JPH0240929A - Bonding wire coated with heat resisting polyurethane - Google Patents

Abstract

PURPOSE:To obtain the coating of a wire which is free from cracks and exfoliation even when the wire is bent, with the wire being coated with heat resisting polyurethane and used for the connection of a semiconductor device, by constituting the coating of a material produced by the reaction between a polyol component and isocyanate. CONSTITUTION:This coating material is produced by the reaction between a polymer component composed principally of terephthalic acid-based polyol containing activated hydrogen and isocyanate. Ethylene glycol, propylene glycol, glycerol, etc., are particularly suitable for the material constituting the polyol, and toluylenediisocyanate, xylylenediisocyanate, etc., are used for the isocyanate. In this case, a constituent derived from terephthalic acid is contained in the molecular skeleton of the reaction product and, when required, an appearance improving agent, dye, and hardening accelerating catalyst are added. Thus a coating having a high heat resisting property can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat-resistant polyurethane-coated bonding wire used for connecting semiconductor devices.

[Conventional technology]

2. Description of the Related Art When a semiconductor device is mounted on a substrate, a bonding wire is used to connect a bonding semiconductor element of the semiconductor device and a semiconductor element on the substrate. Recently, devices such as integrated circuit devices have become highly dense and have a large number of bonding parts. Under these conditions, the spacing between the bonding wires becomes very narrow, which can cause electrical shorts to occur due to contact between the bonding wires or contact between the bonding wires and the edges of the semiconductor device substrate. ing. To explain this in more detail, especially in a multi-bin integrated circuit device, as shown in FIGS. 1 and 2, the coated wire 1 to be connected is It becomes stiff or droopy. 3 is a substrate. In such a state, the bonding wire is likely to come into contact with the chip or other bonding wires, resulting in a short circuit. For this reason, generally, an inspection process is provided to manually correct the tension or sagging of the bonding wires as described above, or to discard those that cannot be corrected. However, doing so is extremely uneconomical, and improvements are required.

[Problems to be Solved by the Invention] In order to improve this uneconomical situation, the development of bonding equipment that can bond wires without causing tension or sagging as described above has been advanced, and a large amount of money has been spent. Although it requires cost, effort, and time,
The reality is that nothing satisfactory has yet been developed.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a heat-resistant polyurethane-coated bonding wire that will not cause a short circuit even if the wire is stretched or sagged.

[Means for solving problems]

In order to achieve the above object, the heat-resistant polyurethane-coated bonding wire of the present invention is such that the coating covering the outer periphery of the wire body is made by reacting a polyol component with an isocyanate, and the molecular skeleton contains a structural unit derived from terephthalic acid. It has a structure that includes.

[Function] That is, the present inventors changed their perspective from the development of the bonding device as described above, focused on the wire itself, and coated the wire itself to prevent short circuits even if tension or sagging occurs during bonding. I thought of doing it. We then used a commercially available urethane resin to cover the outer periphery of the wire body, anticipating that it would be possible to create a coating that would not cause cracks or peeling when the wire was bent, etc., and found that the commercially available product was not reliable enough. It became clear that such insulation could not be achieved. Therefore, as a result of further research, unlike commercially available urethane resins, we found that using heat-resistant polyurethane, which is made by reacting isocyanate with a polymer component whose main component is terephthalic acid polyol containing active hydrogen, provides reliable insulation. The inventors discovered that a film could be obtained and arrived at this invention. In particular, the insulating film made of heat-resistant polyurethane has the advantage that conventional bonding equipment can be used as is because the urethane bonds decompose and bonding is possible at the bonding temperature of ordinary bonding equipment. .

The film of the heat-resistant polyurethane-coated bonding wire of the present invention can be obtained using a polymer component whose main component is a terephthalic acid polyol containing active hydrogen and an isocyanate. Here, the term "main component" is intended to include cases where the entire component consists only of the main component.

