JPS6348914B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a paint for electrical resistors for producing printed resistor elements formed on synthetic resin laminates. That is, the present invention relates to a mixed electrical resistance paint consisting of a resin and carbon, and particularly aims to provide a carbon-resin resistance paint used in the production of a hybrid IC based on an organic substrate. In recent years, so-called hybrid ICs that mount thick film circuits and semiconductors on the same substrate have become popular.
There has been a remarkable increase in Conventionally, most of the substrates used for this purpose are ceramics such as alumina substrates, and electrodes and resistors are formed on these substrates by printing and baking using a paste with glass as a binder, and semiconductors are mounted on top of these. is a common method. However, although ceramic-based HICs are highly reliable, they also have drawbacks such as the complicated manufacturing process due to the use of high temperatures in manufacturing, the inability to process them after circuit formation (for example, damage to holes, etc.), and the ease of breakage. In this field as well, studies have been made on the production of HICs using organic substrates. This method involves forming circuit electrodes by etching a copper-clad laminate, forming a resistor between the electrodes by printing, and then mounting a semiconductor on the electrodes. However, the fundamental reason why this method has not reached the stage of practical application is that the resistance value stability of the carbon resistance paint is poor. In other words, the HIC manufacturing process involves many heat-intensive processes (soldering, powder coating, etc.), which causes the problem that the initially adjusted resistance value changes. It was also necessary to meet performance requirements such as no change in resistance even under such severe moist heat treatment, and the idea of creating an organic substrate HIC using an organic binder resistance paint was no longer possible. It was thought to be close. In view of these current circumstances, the inventors of the present application have conducted intensive studies to somehow develop a carbon resistance paint for HIC on organic substrates, and have finally arrived at the present invention. Of course, if a paint that can cover the resistance of HIC can be obtained, it goes without saying that it is also excellent as a general resistance paint. That is, we have discovered that only a resistance paint in which carbon black and/or graphite powder is dispersed in a mixture of phenolic resin and oil-soluble melamine resin using an appropriate solvent satisfies the above performance. This invention has significance. In making the present invention, the present inventors discovered the following phenomenon, and the present invention skillfully utilizes this phenomenon. In other words, as a result of considering the difficult problem of PCT performance, in the case of using phenolic resin alone,
We have discovered that while PCT treatment causes the resistance value to drift in the positive direction, when the paint is prepared using only oil-soluble melamine resin, the PCT treatment causes the resistance value to drift in the negative direction. It has also been found that a mixture of the two exhibits a value intermediate between the two, and that by appropriately adjusting the mixing ratio, a resistance paint with an infinitely close to zero change can be obtained. The reason for this is not clear, but it is an interesting fact, and it has made it possible to obtain HIC resistance paints, which was previously considered impossible. The details of the present invention will be described below. As the resol-type phenolic resin used in the present invention, all resols such as phenol resol, alkyl phenol resol, and xylene resin-modified phenol resol can be used, but generally, ammonia-catalyzed phenol resol is used. On the other hand, oil-soluble melamine resin is used to achieve the present invention from the viewpoint of moisture resistance and high crosslink density. Furthermore, since the oil-soluble melamine resin is required to have good compatibility with phenol resol, it is generally preferable to use butyl etherified melamine. Both resins are then mixed. The mixing ratio should be based on experimentation so that the resistance value changes as little as possible in the PCT test, but in general, the negative side for oil-soluble melamine resin alone is higher than the positive drift for phenolic resin alone. The amount of oil-soluble melamine resin added is small compared to the amount of phenolic resin, since the drift to phenol resin is large. The ratio of phenolic resin to oil-soluble melamine resin is preferably in the range of 10:1 to 10:10 (by weight). If the ratio of the oil-soluble melamine resin is smaller than 10:1, the contribution of the oil-soluble melamine to the negative side will be small, and if it is 10:10 or more, it will drift to the negative side. Further, as the carbon used, all general conductive carbons can be used, and carbon blacks with a developed chain structure such as acetylene black, or graphites can be used alone or in combination. In particular, it is preferable to use both in combination in order to stabilize the resistance value. Further, the amount of carbon added can be adjusted as appropriate depending on the desired resistance value. As mentioned above, resin and carbon are mixed, but usually a solvent is used to adjust the viscosity and printability.In this case, it is necessary that the solvent does not volatilize during printing, so a solvent with a slow volatilization rate is preferably used. It will be done. Generally, solvents such as butyl carbitol, butyl carbitol acetate, butanol, and benzyl alcohol are used alone or in combination, but any solvent can be used as long as it is a good solvent for both resins. A mixture containing these resins, carbon, and a solvent as main components is kneaded to obtain a carbon paste, and a ball mill, three-ink roll, or the like is used for kneading. Next, a carbon paste whose resistance value has been appropriately adjusted is printed between the electrodes of the copper foil circuit board and fired.
