JP2010118429A - Electronic apparatus and manufacturing method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress an increase in electrical connection-resistance value between an electronic component and a substrate via a conductive adhesive even if the conductive adhesive has a temperature exceeding a glass transition point in an electronic apparatus in which the substrate and the electronic component that are connected via the conductive adhesive are sealed by a mold resin via an adhesion contributing agent. <P>SOLUTION: Each diameter of voids existing in an adhesion contributing agent 50 located around an electronic component 20 is set to ≤100,000 μm<SB>2</SB>or the film thickness of the adhesion contributing agent 50 located around the electronic component 20 is set to ≤20 μm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electronic device in which a substrate and an electronic component connected via a conductive adhesive are sealed with a mold resin, and a method for manufacturing such an electronic device. The present invention relates to an adhesion contributing agent that is applied to a substrate before resin sealing in order to ensure adhesion.

Conventionally, as this type of electronic device, an electronic component is mounted on one surface of a substrate via a conductive adhesive, and after electrically connecting the electronic component and the substrate via a conductive adhesive, An adhesion contribution agent is applied to a substrate and an electronic component on the substrate and sealed with a mold resin (for example, see Patent Document 1). In such an electronic device, the adhesion contributing agent is interposed between one surface of the substrate, the electronic component and the conductive adhesive, and the mold resin, thereby ensuring the adhesion of the mold resin.
JP-A-9-189997

  By the way, the adhesion contributing agent is used for improving the adhesion between the substrate and the mold resin and for relaxing internal stress. Usually, the adhesion contributing agent is diluted with a solvent and used. However, in order to increase the film thickness, the degree of dilution is not increased as much as possible, and it is applied thickly and then cured.

  According to the study of the present inventor, in the step of applying and curing the adhesion contributing agent, the adhesion contributing agent is also applied to the conductive adhesive that is the connection part of the electronic component, so that the electrical property of the conductive adhesive is reduced. A problem that the typical connection resistance value increased occurred.

  Furthermore, as a result of investigation by the present inventors, the cause of the increase in the connection resistance value described above is that the interface between the conductive adhesive and the substrate peels off due to the following two factors (a) and (b). I found out.

  (A) The void in the adhesion contributing agent generated around the electronic component due to the curing of the adhesion contributing agent expands due to the heat of the curing, and stress that pushes up the electronic component is generated by the expansion of the void. (B) At the curing temperature of the adhesion contributing agent, the conductive adhesive becomes a temperature equal to or higher than the glass transition point (Tg), and the connection strength of the conductive adhesive is lowered (see FIGS. 7 to 9 described later).

  Here, it is inevitable that the connection strength of the conductive adhesive is lowered due to the curing temperature of the adhesion contributing agent. Therefore, the present inventor said that it is important to reduce the above-mentioned stress applied to the electronic component by the adhesion contributing agent even if the conductive adhesive becomes higher than the glass transition point due to the curing temperature of the adhesion contributing agent. Reached new findings.

  The present invention has been made in view of the above problems, and in an electronic device in which a substrate and an electronic component are connected via a conductive adhesive and sealed with a mold resin via an adhesion contributing agent. An object of the present invention is to suppress an increase in the electrical connection resistance value between the electronic component and the substrate via the conductive adhesive even when the conductive adhesive becomes higher than the glass transition point.

  In order to achieve the above-mentioned purpose, the factors that reduce the stress applied to the electronic component by the adhesion contributing agent are focused on the following two points: the size of the void generated in the adhesion contributing agent and the film thickness of the adhesion contributing agent. These two points were examined experimentally. The inventions according to claims 1 to 3 have been obtained as a result of such experimental investigation.

That is, in the invention described in claim 1, voids are present inside the adhesion contributor (50) located around the electronic component (20), and the diameter of the voids is 100000 μm ² or less. It is characterized by.

