JPH07207162A - Semiconductor rectifier coating protection agent - Google Patents

Abstract

(57) [Summary] [Structure] Alkenyl group-containing polyorganosiloxane,
A protective agent for a semiconductor rectifying device, which comprises polyorganohydrogensiloxane, a platinum-based catalyst, and titanium oxide powder. [Effect] It is excellent in workability and excellent in the effect of protecting the semiconductor rectifying element, and particularly imparts excellent salt damage resistance to the semiconductor rectifying element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating protective agent for coating and protecting a semiconductor chip of a semiconductor rectifying device.

[0002]

2. Description of the Related Art A three-phase full-wave rectifier for an AC generator for a vehicle includes a pair of heat radiating plates that serve as DC side terminals, and the rectifying directions within the heat radiating plates are aligned with respect to the heat radiating plates. In this case, the semiconductor rectifying elements are fixed to each other in three different rectifying directions, and the three AC side terminals are connected to the semiconductor rectifying elements fixed to different heat radiating plates.
As the semiconductor rectifying element, a resin-sealed type is used instead of the conventional can-sealed type due to progress in stabilization technology. Since this semiconductor rectifying element is used under severe conditions, various improvements have been added to the sealing resin. As a representative example of the sealing resin, Japanese Patent Laid-Open No. 59-59
(1) as described in Japanese Patent Publication No. 172749.
A combination of a silicone resin and (2) a silicone resin and an epoxy resin containing silica powder is known.

Silicone resins are widely used as sealing resins for semiconductor rectifiers because of their excellent heat resistance, moisture resistance and adhesion to metals. However,
Silicone resin has a large coefficient of thermal expansion, and in particular, in the case of a type that cures by a condensation reaction, the curing shrinkage is large, so that peeling easily occurs at the adhesive interface with the metal, and the electrical characteristics of the semiconductor rectifier are poor. May be caused.

The silicone resin, when used alone, has a problem of low salt damage resistance. That is, when the semiconductor rectifying device is placed in a salt spray state, alkali is generated by electrolysis of the salt, and this alkali breaks the silmetalloxane bond that contributes to the adhesion between the silicone resin and the metal, and the metal and the silicone resin. It causes peeling of the adhesive interface with. This is a serious problem for semiconductor rectifiers mounted on vehicles used in beach areas and snow areas.

The above-mentioned problems still exist even in the case of a combination of a silicone resin and an epoxy resin, that is, a structure in which an epoxy resin layer is laminated on a silicone resin layer. Since silicone resin has a larger coefficient of thermal expansion than epoxy resin, when a temperature cycle is applied, the silicone resin expands and contracts, causing peeling at the adhesive interface between the epoxy resin and the metal, and the adhesive interface between the silicone resin and the metal below it. Is because it is placed in almost the same state as when the silicone resin is used alone.

As described above, as long as a conventionally known resin is used as the sealing resin, a semiconductor rectifying element excellent in salt damage resistance has not been obtained.

Japanese Unexamined Patent Publication (Kokai) No. 4-146655 solves the problem of the conventional sealing silicone resin against salt damage, and a silicone resin containing silica powder is used as a sealing agent having excellent salt damage resistance. Is disclosed. The publication discloses adding 40 to 120 parts by weight of such silica powder to 100 parts by weight of the silicone resin. However, in the case of performing such high filling, if fine powder silica having a particle size of 5 to 40 nm such as fumed silica is used, the apparent viscosity of the system is extremely increased and the fluidity is lost, resulting in remarkable workability. Spoil. Further, fused silica and pulverized silica can be highly filled, but those having an average particle size of 2 to 6 μm, which are particularly desirable in the publication, have a large fluidity during the sealing operation and immediately thereafter. Since a dripping flow is generated, the workability is rather bad, and there is a problem that a part of the uncured silicone resin flows out when it is moved to the next step, for example, the heating step of heating and curing the treated silicone resin. Further, from the viewpoint of workability, a method of preparing a silicone composition in advance and storing it in a single container, and extruding or pouring a necessary amount to perform a sealing operation is preferable, but silica powder settles during storage. However, there is a problem of non-uniformity.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide excellent salt damage resistance and sealing workability without deteriorating the moisture resistance inherent to silicone, and to improve the exposed surface of a semiconductor chip in a semiconductor rectifying device. It is an object of the present invention to provide a coating protective agent containing a crosslinkable polyorganosiloxane suitable for coating protection.