A range of 0.degree. C. to 200.degree. C. is used. Of course, this temperature must be set in relation to the heat resistance of the organic substrate. Therefore, an organic substrate that can be fired at a high temperature is preferable from the viewpoint of resistance value stability, and polyimide copper-clad boards and heat-resistant epoxy resin copper-clad boards are generally preferred. Next, the formed resistor and circuit are coated with a resist, leaving the terminal portion and the semiconductor mount portion (electrode portion), and then heated and cured. Thereafter, the resistance of the resistor is adjusted to a desired resistance value by trimming. As a result, a HIC circuit board with a resistor is obtained. This state corresponds to a conventional ceramic circuit board with a resistor. Furthermore, if necessary, only the terminal portions, electrode portions, and stitch portions may be plated with gold. Next, the IC is mounted on the tower and gold wire bonding is performed, and then only the gold wire bonded IC portion is sealed using chip coat resin (generally silicone resin), which is also heated and cured. Next, the chip parts are mounted using solder as necessary, then leads are attached to the terminals using solder, and as the final step, the exterior is applied with epoxy resin powder paint.
In this way, HIC with legs can be obtained. In this way, the printed carbon resistor is exposed to heat until the final product is obtained, resulting in deviation from the initial resistance value after trimming, that is, drift. Representative examples of the temperature and time of this thermal step are as follows. Mounting of chip parts 150℃ 0.5 hours Gold wire bonding 150℃ several minutes Heat curing of chip coat resin 100℃ 3 hours Soldering terminal leads 220℃ several seconds Heat curing of exterior powder resin 150℃ 2 hours or more After going through such a heat process 3 for the initial value even after
% stability is required. Lastly, there is a pressure resistance test (conditions: 125°C, 2.3 atm) as a reliability test of resistance value, which requires performance such that the change after 50 hours of treatment is within 3%. It was thought that a carbon resistance paint using an organic resin as a binder that would satisfy all of these very strict performance requirements would be impossible. However, the present inventors found that in the case of a phenolic resin binder alone and in the case of an oil-soluble melamine resin binder alone, the change in resistance value due to heat and moist heat has a positive and negative relationship, and when the two are mixed, they cancel each other out. The present invention was achieved by discovering a completely unthinkable phenomenon in which the change in resistance value approaches zero without limit. Examples will be described below. Example 1 Resol type phenolic resin (Sumilite Resin
PR-51833, manufactured by Sumitomo Durez Co., Ltd.) 50 parts by weight butyl etherified melamine resin (Super Betsukamine L-117-70B, manufactured by Dainippon Ink Co., Ltd.)
40 parts by weight catalyst (Catanit P, manufactured by Nitto Chemical) 4 parts by weight Carbon black (acetylene black)
22 parts by weight of solvent and 10 parts by weight were weighed out and stirred and mixed for 20 minutes using three ink kneading rolls to prepare a paste-like carbon resistance paint. Next, this paste was applied by screen printing onto a previously prepared circuit pattern (glass epoxy board), dried at 120℃ for 20 minutes, and after the solder resist was printed and cured, it was heated and cured at 150℃ for 4 hours. A circuit board with a resistor was created. The resistance value of the printed resistor obtained in this way is 2.19K
It was Ω/□. Next, the processes necessary for hybrid IC assembly, namely curing of adhesive for die bonding, curing of adhesive for bonding, curing of resin for chip coating,
The resistor circuit board was heated under conditions equivalent to curing adhesive for mounting chip components to give it a thermal history, and then soldered and coated with powder to form a resistor network. At this time, the resistance value of the printed resistor is 2.14K
Ω/□, -2.28 compared to before adding thermal history
% change. Next, this test piece was heated to 125°C for 2.3
After being left in a high temperature and humid environment at atmospheric pressure for 32 hours, the resistance value was measured to be 2.18KΩ/□, which was a slight change in resistance value of +1.87% compared to before the pressurization. It showed excellent resistance value stability. Example 2 Resol type phenolic resin 50 parts by weight Butyl etherified melamine resin 20 〃 Catalyst 2 〃 Carbon black 10 〃 Graphite 7 〃 Solvent 16 〃 Using the paste of the above formulation, the method shown in Example 1 was carried out completely. Similarly, a circuit board with a resistor was created. The resistance value of the obtained printed resistor was 34.2KΩ/
It was □. Next, the thermal history was added in the same manner as in Example 1, and the rate of change in resistance was measured -1.90
%, and the rate of change in resistance value after 32 hours of PCT (125°C, 2.3 atm) was +2.14% compared to before the pressure vacuum treatment, indicating excellent resistance value stability. Comparative example (formulation 1) Resol type phenolic resin (PR-51833)
100 parts by weight Carbon black 18 Graphite 6 Solvent 10 (Formulation 2) Butyl etherified melamine resin (L-117-70B)
100 parts by weight catalyst (Catanite P) 11 〃 Carbon black (Furness black)
21 〃 Solvent 16 〃 The resistance value stability of Formulation Examples 1 and 2 was evaluated in exactly the same manner as in the examples, and the results are as shown in Table 1. value

[Table] changed, and it could not withstand use as a resistor circuit board that requires high reliability, that is, a high degree of resistance value stability.

Claims (1)

[Claims] 1. A resol-type phenolic resin obtained by an ammonia catalyst method and an oil-soluble melamine resin are mixed in a mixed varnish in which the mixing ratio of resol-type phenolic resin:oil-soluble melamine resin is in the range of 10:1 to 10:10. , carbon black and/or graphite fine powder dispersed therein using a solvent.