As in the present invention, if the diameter of the void existing in the adhesion contributing agent (50) located around the electronic component (20) is 100000 μm ² or less (see FIG. 10 described later), the adhesion contributing agent (50 The electrical connection between the electronic component (20) and the substrate (10) via the conductive adhesive (30) even if the conductive adhesive (30) is above the glass transition point at the curing temperature of An increase in resistance value can be suppressed.

  The invention according to claim 2 is characterized in that the film thickness of the adhesion contributing agent (50) located around the electronic component (20) is 20 μm or less.

  If the film thickness of the adhesion contributing agent (50) located around the electronic component (20) is 20 μm or less as in the present invention (see FIG. 11 described later), the curing temperature of the adhesion contribution agent (50) is used. Even if the conductive adhesive (30) becomes higher than the glass transition point, an increase in electrical connection resistance value between the electronic component (20) and the substrate (10) via the conductive adhesive (30) is suppressed. can do.

  Invention of Claim 3 concerns on a manufacturing method, and before sealing with mold resin (40), the dilution rate of the adhesion | attachment contribution agent (50) apply | coated is diluent 2 with respect to stock solution 1. Further, the stock solution is obtained by dissolving polyetheramideimide in diglyme, and the weight ratio of these polyetheramideimide and diglyme is 10:90 to 20:80. And the diluent is diglyme.

As in the present invention, the adhesion contribution agent (50) to be applied is composed of such a stock solution and a diluent, and the dilution rate is equal to or greater than the weight ratio of the diluent 2 to the stock solution 1. The diameter of the void existing inside the adhesion contributing agent (50) located around the electronic component (20) should be 100000 μm ² or less, and the film thickness of the adhesion contribution agent (50) should be 20 μm or less. Therefore, even if the conductive adhesive (30) becomes a glass transition point or higher at the curing temperature of the adhesion contributing agent (50), the electronic component (30) via the conductive adhesive (30) 20) and the increase in the electrical connection resistance value between the substrate (10) can be suppressed.

  In addition, the code | symbol in the bracket | parenthesis of each means described in the claim and this column is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, parts that are the same or equivalent to each other are given the same reference numerals in the drawings for the sake of simplicity.

  FIG. 1 is a diagram showing a schematic cross-sectional configuration of an electronic device according to an embodiment of the present invention. The electronic device of the present embodiment is used, for example, in an ECU of an automobile, and is largely connected to the substrate 10, the electronic component 20 mounted on the base 10, and the electronic component 20 and the substrate 10. The conductive adhesive 30 includes a mold resin 40 that seals the members 10 to 30, and an adhesion contributing agent 50 that ensures adhesion between the members 10 to 30 and the mold resin 40.

  Although it does not specifically limit as the board | substrate 10, Various circuit boards, such as a ceramic board | substrate and a printed circuit board, and a wiring board are mentioned. The electronic component 20 may be anything as long as it is surface-mounted by the conductive adhesive 30 on one surface (the upper surface in FIG. 1) of the substrate 10. For example, as the electronic component 20, an IC chip, a diode, Examples include capacitors and resistors.

  The conductive adhesive 30 is a general one of this type, and specifically, a composition comprising a binder resin such as epoxy and a conductive filler such as Ag. The mold resin 40 is a mold material such as a general epoxy resin, and is molded by a transfer mold method or the like.

  Further, the adhesion contributing agent 50 is used as a primer for the mold resin 40. The function of the adhesion contributing agent 50 is to improve the adhesion between the substrate 10 and the mold resin 40 and to relieve internal stress.

  For example, as the adhesion contributing agent 50, there are thermosetting resins such as polyetheramide imide (PAI), polyamide (PA), and polyimide (PI), and a polymer resin is generally used. The adhesion contributing agent 50 is disposed by applying a liquid material by potting or printing and curing it.

  Here, for the adhesion contribution agent 50 to be applied, a solution obtained by dissolving a polymer resin such as PAI in a solvent such as diglyme or NMP is used as a stock solution, but here, diglyme or NMP is diluted. A solution obtained by diluting the stock solution with the diluent is applied.