The above-mentioned active hydrogen-containing terephthalic acid polyol is produced by using terephthalic acid and polyhydric alcohol to produce OH/C00H
= 1.2 to 30 and can be obtained by a conventional esterification reaction at a reaction temperature of 70 to 250°C. Generally, the average molecular weight is 300-10,000 and the hydroxyl group is 100-5o.

Those having hydroxyl groups at both ends of the molecular chain are used.

Raw materials constituting such terephthalic acid polyols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, hexane glycol, butane glycol, chrycerin, and trimethylolpropane.

Examples include fatty glycols such as hexanetriol and pentaerythritol. In addition, 1,4
- Polyhydric alcohols such as dimethylolbenzene. In particular, it is preferable to use ethylene glycol, propylene glycol, and glycerin.

As the dicarboxylic acid, terephthalic acid or its derivatives (dimethyl ester, etc.) are used, but amic acid and imide acid can be used in combination if necessary.

In addition, to the extent that the heat resistance does not decrease, we can also use two substances such as isophthalic acid, orthophthalic acid, succinic acid, adipic acid, and sebacic acid.
Basic acids, 1,2,3,4-butanetetracarboxylic acid,
There is no problem in using polybasic acids such as cyclopenkunetetracarboxylic acid, ethylenetetracarboxylic acid, pyromellitic acid, and trimellitic acid in combination. The proportion of the polybasic acid (including the acidic acid and imide acid) other than the above terephthalic acid (or its derivative) is usually equal to or less than the amount of terephthalic acid (or its derivative) used.

As the isocyanate to be reacted with the above-mentioned terephthalic acid polyol, the isocyanate group of a polyvalent isocyanate having at least two isocyanate groups in one molecule, such as toluylene diisocyanate and xylylene diisocyanate, is replaced with a compound having active hydrogen, such as phenol. Examples include those blocked with esters, caprolactam, and methyl ethyl ketone oxime. Such isocyanates are stabilized. Also included are those obtained by reacting the above polyvalent isocyanate compound with a polyhydric alcohol such as trimethylolpropane, hexanetriol, butanediol, and blocking the resulting product with a compound having active hydrogen.

Examples of the isocyanate compounds include Millionate MS-50, Coronae) 250, manufactured by Nippon Polyurethane Co., Ltd.
1.2503.2505. Coronet) AP-3t,
Desmoji: 2. - CT-3t, etc. The polyvalent isocyanate has a molecular weight of 3
It is preferable to use a number of about 00 to 10,000.

This invention insulates the wire body by preparing a coating composition using the above-mentioned raw materials and coating the wire body with the paint composition to form a film with a thickness of several μm.

The coating composition used in the present invention has 0.4 to 4.0 equivalents of isocyanate groups in the stabilized incyanate, preferably 0.9 to 2.0 equivalents, per 1 equivalent of hydroxyl groups in the polyol component.
It can be obtained by adding 0 equivalents and the required amount of a curing accelerating catalyst and further adding an appropriate amount of an organic solvent (phenols glycol ethers, naphtha, etc.) to make the solid content usually 10 to 30% by weight. . At this time, appropriate amounts of additives such as appearance improvers and dyes may be added as necessary. In this invention, the reason why 0.4 to 4.0 equivalents of isocyanate groups of the stabilizing isocyanate are added per 1 hydroxyl equivalent of the polyol component is that if the amount is less than 0.4 equivalents, the crazing properties of the resulting insulated wire will deteriorate;
On the other hand, if the amount exceeds 4.0 equivalents, the abrasion resistance of the coating film becomes poor. The curing accelerating catalyst added at the time of preparing the coating composition is preferably 0.1 to 10 parts by weight per 100 parts by weight of the polyol component. When this amount is less than 0.1 parts by weight, the curing accelerating effect tends to decrease and the ability to form a coating film tends to deteriorate.On the other hand, when it exceeds 10 parts by weight, the resulting heat-resistant urethane bonding wire has thermal deterioration characteristics. This is because a decrease in

Examples of the curing accelerating catalyst include metal carboxylic acids, amino acids, and phenols, specifically zinc salts, iron salts, copper salts, manganese salts, and cobalt salts such as naphthenic acid, octenoic acid, and versatic acid. , tin salt, 1,8-diazabicyclo(5°4.0) undecene-7,2,4,
6-) Lis(dimethylaminomethyl)phenol is used.

