JP2002164480A - Method for covering electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for covering an electronic components with a silicon rubber wherein a main portion of the electronic components having electrodes protruding upwardly is covered with the silicon rubber except the electrodes, contamination of the electrodes due to the silicon rubber is reduced and soldering defects can be reduced thereafter. SOLUTION: The method for covering the electronic components with the silicon rubber comprises to cover the main portion except the electrodes of the electronic component with the electronic protruding upwardly with (A) an organic polysiloxane having at least two silicon atomic bond alkenyl groups in one molecule (B) an organic polysiloxane having at least two silicon atomic bond hydrogen atoms in one molecule and a content of the silicon atomic bond hydrogen atom is 0.9% or more and (C) a hydrosilylation reaction curing silicon rubber composition consisting of at least a platinum system catalyst, subsequently to cure only the composition covering the main portion by heating without curing the thin film composition on the surface of the electrodes and to clean with a solvent thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of coating an electronic component, and more particularly, to a method of coating an electronic component having an electrode protruding upward with only silicone rubber covering only the main part other than the electrode. The present invention relates to a method for coating an electronic component with a silicone rubber, which can reduce contamination of the electronic component and a subsequent poor soldering.

[0002]

2. Description of the Related Art A method of coating a main part other than an electrode of an electronic component having an electrode protruding upward with a hydrosilylation reaction-curable silicone rubber composition, and then heating the electronic component with the silicone rubber, Since the composition adhered to the electrode surface during coating or crawled on the electrode surface would also be cured, the electrode surface was contaminated with silicone rubber, and in subsequent soldering,
There was a problem that soldering could not be performed sufficiently.

In general, a hydrosilylation reaction-curable silicone rubber composition is uniformly cured by heating. Therefore, the composition of the main part of an electronic component is coated without curing the composition on the surface of the electrode protruding upward. It was difficult to cure only the composition.

[0004]

SUMMARY OF THE INVENTION The present inventors have found that (A) an organopolysiloxane having at least two silicon-bonded alkenyl groups in one molecule, and (B) at least two silicon atoms in one molecule. A hydrosilylation reaction-curable silicone rubber composition comprising an organopolysiloxane having a bonded hydrogen atom and having a silicon-bonded hydrogen atom content of 0.9% by weight or more, and (C) a platinum-based catalyst, comprises a thin film It is recognized that, depending on the heating conditions, there is a phenomenon that the curing speed is significantly slower than in the case of a thick film, and it is found that the above problem can be solved by using this phenomenon, and the present invention has been achieved. did.

[0005] That is, an object of the present invention is to cover only the main part of an electronic component having an electrode protruding upward except for the electrode with silicone rubber, to reduce contamination of the electrode by the silicone rubber, and to perform subsequent soldering. An object of the present invention is to provide a method of coating an electronic component with silicone rubber, which can reduce defects.

[0006]

According to the present invention, there is provided an electronic component having an electrode protruding upward, the main part other than the electrode being (A)
An organopolysiloxane having at least two silicon-bonded alkenyl groups in one molecule, (B) having at least two silicon-bonded hydrogen atoms in one molecule, and having a silicon-bonded hydrogen atom content of 0 0.9% by weight or more of an organopolysiloxane and (C) a hydrosilylation reaction-curable silicone rubber composition comprising at least a platinum-based catalyst. A method of coating an electronic component with a silicone rubber, comprising heating the composition to cure only the composition covering the main part, followed by solvent washing.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The method for coating an electronic component according to the present invention will be described in detail. The electronic components in the present method include a main part such as a semiconductor chip such as a monolithic IC, a hybrid IC, an LSI and a VLSI, a circuit board for the semiconductor chip, and the like.
And an electrode that protrudes upward, such as a wire, a beam lead, or a bump, as an electrical extraction portion. One example of such an electronic component is shown in FIG.

The electronic component shown in FIG. 1 is a monolithic I
C, the bonding pads 2 on the surface of the semiconductor chip 1
A gold bump 3 for electrical connection with an external circuit board is formed on the substrate. Further, in addition to the bonding pads 2, a passivation film 4 made of a polyimide resin may be formed on the surface of the semiconductor chip 1. The main part around the semiconductor chip 1 is covered with the silicone rubber 5. The silicone rubber is in the form of a gel having a relatively low hardness to a rubber having a high hardness.

