viscosity before thermosetting is suppressed, the sealing resin composition can be injected also into a narrow resin inflow space between the metal mask plate and the piezoelectric substrate. As a result, the periphery of the piezoelectric substrate can be covered with a thin sealing resin, and coupled with the decrease in the volume modulus of elasticity, the piezoelectric substrate can freely expand and contract without being constrained by the sealing resin composition. .

According to the first aspect of the present invention, the difference between the thermal expansion coefficient of the electronic component or the substrate and the thermal expansion coefficient of the sealing resin composition is reduced, and even in an environment where there is a temperature difference, the pattern wired on the substrate Will not break or crack in the encapsulating resin composition .

  In addition, it can be adjusted to an appropriate viscosity before thermosetting, so it is suitable for screen printing and maintains a uniform thickness without causing angular projections or conversely exposing the edges of electronic components. Can do.

In addition, when the encapsulating resin composition is heat-cured, the driving power supply pattern of the piezoelectric substrate does not break.

Further, since the periphery of the piezoelectric substrate can be covered with a thin sealing resin composition , even when the piezoelectric substrate is fixed in the vicinity of the operation area of the touch panel, the operation area is a part of the sealing resin composition. It is not covered with.

  Furthermore, since the distortion of the piezoelectric substrate itself is not constrained by the sealing resin, it is possible to generate the vibration of the touch panel that can be detected by the operator with a low driving voltage.

Hereinafter, a sealing resin composition for an electronic component (hereinafter referred to as a sealing resin composition 1) according to an embodiment of the present invention will be described with reference to FIGS. The sealing resin composition 1 according to the present embodiment is used as a sealing agent that seals the periphery of the piezoelectric substrate 2 provided in the touch panel input device 10 shown in FIGS. 1 and 2. The touch panel input device 10 and the piezoelectric substrate 2 which is an electronic component fixed to the touch panel 11 will be described with reference to FIGS. FIG. 1 is an exploded perspective view of the touch panel input device 10, and FIG. 2 is a rear view of the touch panel 11. In addition, all the weight% represented by the following embodiment is a weight ratio before hardening.

  The touch panel input device 10 is also called a digitizer. The touch panel 11 is configured by laminating a front side operation panel 11a and a back side support substrate 11b with a slight gap therebetween, and an operation area for detecting a pressed position inside the touch panel 11. 10A is set. The illustrated touch panel input device 10 detects a pressing position by a resistance pressure-sensitive method. For this purpose, conductor layers 12 and 13 made of a uniform resistance film are deposited on the opposing surfaces of the operation panel 11a and the support substrate 11b. The piezoelectric substrates 2 and 2 that are a pair of electronic components are fixed to the back side of the support substrate 11 b that is the touch panel 11.

  The operation panel 11a, the support substrate 11b, and the conductor layers 12 and 13 attached to the opposing surfaces of the operation panel 11a are arranged on the inside (back side of the touch panel input device 10) through the operation area 10A. Each is formed of a transparent material so that a pressing operation can be performed while viewing the display screen of the display device 14.

  The piezoelectric substrate 2 is formed in an elongated band shape, a pair of drive electrodes 2a and 2b is formed on both front and back surfaces, and the front side is the back side of the support substrate 11b that becomes a touch panel using an adhesive or the like. In order not to block the line of sight to the display device, it is fixed in a slight gap between the operation area 10A and the periphery of the support substrate 11b (see FIG. 2).

  The pressing operation to the operation area 10A is detected by contact between the conductor layers 12 and 13, and when the pressing operation is detected, a driving voltage is applied to the pair of driving electrodes 2a and 2b of the piezoelectric substrate 2 to expand and contract. The entire touch panel 11 including the support substrate 11b to which the piezoelectric substrate 2 is fixed is vibrated, and the operator confirms that the pressing operation has been accepted from the vibration.

Since the drive electrodes 2a and 2b of the piezoelectric substrate 2 fixed to the back surface of the support substrate 11b are exposed on the front, back, and side surfaces, the insulation from other components and the aging of the drive electrodes 2a and 2b itself are caused. In order to prevent deterioration, the entire periphery is sealed with an insulating sealing resin composition 1 using a screen printing method.