[0009]

The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, in a coating protective agent containing polyorganosiloxane capable of being crosslinked by an addition reaction, titanium oxide was used as a filler. The inventors have found that the purpose can be achieved by using a powder, and have completed the present invention.

That is, the semiconductor rectifying element coating protective agent of the present invention comprises (A) the general formula:

[Chemical 3] (In the formula, R ¹ represents an alkenyl group; R ² represents a substituted or unsubstituted monovalent hydrocarbon group containing no aliphatic unsaturated bond; a is an integer of 1 to 3; b is 0. Is an integer of 2; and a + b is an integer of 1 to 3), and R ¹ is at least 2 in the molecule.
Viscosity at 25 ° C. of 50 to 1,000,0
00cSt alkenyl group-containing polyorganosiloxane 1
00 parts by weight; (B) General formula:

[Chemical 4] (In the formula, R ³ represents a substituted or unsubstituted monovalent hydrocarbon group; c is an integer of 0 to 2; d is an integer of 1 to 3; provided that c + d is an integer of 1 to 3. A polyorganohydrogensiloxane having an average number of hydrogen atoms bonded to silicon atoms of more than 2 in the molecule, the alkenyl group 1 in the component (A)
The amount of hydrogen atoms bonded to silicon atoms in the component (B) is 0.2 to 5 per (B) component; (C) a catalyst selected from the group consisting of platinum and platinum compounds; In contrast, 0.1 to 1,0 as a platinum atom
00 ppm; and (D) titanium oxide powder in an amount of 40 to 120 parts by weight.

The coating protective agent of the present invention has a suitable fluidity when used for coating semiconductor chips, and when heated,
Resin-like, rubber-like or gel-like, preferably rubber-like, which is crosslinked by an addition reaction between the alkenyl group of the component (A) and the hydrosilyl group of the component (B) and is composed of a crosslinked polyorganosiloxane and titanium oxide powder. Forming a coating-like protective layer.

The alkenyl group-containing polyorganosiloxane of the component (A) used in the present invention is the base polymer of the coating protective agent of the present invention, and contains a silicon atom in the siloxane unit represented by the above formula (I). It has an alkenyl group R ¹ directly attached. The siloxane skeleton of the component (A) may be linear, branched, cyclic or network, but when the coating protective agent after cross-linking has a rubber-like or gel-like structure, it may be linear or straight. It is preferably a mixture of chain and branched ones. Viscosity is 50 ~ at 25 ℃
1,000,000 cSt, 100 to 500,000
0 cSt is preferred. If it is less than 50 cSt, the crosslinked material is brittle,
If it exceeds 1,000,000 cSt, the flowability of the coating protective agent in the uncrosslinked state becomes poor and the workability becomes poor.

Examples of R ¹ include vinyl, allyl, 1-butenyl, 1-hexenyl and the like, and a vinyl group is preferable because of easy synthesis. Examples of the organic group bonded to the silicon atom of R ² and other siloxane units include
Alkyl groups such as methyl, ethyl, propyl, butyl, hexyl and dodecyl; aryl groups such as phenyl; 2-
Examples thereof include aralkyl groups such as phenylethyl and 2-phenylpropyl; substituted hydrocarbon groups such as chloromethyl and 3,3,3-trifluoropropyl. Of these, a methyl group is most preferred because it is easy to synthesize, has a degree of polymerization required for maintaining good physical properties after crosslinking, and retains a low viscosity before crosslinking.
A small amount of phenyl groups is required when the composition after crosslinking is required to have cold resistance, and 3,3,3- when it is required to have oil resistance.
It can be arbitrarily selected such as containing a trifluoropropyl group.