  In such an electronic device, the electronic component 20 is mounted on one surface of the substrate 10 via the conductive adhesive 30, and after bonding with the conductive adhesive 30, the adhesion contributing agent 50 is applied and cured thereon. And then, sealing with mold resin 40 is performed.

In this embodiment, in the completed electronic device, in the adhesion contributing agent 50 positioned around the electronic component 20, the diameter of the void existing therein is set to 100000 μm ² or less.

  Since the adhesion contributing agent 50 is formed by applying and curing a liquid material as described above, voids in which the diluent is vaporized are present in the inside. The void is generated by vaporization of the diluent, and naturally forms a spherical shape. Therefore, the diameter of the void is the diameter of the void.

Moreover, in this embodiment, the film thickness of the adhesion | attachment contribution agent 50 located in the circumference | surroundings of the electronic component 20 is 20 um or less in the electronic device after completion. Here, in this embodiment, the configuration having a film thickness of 20 μm or less and the configuration having the void diameter of 100000 μm ² or less may be compatible, but only one of the configurations may be realized. . These configurations are based on experiments conducted by the present inventors, and this examination will be described next.

  FIG. 2 is a schematic plan view showing a sample used in an experiment conducted by the present inventor, and FIG. 3 is a partial schematic cross-sectional view of the sample. Here, the ceramic substrate 10 was used as the substrate 10.

  First, as shown in FIGS. 2 and 3, the ceramic substrate 10 and the electronic component 20 were connected by a conductive adhesive 30. The ceramic substrate 10 has a size of 1 inch □, a thickness of 1 mm, a material of alumina, and an Au plating 11 is applied to one surface on which the electronic component 20 is mounted. The electronic component 20 is a multilayer ceramic capacitor, the size is 3.2 × 1.6 × 1.25 mm, and the electrode material is Ag / Pd.

  <Adhesive curing>: A conductive adhesive 30 is printed on the substrate 10 using a metal mask (not shown) having a printed pattern opened, and the electronic component 20 is mounted with no load. 30 is cured. The printed film thickness of the conductive adhesive 30 is 60 μm, and the curing condition is 150 ° C. × 30 minutes curing.

  <First connection resistance measurement>: After the conductive adhesive 30 is cured, a first connection resistance measurement is performed. FIG. 4 is a schematic cross-sectional view showing a method for measuring an electrical connection resistance value between the electronic component 20 and the substrate 10 via the conductive adhesive 30, that is, a connection resistance.

  As shown in FIG. 4, measurement is performed by a four-terminal method using a constant current source K1 and a digital multimeter K2. The current is 10 mA, the voltage is measured, and the resistance value is obtained from the relationship of R = V / I. This is the connection resistance of the conductive adhesive 30. With this method, the first connection resistance, that is, the initial connection resistance is measured for the manufactured sample.

  As shown in FIG. 5, the heat-resistant tape M is applied to the sample after the measurement, and masking is performed. FIG. 5 is a schematic plan view showing a state where the heat-resistant tape M is attached. In order to measure the connection resistance, a part of the gold plating 11 on one surface of the substrate 10 to which the terminal is applied is covered with a heat-resistant tape M so that the adhesion contributing agent 50 is not applied.

  <Adhesion Contribution Agent Application>: Next, PAI is applied as an adhesion contribution agent 50 to one surface of the substrate 10, the electronic component 20, and the surface of the conductive adhesive 30. Here, the PAI to be applied is obtained by further diluting a stock solution in which diglyme is dissolved with diglyme as a diluent. Specifically, as a stock solution, HL1210-ND5 (trade name, weight ratio manufactured by Hitachi Chemical Co., Ltd.) is used. PAI: diglyme = 10: 90 to 20:80) was used.