The heat-resistant polyurethane-coated bonding wire of the present invention can be obtained by applying the coating composition as described above onto the wire body and then baking it in a commonly used baking coating device.

The above coating and baking conditions vary depending on the blending amounts of the polyol component, stabilized isocyanate, polymerization initiator, and curing accelerating catalyst, but are usually 4 to 100℃ at 200 to 300℃.
It is about seconds. In short, baking is performed at a temperature and for a time sufficient to substantially complete the curing reaction of the coating composition.

The thus obtained heat-resistant polyurethane-coated bonding wire has an insulating coating made of heat-resistant polyurethane formed around the outer periphery of the wire body made of gold, aluminum, or copper. In this case, other insulating coatings may be used in combination to form a composite coating. This composite coating is obtained by forming the insulating coating of the present invention and then further forming another insulating coating on the insulating coating. In this case, it is preferable that the thickness of this insulating coating is set to be at most twice the thickness of the insulating coating of the present invention, preferably at most 0.5 times. Examples of the other materials for forming the insulation coating include polyamide resin, special polyester resin, and special epoxy resin.

〔Effect of the invention〕

As described above, in the heat-resistant polyurethane-coated bonding wire of the present invention, since the insulating film is composed of the heat-resistant polyurethane made of the above-mentioned special terephthalic acid polyol and isocyanate, the film may crack or peel due to bending or the like. Moreover, it has excellent heat resistance. Moreover, the insulating film does not generate carbides or the like and damage the wire bonding portion during thermal decomposition at high temperatures. Due to the effect of the insulating coating, even if the wire itself is stretched or sagged during mounting, no electrical short circuit will occur.

Next, examples will be described together with comparative examples.

〔Example〕

First, the raw materials shown in Table 1 are mixed in the proportions shown in the table, placed in a 500 cc flask, equipped with a thermometer and a steam condenser, and reacted to produce three types of terephthalic acid polyol P. -1, P-2, and P-3 were obtained. The ratio of terephthalic acid to ethylene glycol, reaction time, etc. at this time are also shown in Table 1. The end point of the above synthesis reaction is determined by the theoretical amount of reaction water and the acid number (
5 or less). In this case, a reduced pressure reaction was also carried out if necessary.

(Left below) Using the three types of terephthalic acid polyols P-1, P-2, and P-3 obtained as described above and a commercially available polyol, these polyol components and isocyanate components were added to the second A coating composition was prepared by blending the ingredients in the proportions shown in the table. The coating composition thus obtained was diluted to a concentration of 10% using a solvent, applied twice to the outer peripheral surface of the wire body, and then heated at 175°C for 21 minutes.
After-curing was performed at 170° C. for 2 hours to form an insulating coating made of heat-resistant polyurethane, and wire was manufactured. The composition and coating properties in this case are shown in Table 2 below.

(Left below) Next, a semiconductor element was mounted on a substrate using the heat-resistant polyurethane-coated bonding wire obtained as described above, and its performance was examined. The results are shown in Table 3 below.

(The following is a blank space) As is clear from Table 3 above, the semiconductor device using the heat-resistant polyurethane-coated bonding wire of the present invention has a small defective rate and no deterioration in reliability even after undergoing various tests. Further, the insulating coating made of the terephthalic acid polyol has improved heat resistance and can be directly bonded to a terminal or the like.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are explanatory diagrams of a conventional example. 1... Covered wire 2... Semiconductor element 3... Substrate 4... Terminal Patent applicant Hitachi, Ltd. Tanaka Electronics Co., Ltd. Nitto Electric Kogyo Co., Ltd.

Claims (1)

[Claims] (1) A heat-resistant polyurethane-coated bonding wire characterized in that the coating covering the outer periphery of the wire body is formed by reacting a polyol component with an isocyanate, and contains a structural unit derived from terephthalic acid in the molecular skeleton.