JPH04324601A - Carbon resin printing resistor paste - Google Patents

Abstract

PURPOSE:To harden carbon resin printing resistor paste at about 200 deg.C within a period of about 15 minutes. CONSTITUTION:This carbon resin printing resistor paste is prepared by mixing carbon with an epoxy-modified thermosetting polyimide resin and a multi- functional maleimide resin is used as the above-mentioned polyimide resin. In addition, a latent curing agent is mixed with the multi-functional maleimide resin.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed resistive paste, and more particularly to a printed resistive paste for use in printed resistors of thick film ICs.

0002

2. Description of the Related Art A conventional carbon printed resistor paste has a composition of 100% epoxy resin, 80% carbon, 30% inorganic filler, and 100% organic solvent. Epoxy resins are flexible and have good adhesion, making them suitable for screen printing, but they have the disadvantage of poor heat resistance and large fluctuations in resistance.

[0003] In order to improve heat resistance, we tried using polyimide resin instead of epoxy resin. There are two types of polyimide resins: Kapton type and Bismaleimide type. The Kapton type is a thermoplastic polyimide that dissolves only in highly polar solvents such as dimethylformamide and N-methylpyrrolidone, and the bismaleimide type is a thermosetting polyimide that can be dissolved in a wider variety of relatively weakly polar solvents. .

However, the Kapton type is extremely difficult to make into a paste, requires a strong polar solvent that is harmful to the printing stencil, and requires baking at a high temperature of 250°C or more for a long time, so it cannot be used with general phenol or epoxy. It cannot be used for system boards. The bismaleimide type is relatively easy to form into a paste with carbon, but like the Kapton type described above, it requires a strong polar solvent and baking at high temperature for a long time. Furthermore, due to brittleness and low adhesion, which are the drawbacks of the bismaleimide type, the biggest drawback is that not only can it not be uniformly screen printed with a film thickness of 20 μm or less, but also a structurally stable thick film resistor cannot be obtained. Ta.

[0005] Therefore, in order to solve the above problem, the applicant of the present invention solved the above problem by mixing carbon into an epoxy-modified thermosetting bismaleimide resin. Such a resistor paste has improved heat resistance and hot water resistance, and can form a stable printed resistor in a shorter time than before (see Japanese Patent Laid-Open No. 138304/1983).

[0006]

However, in the printing resistance paste based on the epoxy-modified thermosetting bismaleimide resin described above, since the bismaleimide resin is not polyfunctional, it cannot be easily modified with the epoxy resin.
As a result, there is a problem in that there are sufficiently modified parts and insufficiently modified parts in the entire printed resistor paste, resulting in variations in resistance values.

Another problem is that conventional printed resistor pastes have a high thixotropic ratio, making it difficult to perform screen printing.

[0008]

[Means for Solving the Problems] The present invention has been made in view of solving the above-mentioned problems, and consists of using a polyimide resin as a polyfunctional maleimide resin, and adding a latent curing agent to the polyfunctional maleimide resin. The above problem is solved by mixing.

[0009]

[Function] By making the printed resistance paste based on the epoxy-modified thermosetting polyfunctional maleimide resin, the maleimide resin and the epoxy resin can be easily modified. Furthermore, by incorporating a latent curing agent, the curing time by baking can be significantly shorter than that of conventional pastes.

0010

[Example] The carbon resin printed resistance paste according to the present invention contains 100% bisphenol or novolak epoxy resin, 5% to 30% maleimide polyimide resin, 0.5% to 10% latent hardening agent, 8% to 100% carbon, and 5% to 50% inorganic filler. 100, organic solvent in a weight ratio of 0 to 100.

A feature of the present invention is that the polyimide resin component of the epoxy-modified thermosetting polyimide resin is a polyfunctional polyimide (maleimide) resin. Since polyfunctional polyimide resin has many functional groups, it can be modified with epoxy resin very easily. On the other hand, another feature of the present invention is that a latent curing agent is mixed into the epoxy-modified thermosetting polyfunctional polyimide resin. A latent curing agent is a curing agent in a mixture of an epoxy resin and a curing agent that can be stored at a constant temperature for a long period of time without changing its properties and has the function of rapidly curing when heated to a predetermined temperature. In this embodiment, an imidazole-based curing agent, a dicyandiamide-based curing agent, or a tertiary amine-based curing agent is used.