  And as a dilution rate which is a weight ratio of an undiluted solution and a diluent (diglyme), four types, undiluted solution, 1: 1, 1: 2, and 1: 3 were used as undiluted solution: diluent. The adhesion contributing agent 50 having such a dilution rate is applied little by little to the center of the substrate 10 shown in FIG. 2 by dispensing, and is wrapped around the electronic component 20 as shown in FIG.

  <Left>: After the application of the adhesion contributing agent 50 is completed, the workpiece is left in the air for 1 hour.

  <Primary curing (drying)>: After the standing, the primary curing is performed for the purpose of drying the adhesion contributing agent 50. The condition is 80 ° C. × 30 minutes on a hot plate.

  <Second measurement of connection resistance>: After this primary curing, the heat-resistant tape M is peeled off, the probe is applied to the gold plating 11 of the substrate 10 where the adhesion contributing agent 50 is not attached, and the second time by the above four-terminal method. Measure the connection resistance.

  <Secondary curing (main curing)>: Next, secondary curing is performed for the purpose of main curing the adhesion contributing agent 50. The condition is 150 ° C. × 3 hours in a thermostatic bath.

  <Connection resistance measurement third time>: After this secondary curing, a probe is applied to the gold plating 11 of the substrate 10 where the adhesion contributing agent 50 is not attached, and the third connection resistance is measured by the above four-terminal method.

  FIG. 7 shows the connection resistance after the adhesive curing (initial connection resistance), the connection resistance after primary curing (second connection resistance), and the connection resistance after secondary curing for each dilution ratio of the adhesion contributing agent 50. It is a figure which shows the measurement result of (3rd connection resistance).

  As shown in FIG. 7, when the stock solution was applied as the adhesion contributing agent 50, the connection resistance value greatly increased after the secondary curing. Further, the connection resistance value did not increase as the dilution rate increased.

  <Observation of Hardening Behavior of Adhesion Contributing Agent>: Further, in order to examine the curing behavior of the adhesion contributing agent 50, the electronic component 20 is placed on one surface of the ceramic substrate 10 without being connected by the conductive adhesive 30, and the same as described above. Adhesion-contributing agent 50 made of PAI was applied, and primary curing (80 ° C. × 30 minutes) and secondary curing (150 ° C. × 3 hours) were performed in the same manner as described above, and the curing behavior in this step was visually observed. did.

  As a result, it was found that voids were generated in the adhesion contribution agent 50 located around the electronic component 20 by primary curing, and the voids were expanded by secondary curing. Further, it was confirmed that the electronic component 20 was displaced due to the generation of voids in the primary curing, the stress was generated by the void expansion in the secondary curing, and the electronic components 20 were lifted.

  <High-temperature shear strength test>: As shown in FIG. 7 and the observation of curing behavior, an increase in connection resistance occurs after secondary curing, so it is considered that some phenomenon has occurred during secondary curing. It is done. Therefore, a high temperature shear test was performed on an uncoated sample of the adhesion contributing agent. This uncoated sample is one in which the adhesion contributing agent is not applied to the sample after curing of the conductive adhesive, that is, as shown in FIG.

  FIG. 8 is a diagram showing the results of measuring the initial connection resistance, the connection resistance at 130 ° C., the connection resistance at 150 ° C., and the connection resistance at 170 ° C. by the above four-terminal method for this uncoated sample. . It can be seen that the shear strength of the conductive adhesive 30 decreases as the temperature rises.

  In addition, the above-mentioned uncoated samples were further sheared at room temperature for three types of samples: those immersed in diglyme, coated with PAI stock solution, and coated with PAI diluted 1: 2. A strength test was performed. The result is shown in FIG. In FIG. 9, the connection resistance does not substantially change from the initial stage for any sample.

  From the results shown in FIGS. 8 and 9, the decrease in the shear strength of the conductive adhesive 30 is not a change in the physical properties of the conductive adhesive 30 due to immersion in diglyme and application of PAI, but a high temperature of 150 ° C. Therefore, it is presumed that the adhesive strength of the conductive adhesive 30 was lowered because the conductive adhesive 30 exceeded its glass transition temperature (Tg).