In the present method, (A) an organopolysiloxane having at least two silicon-bonded alkenyl groups in one molecule is used as a hydrosilylation-curable silicone rubber composition for forming the silicone rubber 5.
(B) At least two silicon-bonded hydrogen atoms in one molecule, and the content of the silicon-bonded hydrogen atoms is 0.9.
By weight organopolysiloxane, and (C)
It is characterized by using a composition comprising at least a platinum-based catalyst. When such a composition is formed into a thin film, there is a phenomenon that the curing speed is significantly slower than that in the case of a thick film due to heating conditions. Therefore, in the present method, the composition in the form of a thin film on the electrode surface is cured. Only the composition covering the main part of the electronic component can be cured by heating so as not to cause the curing, and the composition on the electrode surface can be removed by the solvent cleaning by the subsequent solvent cleaning.

The organopolysiloxane of the component (A) is characterized by having at least two silicon-bonded alkenyl groups in one molecule. As this alkenyl group,
Examples include a vinyl group, an allyl group, a butenyl group, and a pentenyl group, and a vinyl group is preferable. Further, as the organic group having a silicon atom bond other than the alkenyl group in the component (A),
Alkyl groups such as methyl group, ethyl group and propyl group; aryl groups such as phenyl group and tolyl group; aralkyl groups such as benzyl group and phenethyl group; and halogenated alkyl groups such as 3,3,3-trifluoropropyl group. Is exemplified. Examples of the molecular structure of the component (A) include linear, partially branched linear, branched, and resinous structures.

The organopolysiloxane of the component (B) has at least two silicon-bonded hydrogen atoms in one molecule. The organic group having a silicon atom bond in the component (B) includes alkyl groups such as methyl group, ethyl group and propyl group; aryl groups such as phenyl group and tolyl group; aralkyl groups such as benzyl group and phenethyl group; Examples thereof include a halogenated alkyl group such as a 3,3-trifluoropropyl group. Examples of the molecular structure of the component (B) include linear, partially branched linear, branched, and resinous structures, and are preferably linear. Further, the content of silicon-bonded hydrogen atoms in the component (B) is at least 0.9% by weight, preferably 1.
It is at least 0% by weight, particularly preferably at least 1.2% by weight. This is because, when the content of silicon-bonded hydrogen atoms is increased as in the above range, when the obtained silicone rubber composition is formed into a thin film, the phenomenon that the curing rate is slowed becomes remarkable. Examples of the organopolysiloxane of the component (B) include a methylhydrogenpolysiloxane capped at both ends of a molecular chain with a trimethylsiloxy group, and a dimethylsiloxane / methylhydrogensiloxane copolymer capped at both ends of a molecular chain with a trimethylsiloxy group. . The content of the component (B) is not particularly limited as long as it is an amount that cures the composition, but the amount of the silicon-bonded hydrogen atom in the component (B) is 0 based on 1 mol of the alkenyl group in the component (A). The amount is preferably from 0.1 to 10 mol.

The platinum catalyst of the component (C) is a catalyst for promoting the hydrosilylation reaction between the alkenyl group in the component (A) and the silicon-bonded hydrogen atom in the component (B). Examples thereof include an alcohol solution of chloroplatinic acid, an olefin complex of platinum, an alkenylsiloxane complex of platinum, and a carbonyl complex of platinum. The content of the component (C) is not particularly limited as long as it is an amount that cures the composition.
The amount is preferably 0 ppm.

In the composition, other optional components include aromatic solvents such as toluene and xylene; hexane;
Solvents such as aliphatic solvents such as heptane and octane; fillers such as dry silica, wet silica, quartz and titanium oxide; coloring agents such as carbon black and iron oxide; heat conductive fillers such as alumina and boron nitride; Conductive fillers such as silver and copper; 3-
Methyl-1-butyn-3-ol, 3-phenyl-1-
It may contain a reaction inhibitor such as butyn-3-ol; an adhesion-imparting agent such as 3-methacryloxypropyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane; and a flame retardant. In particular, when the viscosity of the composition is high, the composition is preferably diluted with a solvent.