  The step of resin-sealing the periphery of the piezoelectric substrate 2 fixed to the touch panel 11 using the screen printing method is performed so as to cover the support substrate 11b with the fixed side of the piezoelectric substrate 2 as the front side as shown in FIG. Then, the metal mask plate 4 having the through holes 3 is overlapped on the corresponding portion of the piezoelectric substrate 2. In the overlapped state, a resin inflow space 5 is formed between the periphery of the piezoelectric substrate 2 and the inner wall surface of the through hole 3.

The interval between the resin inflow spaces 5 is equal to or less than the gap d (see FIG. 2) between the operation area 10A and the piezoelectric substrate 2 so that the sealing resin composition 1 attached to the side surface of the piezoelectric substrate 2 does not protrude toward the operation area 10A. Here, it is 0.5 mm which is equal to the distance d. The thickness of the metal mask plate 4, that is, the height of the through hole 3 is 1 mm, which is higher than the height of the piezoelectric substrate 2, assuming that the height is 0.7 mm.

The encapsulating resin composition 1 in the fluidized state, which becomes the ink for screen printing, is placed on one side of the metal mask plate 4 superimposed on the touch panel 11 in this way, and as shown in FIG. By sliding along the surface of the plate 4, the resin inflow space 5 is uniformly filled.

Thereafter, the metal mask plate 4 is pulled up in the vertical direction orthogonal to the support substrate 11b until the viscous sealing resin composition 1 is completely separated from the piezoelectric substrate 2 side. In the state shown in FIG. 4 in which the metal mask plate 4 is completely removed, the sealing resin composition 1 adheres to the entire circumference of the piezoelectric substrate 2 with a uniform thickness of approximately 0.5 mm.

The piezoelectric substrate 2 to which the sealing resin composition 1 is attached in this manner moves into the high-temperature furnace at about 180 ° C. together with the support substrate 11b, and the sealing resin composition 1 is thermally cured and fixed. The piezoelectric substrate 2 encapsulated with the thermosetting encapsulating resin composition 1 is not in contact with the outside air, prevents deterioration due to aging, and the electrodes are covered with the insulating encapsulating resin composition 1. There is no danger of short circuiting with others.

The sealing resin composition 1 attached to the periphery of the piezoelectric substrate 2 as the ink for screen printing described above must have at least insulating properties, thixotropic properties, and thermosetting properties. An epoxy resin having these characteristics is used, and a bisphenol type epoxy resin is used in this embodiment mode.

The insulation covers the entire surface of the piezoelectric substrate 2 from which the set of drive electrodes 2a and 2b is exposed. Therefore, in order not to short-circuit these electrodes, the thermosetting is heated after filling, and the piezoelectric substrate 2 is heated. In order to cure around, it is required as a characteristic of the sealing resin composition 1. The thixotropy is also called thixotropy or thixotropy, which means that the viscosity decreases during flow and returns to the original high viscosity state when left standing. 5 is required to increase the viscosity to the extent that the shape is maintained until it is heated and cured after filling.

In addition, the sealing resin composition 1 is required to have a low coefficient of thermal expansion and a low volume modulus after thermosetting. A low thermal expansion coefficient is required because the piezoelectric substrate 2 is a ceramic and the touch panel 11 is a glass substrate, each of which is made of a material lower than the thermal expansion coefficient of the sealing resin composition 1 that is a synthetic resin. If the thermal expansion coefficient of the resin 1 is high and the difference is large, cracks occur in the sealing resin composition 1 during the heat curing process or in a usage environment where the temperature change is large, or the wiring pattern on the touch panel 11 peels off. This is because there is a risk of disconnection. For example, when the sealing resin composition 1 is filled in the resin inflow space 5, a driving power supply pattern (see FIG. 5) is drawn from the driving electrodes 2 a and 2 b of the pair of piezoelectric substrates 2 and wired on the touch panel 11. 2c, 2d, 2e, and 2f), if the difference in the coefficient of thermal expansion from the touch panel 11 is large, the sealing resin composition 1 can be used in the environment of heat curing and a large temperature change. The driving power supply patterns 2c, 2d, 2e, and 2f are pulled in, and the patterns are peeled off and cut.