The siloxane unit represented by the formula (I) may be present at the terminal end of the molecular chain of the alkenyl group-containing polyorganosiloxane (A), in the middle thereof, or at both of them, but is crosslinked. In order to give the subsequent coating protective agent excellent mechanical properties, it is preferable to be present at least at the terminal. That is, taking the above into consideration, the component (A) is a polydimethylsiloxane whose both ends are blocked with dimethylvinylsiloxy groups, or a mixture containing this and a branched polysiloxane containing a dimethylvinylsiloxy group. It is particularly preferable that

In the polyorganohydrogensiloxane of the component (B) used in the present invention, the hydrogen atom bonded to the silicon atom is present in the siloxane unit represented by the formula (II), and the Si--H bond thereof is It is a component that acts as a cross-linking agent by an addition reaction with the alkenyl group in the component (A). The number of hydrogen atoms bonded to the silicon atom is more than 2 on average in the molecule as a whole of the component (B), and when mechanical strength is required, it is preferably 3 or more.
As the organic group of R ³ and other siloxane units,
The same as R ^{2 in the} component (A) is exemplified, and a methyl group is most preferable from the viewpoint of easy synthesis. In such a polyorganohydrogensiloxane, the siloxane skeleton may be linear, branched or cyclic. The viscosity of the component (B) is 10-1, at 25 ° C.
, 000,000 cSt is preferable, and 15 to 500 cSt is more preferable.

Specific preferred examples of the component (B) include the following. a. Branched polyorganohydrogensiloxane consisting of (CH ₃ ) ₂ HSiO _1/2 and SiO ₂ units b. Formula (III):

[0017]

[Chemical 5]

(In the formula, p is 3 to 100 and q is 0 to 100.
Represents an integer of), a linear polyorganohydrogensiloxane represented by the formula; c. The following formula (IV):

[0019]

[Chemical 6]

(In the formula, p is 1 to 100 and q is 0 to 100.
Represents an integer) of the linear polyorganohydrogensiloxane.

The amount of the component (B) blended is such that the number of hydrogen atoms bonded to silicon atoms in the component (B) is 0.2 to 5 with respect to one alkenyl group in the component (A). Since it is a large amount and a coating protective agent having excellent mechanical properties can be obtained, an amount of 0.5 to 3 is preferable. When the number of hydrogen atoms per one alkenyl group is less than 0.2, the crosslinking density becomes too low and the crosslinking does not proceed sufficiently, resulting in fluidity remaining after the crosslinking. It is not preferable because it cannot be obtained. On the other hand, if the number of hydrogen atoms exceeds 5, it is not preferable because foaming easily occurs during the crosslinking reaction, and the heat resistance of the coating protective agent after crosslinking decreases. Further, the component (B) preferably has excellent compatibility with the component (A).

The catalyst selected from the component (C) platinum and the platinum compound used in the present invention promotes the addition reaction between the alkenyl group of the component (A) and the hydrosilyl group of the component (B). Chloroplatinic acid, a complex obtained from chloroplatinic acid and an alcohol, a platinum-olefin complex, a platinum-vinylsiloxane complex, a simple substance of platinum (platinum black), other platinum coordination compounds, or a carrier of alumina, silica, etc. It is possible to use a single substance supported. Chloroplatinic acid or a platinum-olefin complex is preferably dissolved in an alcohol solvent, a ketone solvent, an ether solvent, a hydrocarbon solvent, or the like.

The amount of the component (C) blended is 0.1 to 1,000 ppm as platinum atom relative to the component (A).
The range of 0 to 100 ppm is preferred. If it is less than 0.1 ppm, the effect is small, and if it exceeds 1,000 ppm, no particular improvement in the crosslinking rate can be expected.