  <Cross-section examination>: Further, in order to investigate the cause of the increase in the connection resistance value, a cross-section examination by microscopic observation was performed. The cross-sectional examination was performed about the sample which applied undiluted | stock solution as the adhesion | attachment contribution agent 50, the connection resistance value increased, the sample whose dilution rate was high and the connection resistance value did not increase, and the above-mentioned uncoated sample.

  FIG. 10 is a cross-sectional view schematically showing the result of cross-sectional examination. For the sample in which the stock solution is applied and the connection resistance value is increased, peeling H occurs at the interface between the conductive adhesive 30 and the substrate 10, and in the adhesion contributing agent 50 located around the electronic component 20. It was confirmed that a huge void B was present.

  From the inventors' experiments as described above, the cause of the increase in the connection resistance is that the PAI film is formed on the surface of the adhesion contributing agent 50 in the primary curing, and the temperature of the conductive adhesive 30 is increased in the secondary curing. Since the Pg film formed by the primary curing reduces the connection strength due to the conductive adhesive 30, solvent components such as a diluent that cannot be volatilized become voids. It is presumed that this is caused by the generation of stress that occurs around and pushes up the electronic component 20.

  Therefore, since it is inevitable that the adhesion force of the conductive adhesive 30 is reduced due to the curing temperature of the adhesion contributing agent 50, attention was focused on reducing the stress caused by the adhesion contributing agent 50. And as the factor, we focused on two points, the size of the void B and the film thickness of the adhesion contributing agent 50, and investigated them.

  In order to determine the application / curing conditions of the adhesion contributing agent 50 in which the connection resistance value does not increase using the same sample as in the above experiment, the application / curing is performed by changing the dilution rate of the adhesion contributing agent 50, and the surroundings of the electronic component 20 The relationship between the size of the void B generated in the film and the film thickness of the adhesion contributing agent 50 and the connection resistance value was investigated.

  FIG. 11 is a diagram showing the relationship between the void size and the connection resistance value, and FIG. 12 is a diagram showing the relationship between the film thickness of the adhesion contributing agent 50 and the connection resistance value.

  In both FIG. 11 and FIG. 12, the dilution rate is shown by changing the type of the plot, a round plot (stock solution without dilution), a triangular plot (stock solution: diluent = 1: 1), and a rhombus plot (stock solution: diluent). = 1: 2), square plot (stock solution: diluent = 1: 3). For each dilution rate, the n number is 30, but it is difficult to see all the results. Therefore, in FIG. 11 and FIG. 12, the number of plots is reduced and typical values are plotted.

As shown in FIG. 11, in the adhesion contribution agent 50 positioned around the electronic component 20, it has been found that the connection resistance value hardly increases if the diameter of the void existing therein is 100000 μm ² or less.

  Further, as shown in FIG. 12, it was found that the connection resistance value hardly increased when the film thickness of the adhesion contributing agent 50 after the secondary curing was 20 μm or less. The above is a study conducted by the present inventors. Based on the results of these experiments, the electronic device of this embodiment defines the void diameter and the film thickness of the adhesion contributing agent 50 as described above.

Moreover, as shown in FIG. 11 and FIG. 12, if the dilution ratio of the adhesion contribution agent 50 to be applied is equal to or greater than the weight ratio of the diluent 2 to the stock solution 1, the void diameter is 100,000 μm ² or less. The configuration with the film thickness of 20 μm or less is almost certainly realized.

  From this, as a manufacturing method of this embodiment, as the adhesion contribution agent 50 to be applied, polyetheramideimide is dissolved in diglyme, and the weight ratio of the polyetheramideimide and diglyme is 10: The stock solution that is a 90-20: 80 solution is further diluted with diglyme, which is a diluent, and the dilution ratio is preferably a weight ratio of diluent 2 or more with respect to the stock solution 1.