In the present method, first, a main part other than the electrode of an electronic component having an electrode protruding upward is coated with the composition. The method of coating the main part with the composition is not limited, and includes, for example, a potting method, a casting method, a dipping method, a dispensing method, an injection method, a spray method, and a spin coating method.
Preferably, a dispense method is used.

Next, the composition in the form of a thin film on the electrode surface is heated so as not to cure, and only the composition covering the main part is cured. The heating temperature is not limited,
When cured at a relatively low temperature, the curing rate of the composition in the form of a thin film on the electrode surface is significantly slower than that of the composition covering the main part of the electronic component. The temperature is preferably in the range of 60 to 140 ° C.

Next, in the present method, the composition on the electrode surface is removed by solvent washing. This solvent is not limited, for example, aromatic solvents such as toluene and xylene;
Aliphatic solvents such as hexane, heptane and octane; alicyclic solvents such as cyclohexane; petroleum solvents such as isoparaffin; low molecular siloxanes such as cyclic siloxane oligomers and linear siloxane oligomers; System solvents. The method of solvent-cleaning the composition on the electrode surface is not limited, and examples thereof include shower cleaning with a solvent, spray cleaning with a solvent, and immersion cleaning in a solvent. At this time, the solvent may be heated in order to increase the efficiency of cleaning, and when immersing in the solvent for cleaning, ultrasonic vibration or mechanical vibration may be applied. Thereafter, if necessary, the solvent is removed by heating to obtain an electronic component in which only the main part of the electronic component is covered with silicone rubber.

[0017]

EXAMPLES The method for coating an electronic component according to the present invention will be described in detail with reference to examples. The viscosities in the examples are values at 25 ° C., and the contamination rate of the electrodes and the defective rate of soldering of electronic components were determined as follows.

[Electrode Contamination Rate] Whether or not the electrode surface was covered with silicone rubber was observed with a micrograph to determine the contamination rate of the silicone rubber electrode.

[Soldering Defective Rate] As shown in FIG. 2, the gold bump 3 of the monolithic IC shown in FIG. 1 was surface-mounted on the test board circuit wiring 7 on the surface of the test board substrate 6 and soldered. . After performing 20 thermal cycle tests on the 20 test board substrates 6 on which the electronic components are mounted in this manner, one cycle of -65 ° C. for 30 minutes and + 150 ° C. for 30 minutes, the test board external leads 8 The electrical continuity test was performed, and the percentage of defective soldering was determined from the ratio of test board substrates having poor continuity.

Embodiment 1 Monolithic I shown in FIG.
In C, dimethylpolysiloxane endblocked by dimethylvinylsiloxy groups at both ends of the molecular chain, (CH ₃ ) ₂ (CH ₂ ＣＨCH) Si
Organopolysiloxane resin composed of O _1/2 unit and (CH ₃ ) ₃ SiO _1/2 unit and SiO _4/2 unit, trimethylsiloxy group-blocked methyl hydrogen polysiloxane having both ends of molecular chain (containing silicon-bonded hydrogen atom Amount = 1.5% by weight:
1,3-divinyltetramethylsiloxane of platinum, in which the silicon-bonded hydrogen atoms in the component are 1.5 moles per mole of the total vinyl groups in the dimethylpolysiloxane and organopolysiloxane resin. Hydrosilyl comprising a complex (an amount of 10 ppm by weight of platinum metal based on the composition) and 3-phenyl-1-butyn-3-ol (an amount of 150 ppm by weight based on the composition) A silicone rubber composition having a viscosity of 20 mPa · s was prepared by dissolving the silicone rubber composition in a hexane at a weight ratio of 2: 1.
The silicone rubber composition was applied by a dispenser to half the height of the gold bump 3 and then heated at 110 ° C. for 10 minutes. Observation of this electronic component confirmed that the surface of the gold bump 3 was covered with the thin-film silicone rubber composition. Thereafter, the electronic component was shower-washed with toluene for 1 minute to remove the silicone rubber composition on the surface of the gold bump 3, and then further washed at 150 ° C. for 1 minute.
Heated for hours. For this electronic component, the contamination rate of the electrode,
Table 1 shows the defective rates of soldering.