The titanium oxide powder of the component (D) used in the present invention is a characteristic component in the present invention, and is excellent in salt damage resistance, excellent sealing workability and preservation in the coating protective agent of the present invention. It is a component that imparts stability. The component (D) may be either rutile type or anatase type titanium oxide, and may be obtained by either the sulfuric acid method or the chlorine method. The average particle size is preferably 0.01 to 10 μm, 0.1 to 2 μm
m is more preferred. To increase the affinity with the component (A) or the component (B) and improve the stability of the dispersed state in the uncrosslinked system, trimethylchlorosilane, trimethylmethoxysilane, hexamethyldisilazane, hexamethylcyclotrisiloxane. Surface treatment with silanes, such as octamethylcyclotetrasiloxane, silazanes, and / or siloxanes is preferred, which has a small average particle size or is a commercially available oxidation product whose surface is treated with a hydrous oxide. Particularly effective in the case of titanium. From the viewpoint of suppressing the reverse leakage current of the semiconductor rectifier, the content of alkali metal ions such as sodium ions and potassium ions contained in the titanium oxide powder is preferably 10 ppm or less.

The blending amount of the component (D) is 100 parts of the component (A).
It is 40 to 120 parts by weight, and 50 to 100 parts by weight is preferable in order to provide excellent workability and excellent salt damage resistance to the semiconductor rectifier. If it is less than 40 parts by weight, sufficient salt damage resistance cannot be obtained, and the fluidity becomes large, resulting in poor workability. If it exceeds 100 parts by weight, the viscosity and thixotropic property become too large, resulting in poor workability.

The coating protective agent of the present invention may contain various additives, if necessary, as long as the object of the present invention is not impaired. For example, various pigments for the purpose of coloring; silane compounds or siloxane compounds having a carbon functional group such as (meth) acryloyl group or epoxy group for the purpose of imparting adhesiveness, or a side chain containing a trialkoxysilyl group and an ester bond. And an adhesiveness-imparting agent such as a cyclic siloxane having a hydrogen atom bonded to a cyclic silicon atom; a cross-linking reaction retarder for increasing the stability during storage at room temperature after the coating protective agent is prepared; In order to improve heat resistance, heat resistance improvers such as iron oxide, cerium oxide, iron carboxylate, and rare earth organic acid salts; and other known flame retardants can be added.

The coating protective agent of the present invention is prepared by uniformly mixing the components (A) to (D) in the presence or absence of a crosslinking reaction retarder using a mixing means such as a kneader, It can be stored in a single container at room temperature or low temperature, and this type is preferable from the viewpoint of workability. Further, a mixture containing a part of the component (A) and the component (B) and a mixture containing a part of the component (A) and the component (C) are prepared and mixed immediately before use to protect the coating. It may be used as an agent, in which case the component (D) may be blended in one or both mixtures, but usually it is distributed in both mixtures so that each mixture maintains a proper fluidity. To be done.

Although the coating protective agent of the present invention contains titanium oxide powder having a large specific gravity as a filler, unexpectedly, the filler precipitates even after long-term storage after preparation. The storage stability is excellent. It is considered that this is because the surface state of the titanium oxide powder has an effect.

The coating protective agent of the present invention is usually processed on the surface of a semiconductor chip by an extrusion, dropping or injection device, and causes a crosslinking reaction by heating to form a crosslinked body having a predetermined property. The heating condition is, for example, heating at 60 ° C. for several minutes to obtain a crosslinked body which does not flow and can retain its shape.

[0030]

The coating protective agent for a semiconductor rectifying device obtained by the present invention is not only excellent in alkali resistance and imparts excellent salt damage resistance to the rectifying device, but also causes sedimentation of the filler even after long-term storage. It does not cause separation and has excellent workability in processing semiconductor chips. Therefore, the coating protective agent of the present invention is extremely effective for coating and protecting the exposed surface of the semiconductor chip in various semiconductor rectifying elements, particularly in semiconductor rectifying elements used for rectification of vehicle alternators.

[0031]

EXAMPLES The present invention will be described in more detail below with reference to examples. The invention is not limited to these examples. In the examples and comparative examples, all parts are parts by weight.