  Further, the reason why the low volume modulus after thermosetting is required is that the touch panel 11 is vibrated freely by the distortion without restraining the distortion of the piezoelectric substrate 2 as a vibration generation source after the curing.

In order to reduce the thermal expansion coefficient of the sealing resin composition 1 based on an epoxy resin, it is known to increase the blending amount of an inorganic filler such as silica. By blending the organic filler in an amount of not less than% by weight, a sealing resin composition 1 having a thermal expansion coefficient of 200 ppm / ° C. or less as an allowable limit and a volume modulus of elasticity of 3000 MP or less as an allowable limit was obtained.

Table 1 shows the thermal expansion coefficient (ppm / ppm ) of each sealing resin composition 1 for Examples 1 to 4 and Comparative Examples 1 and 2 in which the compounding ratios of the epoxy resin, the inorganic filler, and the organic filler were changed. ° C) and the bulk modulus (MPa). In these examples and comparative examples, the epoxy resin is a bisphenol-type epoxy resin, the inorganic filler is fused silica, the organic filler is a silicon resin, and the numerical values in the tables showing the respective amounts are weight ratios (% by weight). ).

As shown in Table 1, when the blending amount of the inorganic filler is increased, the thermal expansion coefficient decreases with the blending amount, but the volume elastic modulus also increases, and 50 wt% of the inorganic filler and no organic filler are blended. In the sealing resin composition 1 of Comparative Example 1, although the thermal expansion coefficient can be reduced to 127 ppm / ° C., the volume modulus becomes 4500 MPa exceeding the allowable limit of 3000 MPa, and the distortion of the piezoelectric substrate 2 to be sealed is reduced. As a result, the touch panel 11 cannot obtain a large vibration amplitude.

In Comparative Example 1, the viscosity of the encapsulating resin composition 1 in the fluidized state also increases, and is pulled by the metal mask plate 4 that is removed upward as shown in FIG. 6, along the upper side of the piezoelectric substrate 2. An angular protrusion 1a appears.

Furthermore, although it has thixotropy, the original viscosity is increased, so that the sealing resin composition 1 cannot be filled up to the inner bottom of the resin inflow space 5 of the narrow gap d, and the touch panel 11 side of the piezoelectric substrate 2 is not filled. There is a possibility that an unsealed opening may occur.

On the contrary, in the sealing resin composition 1 of Comparative Example 2 in which only 40% by weight of the organic filler is blended with 60% by weight of the epoxy resin, the volume modulus is sufficiently lowered to 1000 MPa, but the thermal expansion coefficient is within the allowable limit. Since it is as high as 252 ppm / ° C. exceeding 200 ppm / ° C., cracks are likely to occur in the encapsulating resin composition and damage to the drive power supply pattern is likely to occur. Moreover, as shown in FIG. 7, since the viscosity decreases, the shape of the sealing resin composition 1 attached to the piezoelectric substrate 2 before thermosetting cannot be maintained, and the shape is thin and leans downward. If it is attached, the edge portion of the piezoelectric substrate 2 is exposed.

In Example 1 in which 40% by weight of the epoxy resin and 40% by weight of the inorganic filler and 20% by weight of the organic filler were blended, the thermal expansion coefficient of the sealing resin composition 1 was 180 ppm / ° C., and the bulk modulus was 2500 MPa. Within limits. In addition, the viscosity becomes an appropriate viscosity and, as shown in FIG. 5, the entire circumference of the piezoelectric substrate 2 is completely covered while being thin without being leaned down along the side surface of the piezoelectric substrate 2 before being heated and cured. The shape is maintained in the state.

In Example 2, in which the epoxy resin was increased by 10% by weight and the organic filler was decreased by 10% by weight with respect to the blending ratio of Example 1, the thermal expansion coefficient of the sealing resin composition 1 decreased to 170 ppm / ° C. Also, the bulk modulus does not change substantially from Example 1, but the viscosity increases slightly.