Comparative Example 1 In Example 1, the silicone rubber composition was applied by a dispenser to half the height of the gold bump 3 and then heated at 150 ° C. for 1 hour.
Observation of this electronic component confirmed that the surface of the gold bump 3 was covered with a thin film of silicone rubber. Thereafter, the electronic component was shower-washed with toluene for 1 minute, and further heated at 150 ° C. for 1 hour. Table 1 shows the contamination rate of the electrode and the defective rate of the soldering of this electronic component.

Comparative Example 2 Monolithic I shown in FIG.
In C, dimethylpolysiloxane endblocked by dimethylvinylsiloxy groups at both ends of the molecular chain, (CH ₃ ) ₂ (CH ₂ ＣＨCH) Si
An organopolysiloxane resin comprising O _1/2 units, (CH ₃ ) ₃ SiO _1/2 units and SiO _4/2 units, a dimethylsiloxane / methylhydrogensiloxane copolymer having a trimethylsiloxy group at both ends of a molecular chain (silicon atom Bonded hydrogen atom content = 0.75% by weight: 1.5 moles of silicon-bonded hydrogen atoms in this component per 1 mole of the total vinyl groups in the dimethylpolysiloxane and organopolysiloxane resin. Amount), 1,3-divinyltetramethylsiloxane complex of platinum (an amount of 10 ppm by weight of platinum metal with respect to this composition), and 3-phenyl-1
A hydrosilylation-curable silicone rubber composition comprising -butyn-3-ol (an amount of 150 ppm by weight based on the composition) was dissolved in hexane at a weight ratio of 2: 1 and had a viscosity of 20 mPa. The silicone rubber composition of s was applied by a dispenser to half the height of the gold bump 3 and heated at 110 ° C. for 10 minutes. Observation of this electronic component confirmed that the surface of the gold bump 3 was covered with a thin film of silicone rubber. After that, the electronic parts are shower-washed with toluene for 1 minute,
Furthermore, it heated at 150 degreeC for 1 hour. Table 1 shows the contamination rate of the electrodes and the defective rate of soldering for this electronic component.
It was shown to.

[0023]

[Table 1]

[0024]

According to the method of coating an electronic component of the present invention, only the main part other than the electrode of an electronic component having an electrode protruding upward is coated with silicone rubber to reduce contamination of the electrode by silicone rubber. There is a feature that subsequent soldering failure can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a monolithic IC which is an example of an electronic component according to the present invention.

FIG. 2 is a cross-sectional view of a test board substrate on which a monolithic IC as an example of an electronic component according to the present invention is mounted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor chip 2 Bonding pad 3 Bump 4 Passivation film 5 Silicone rubber 6 Test board substrate 7 Test board circuit wiring 8 Test board external lead

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Minoru Isshiki 2-2 Chikusa Beach, Ichihara City, Chiba Prefecture Toray Dow Corning Silicone Co., Ltd. 2 Toray Dow Corning Silicone Co., Ltd. Research and Development Headquarters (72) Inventor Katsumi Mine 2-2 Chigusa Coast, Ichihara City, Chiba Prefecture Toray Dow Corning Silicone Co., Ltd. Research and Development Headquarters F-term (reference) 4D075 BB26Z BB65Z CA34 DA07 DA36 DB01 DB31 DC22 EA05 EA19 EB43 EB52 EB56 EC54 EC60 4M109 AA01 BA03 CA05 DA09 DB15 EA10 EB04 EC20

Claims (1)

[Claims] 1. An electronic component having an electrode protruding upward, the main part other than the electrode is composed of (A) an organopolysiloxane having at least two silicon-bonded alkenyl groups in one molecule, and (B) one molecule An organopolysiloxane having at least two silicon-bonded hydrogen atoms therein and having a silicon-bonded hydrogen atom content of 0.9% by weight or more;
And (C) coating with a hydrosilylation reaction-curable silicone rubber composition comprising at least a platinum-based catalyst,
A method for coating an electronic component with a silicone rubber, comprising heating the thin film composition on the electrode surface so as not to cure the composition and curing only the composition covering the main part, followed by solvent washing. .