In Examples and Comparative Examples, (A)-
As the component (D) and a silica-based filler for comparison,
The following materials were used. A-1: Polydimethylsiloxane having a viscosity of 3,000 cSt at 25 ° C. and having both ends blocked with dimethylvinyl groups; A-2: Viscosity at 25 ° C. of 200 cP, (CH ₃ ) ₃
Polyorganosiloxane consisting of 37 mol% of SiO _1/2 units, 56 mol% of SiO ₂ units and 7 mol% of (CH ₂ ═CH) CH ₃ SiO units; B-1: (CH ₃ ) ₂ HSiO _1/2 units 67 Polymethyl hydrogen siloxane composed of mol% and 33 mol% of SiO ₂ unit; C-1: platinum-vinylsiloxane complex solution, platinum atom content 0.5%; D-1: average particle size of 0.2 μm, Titanium oxide powder whose surface is treated with siloxane; S-1: fused silica having an average particle size of 4 μm; S-2: fumed silica having an average particle size of 0.015 μm and whose surface is treated with hexamethyldisilazane; M- 1: 3-methacryloxypropyltrimethoxysilane.

Examples 1 to 3 and Comparative Examples 1 to 5 The above various materials having the compositions shown in Table 1 were mixed at room temperature by a kneader until uniform, and Examples 1 to 3 and Comparative Examples 1 to 5 were mixed. A coating protective agent which was crosslinked by an addition reaction to give a rubber-like crosslinked product was prepared. After the coating protective agent was sealed and stored for 3 months, the degree of sedimentation of the filler was observed. The results are shown in Table 1.

As a rectifying element, a semiconductor chip having one main surface bonded to the bottom of a bowl-shaped metal container and having a pn junction, a header section bonded to the other main surface of the semiconductor chip, and the header section 2 extending vertically with it
A semi-finished product of a semiconductor rectifying device, which has a lead portion of a book and whose surface of a semiconductor chip is still exposed, was used. To embed the semiconductor chip and header of this rectifier,
Each of the above-mentioned coating protective agents was injected, and the workability during injection was observed. After 10 minutes from the injection, the bowl-shaped container was tilted and the flowability of the coating protective agent was observed. The results are shown in Table 1.

Then, at 70 ° C. for 1 hour, at 200 ° C. for 16 hours
By gradually heating for a period of time, the coating protective agent was cured into rubber by cross-linking, and the rectifying element for evaluation was completed.

The rectifying element was subjected to the following evaluation tests, and the results shown in Table 1 were obtained.

(1) Salt Damage Resistance 40 ml of a 10 wt% concentration aqueous sodium chloride solution was placed in a Pyrex beaker having a capacity of 100 ml, the rectifying element was immersed in this, and a voltage between electrodes of 12 V was applied in a reverse biased state to reverse electrical conductivity. The time at which the characteristics deteriorated was measured.

(2) Heat resistance The rectifying element was heated at 300 ° C. for 1 hour, and it was visually observed whether cracking occurred.

[0039]

[Table 1]

From these results, 40 parts by weight of titanium oxide was added to 100 parts by weight of vinyl group-containing polyorganosiloxane.
It has been revealed that the coating protective agent obtained by compounding 120 parts by weight has excellent workability and imparts excellent salt damage resistance to the semiconductor rectifier.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location C09D 183/05 PMT 183/07 PMU H01L 23/29 23/31

Claims (1)

[Claims] 1. (A) General formula: (In the formula, R ¹ represents an alkenyl group; R ² represents a substituted or unsubstituted monovalent hydrocarbon group containing no aliphatic unsaturated bond; a is an integer of 1 to 3; b is 0. Is an integer of 2; and a + b is an integer of 1 to 3), and R ¹ is at least 2 in the molecule.
Viscosity at 25 ° C. of 50 to 1,000,0
00cSt alkenyl group-containing polyorganosiloxane 1
00 parts by weight; (B) General formula: (In the formula, R ³ represents a substituted or unsubstituted monovalent hydrocarbon group; c is an integer of 0 to 2; d is an integer of 1 to 3; provided that c + d is an integer of 1 to 3. A polyorganohydrogensiloxane having an average number of hydrogen atoms bonded to silicon atoms of more than 2 in the molecule, the alkenyl group 1 in the component (A)
The amount of hydrogen atoms bonded to silicon atoms in the component (B) is 0.2 to 5 per (B) component; (C) a catalyst selected from the group consisting of platinum and platinum compounds; In contrast, 0.1 to 1,0 as a platinum atom
00 ppm; and (D) 40 to 120 parts by weight of titanium oxide powder.