In the encapsulating resin composition 1 of Example 3 in which the epoxy resin was further increased by 5% by weight and the inorganic filler was decreased by 5% by weight with respect to the blending ratio of Example 2, the thermal expansion coefficient corresponding to the reduced amount of the inorganic filler. Increases to 190 ppm / ° C., but the bulk modulus decreases to 2300 MPa and becomes elastic.

In Example 4, in which 25% by weight of the epoxy resin was blended with 25% by weight of the epoxy resin and 20% by weight of the organic filler, 15% by weight of the inorganic filler was reduced with respect to the blending ratio of Example 1, and the sealing resin composition Although the volume elastic modulus of the product 1 is lowered from 2500 MPa to 2000 MPa, since the organic filler is blended by 20% by weight, the coefficient of thermal expansion can be suppressed to 195 ppm / ° C. within an allowable limit.

In Example 5 in which 50% by weight of an inorganic filler and 20% by weight of an organic filler were blended with 30% by weight of an epoxy resin, 20% by weight of an organic filler was added to the blending ratio of Comparative Example 1, and an epoxy equivalent to the blended amount of the organic filler. Although the resin is reduced, the volume elastic modulus of the encapsulating resin composition 1 decreases from 4500 MPa to 2600 MPa, falls within an allowable limit that does not constrain the distortion of the piezoelectric substrate 2, and the viscosity also decreases. No protrusion 1a is generated. In Example 5, the coefficient of thermal expansion increases as compared with Comparative Example 1, but it is 175 ppm / ° C. within the allowable limit.

In the above-described embodiment, the piezoelectric substrate 2 fixed to the touch panel 11 is described as an electronic component to be resin-sealed. However, a sealing resin that seals an electronic component that operates after changing its outer shape after being mounted on the substrate. It can also be applied to compositions .

The present invention is suitable for a sealing resin composition for electronic components in which a sealing resin composition is attached to a periphery of a vibration component mounted on a substrate such as a printed wiring board using a screen printing method.

3 is an exploded perspective view of the touch panel input device 10. FIG. It is a rear view of the support substrate 11b to which the piezoelectric substrate 2 adheres. FIG. 3 is a partially omitted vertical cross-sectional view cut by a through hole 3 showing a filling step of filling the sealing resin composition 1 into a resin inflow space 5. 3 is a partially omitted longitudinal sectional view showing a process of separating a metal mask plate 4 from a sealing resin composition 1 attached to a piezoelectric substrate 2. FIG. 2 is a partially omitted vertical cross-sectional view showing a state where a piezoelectric substrate 2 is resin-sealed with a sealing resin composition 1 of Example 1. FIG. 3 is a partially omitted longitudinal sectional view showing a state in which a piezoelectric substrate 2 is sealed with a sealing resin composition 1 of Comparative Example 1. FIG. 2 is a partially omitted vertical cross-sectional view showing a state where a piezoelectric substrate 2 is resin-sealed with a sealing resin composition 1 of Example 1. FIG. It is a longitudinal cross-sectional view of the screen printing process which adheres the sealing resin composition 106 to the circumference | surroundings of the electronic component 120 using the conventional metal mask plate 103. FIG. It is a longitudinal cross-sectional view which shows the state which pulled the metal mask plate 103 completely away from the sealing resin composition 106 adhering to the electronic component 120. FIG.

1 Sealing resin composition 2 Piezoelectric substrate (electronic component)
11 Touch panel (substrate)

Claims (1)

Is a solid wear on the touch panel of the touch panel input device, is deposited as an ink screen printing ambient piezoelectric substrate touch panel input device vibrates when detecting the input operation, the resin sealing the piezoelectric base plate by being heated and cured A sealing resin composition for electronic parts,
Electronic component encapsulating resin composition, epoxy resin sealing agent (A), a silicone resin filler is an organic filler (B), the entire molten silica filler is an inorganic filler (C) 100 wt% And 10% by weight or 20% by weight of a silicone resin filler (B) and 40% by weight of a fused silica filler (C) in an epoxy resin sealing agent ( A ). electronic components Yofutome resin composition.

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