The carbon resin printed resistor paste according to the present invention is fired after screen printing, and the paste of the present invention can form a stable printed resistor under firing conditions of about 200° C. for about 15 minutes. As a result, the baking time can be significantly shortened, whereas conventional bismaleimide resins are baked at about 180° C. in about 3 hours.

FIG. 1 is a characteristic diagram showing the resistance change characteristics of a resistor paste of the present invention and a conventional resistor paste at high temperature storage depending on the firing time. The measurement conditions were a resistance firing temperature of 200
The rate of change in resistance was measured at 150° C. for 15 minutes and at room temperature 150° C. for 1000 hours. FIG. 2 is a characteristic diagram showing the resistance change rate of the resistance paste of the present invention and the conventional resistance paste in a high temperature load test. As measurement conditions, resistance firing temperature 2
The rate of change in resistance was measured at 00°C for 1 hour and at room temperature 125°C for 1000 hours. In addition, in this measurement, the resistance firing time was
The reason for setting the time as 15 minutes as in FIG. 1 is because it is impossible to measure with conventional resistance paste. In both measurements, the printed resistor was formed on an aluminum substrate that had been subjected to insulation treatment.

In FIGS. 1 and 2, A is a conventional bisphenol-based epoxy resin-based carbon resin printed resistor paste, B is a conventional epoxy-modified thermosetting bismaleimide resin-based carbon resin printed resistor paste,
C1 is a carbon resin printed resistance paste based on a bisphenol-based epoxy-modified thermosetting polyfunctional maleimide resin of the present invention, and C2 is a carbon resin based on a novolac-based epoxy-modified thermosetting polyfunctional maleimide resin of the present invention. It is a printed resistance paste.

As is clear from FIGS. 1 and 2, the resistance change rate characteristics of the resistance pastes C and D of the present invention are significantly superior to those of the conventional resistance pastes A and B. The reason for this is that the polyfunctional maleimide resin has high heat resistance and hot water resistance so that the bond with carbon is maintained, and that a latent curing agent such as imidazole is used in the polyfunctional maleimide resin.

[0016] The resistance paste based on the epoxy-modified thermosetting polyfunctional maleimide resin of the present invention can be used with a relatively weakly polar ester-based solvent such as acetic acid diethylene glycol monobutyl ether, or a xylol-based single or mixed solvent. , it is possible to avoid fatal damage such as melting and swelling of printing stencils, and to perform screen printing.

[0017]

[Effects of the Invention] As detailed above, according to the present invention,
Since the carbon resin printed resistance paste is based on an epoxy-modified thermosetting polyfunctional maleimide resin mixed with a latent curing agent, it can be heated to about 200℃ for about 15 minutes compared to conventional carbon resin printed resistance pastes. It becomes possible to cure in an extremely short time, and the effectiveness of mass production of hybrid integrated circuits can be significantly improved.

Furthermore, since the carbon resin printed resistor paste of the present invention cures in a short time of 15 minutes as described above, it can be used even for resin-based substrates such as printed circuit boards. Furthermore, it has the advantages of polyimide resin, with high heat resistance and hot water resistance. Since the base polyimide resin is less likely to deteriorate, fluctuations in resistance can be minimized, making it possible to achieve highly accurate resistance.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the rate of change in high temperature storage resistance value depending on firing time.

FIG. 2 is a characteristic diagram showing the rate of change in resistance value due to a high temperature load test.

Claims (2)

[Claims] 1. A carbon resin printed resistance paste in which carbon is mixed into an epoxy-modified thermosetting polyimide resin, wherein the polyimide resin is a multifunctional maleimide resin, and a latent curing agent is mixed into the multifunctional maleimide resin. Carbon resin printed resistance paste. 2. The carbon resin printed resistance paste according to claim 1, wherein an imidazole hardening agent is used as the latent hardening agent.