  In the above example, the curing conditions are primary curing 80 ° C. × 30 minutes, secondary curing 150 ° C. × 3 hours, but in order to further suppress the generation of voids, the primary curing time may be increased. . For example, 30 minutes is changed to 3 hours. Residual solvent can be reduced by lengthening the heating time at a low temperature in the primary curing. In that case, the secondary curing time may be short. For example, 3 hours is 30 minutes.

It is a schematic sectional drawing of the electronic device which concerns on embodiment of this invention. It is a schematic plan view which shows the sample used for the experiment which this inventor conducted. FIG. 3 is a partial schematic cross-sectional view of the sample shown in FIG. 2. It is a schematic sectional drawing which shows the measuring method of connection resistance. It is a schematic plan view which shows the affixing state of a heat resistant tape. It is a schematic sectional drawing which shows the state of the sample after adhesion | attachment contribution agent application | coating. It is a figure which shows the measurement result of each connection resistance after adhesive hardening at the time of changing the dilution rate of adhesion contribution agent, after primary hardening, and after secondary hardening. It is a figure which shows the result of having measured each connection resistance of an initial stage, 130 degreeC, 150 degreeC, and 170 degreeC about an uncoated sample. It is a figure which shows the result of a normal temperature shear strength test. It is a schematic sectional drawing which shows the result of a cross-sectional examination. It is a figure which shows the relationship between the magnitude | size of a void and a connection resistance value. It is a figure which shows the relationship between the film thickness of an adhesion | attachment contribution agent, and a connection resistance value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Board | substrate 20 Electronic component 30 Conductive adhesive 40 Mold resin 50 Adhesion contribution agent

Claims (3)

A substrate (10);
An electronic component (20) mounted on one surface of the substrate (10);
A conductive adhesive (30) interposed between the electronic component (20) and one surface of the substrate (10) to electrically connect these members (10, 20);
A mold resin (40) for sealing one surface of the substrate (10), the electronic component (20) and the conductive adhesive (30);
Adhering between one surface of the substrate (10), the electronic component (20) and the conductive adhesive (30) and the mold resin (40) to ensure adhesion of the mold resin (40) In an electronic device comprising a contributor (50),
An electronic device, wherein a void is present inside the adhesion contributing agent (50) located around the electronic component (20), and the diameter of the void is 100000 μm ² or less. A substrate (10);
An electronic component (20) mounted on one surface of the substrate (10);
A conductive adhesive (30) interposed between the electronic component (20) and one surface of the substrate (10) to electrically connect these members (10, 20);
A mold resin (40) for sealing one surface of the substrate (10), the electronic component (20) and the conductive adhesive (30);
Adhering between one surface of the substrate (10), the electronic component (20) and the conductive adhesive (30) and the mold resin (40) to ensure adhesion of the mold resin (40) In an electronic device comprising a contributor (50),
The electronic device according to claim 1, wherein a film thickness of the adhesion contributing agent (50) positioned around the electronic component (20) is 20 um or less. After electrically connecting the electronic component (20) to the one surface of the substrate (10) via the conductive adhesive (30), the one surface of the substrate (10), the electronic component (20), and the conductive adhesive An adhesion contributing agent (50) that secures the adhesion of the mold resin (40) is applied to the surface of (30) and cured, and then one surface of the substrate (10), the electronic component (20), and In the method of manufacturing an electronic device in which the conductive adhesive (30) is sealed with the mold resin (40),
The dilution ratio of the applied adhesion contributing agent (50) is not less than the weight ratio of the diluent 2 to the stock solution 1,
Further, the stock solution is obtained by dissolving polyetheramideimide in diglyme, and the weight ratio of these polyetheramideimide and diglyme is 10:90 to 20:80, and the diluent is diglyme. A method for manufacturing an electronic device, wherein:

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