JPH0787262B2 - Method for forming resistor in hybrid integrated circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming a resistor in a hybrid integrated circuit, and more specifically, a technique for improving the high temperature storage characteristic of the resistance value of a thick film resistor. Regarding

[Background technology]

Conventionally, a thick film resistor was formed by printing a resistance paste such as a carbon resistance paste between Ag electrodes on a resin substrate and repeating the step of drying and then curing each resistance paste. . Then, after manufacturing the wiring board,
A component is mounted on this wiring board, soldering is performed by a method such as solder dipping, and the component is mounted on the wiring board to manufacture a hybrid integrated circuit.

[Problems to be Solved by the Invention]

As described above, the components are mounted on the wiring board by solder dip, etc., but due to the rapid thermal stress due to the solder dip etc. when mounting this component, the thick film resistor has the following characteristics as a characteristic after hardening. Internal stress and strain occur. Therefore, the resistance change rate of the thick film resistor when left at high temperature is considerably deteriorated as compared with the case where the solder dip is not performed.

As a countermeasure for this, there is a method of relaxing the internal stress of the thick film resistor by thermal aging after solder dipping. However, this method requires treatment at 150 ° C for 3 hours at a fairly high temperature and for a long time,
Considering the heat resistance of the resin substrate, this process may cause deterioration in general resin substrates, and since it is a process performed after component mounting, components with low heat resistance (for example, the heat resistant temperature of an electrolytic capacitor is , Usually 85 ° C.), This method cannot be used.

Therefore, the present invention has been made for the purpose of providing a method for improving the high temperature storage characteristics of a thick film resistor without the above-mentioned drawbacks.

[Means for Solving the Problems]

A method for forming a resistor of a hybrid integrated circuit according to the present invention includes a step of printing a resistor paste on a surface of a substrate and drying the paste to form a plurality of layers, and then forming an initial state of each resistor of a plurality of layers having different thermal histories. It is characterized in that a low-temperature heat treatment for a short time is performed for alignment, and immediately after that, the resistors are cured.

[Action]

Immediately before curing the resistance paste, in the present invention, the resistance paste was printed on the substrate and dried, and then, in the conventional method, the resistance paste was immediately cured to form a thick film resistor. In addition, by applying a short-time low-temperature heat treatment (drying temperature or more) to align the initial state of each resistor of multiple layers with different thermal history, it is possible to improve the high temperature storage characteristics of the resistance value of the thick film resistor. It was That is, the initial state of the resistance paste can be made uniform by applying heat treatment immediately before the curing process of the resistance paste, thereby forming a thick film resistor having uniform and stable characteristics and changing its resistance value with time. Can be reduced.

Further, since the heat treatment in this method is a treatment before hardening of the thick film resistor, that is, a treatment before mounting the components, it is carried out without affecting the mounted components and without being restricted by the type of components used. be able to. Furthermore, since the heat treatment in this method can be completed in a short time (several minutes to several tens of minutes),
It does not significantly affect the total process time of the hybrid integrated circuit, and the manufacturing efficiency is hardly reduced.

Further, since the heat treatment in this method can be performed at a temperature close to the drying temperature (a lower temperature is more effective) in a short time, even if the substrate is a resin substrate, there is no fear of heat deteriorating the substrate. .

〔Example〕

 Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Since the manufacturing process of the hybrid integrated circuit as shown in FIG. 2 having the thick film resistor on the surface of the substrate is shown in FIG.
A description will be given below along the flow of FIG.

In the embodiment, the substrate 1 is a resin substrate such as an epoxy resin substrate or a phenol resin substrate. An Ag electrode 3 having a predetermined wiring pattern is formed on the surface of the substrate 1, and thereafter, a resistance paste 2a, 2b, ... Such as a carbon resistance paste is printed on the substrate 1 by a method such as screen printing and dried. To be The resistance pastes 2a, 2b, ... Are repeatedly printed at predetermined positions on the substrate 1 each time the sheet resistance value differs, and dried. After the printing and drying of several types of resistance pastes 2a, 2b, ... Having different sheet resistance values are completed in this way, the substrate 1 is sent to the heat treatment step, and the resistance paste 2
Short heat treatment is applied to a, 2b, .... Here, the heat treatment is performed at a temperature higher than the drying temperature (> 60 ° C.), but a lower temperature is effective in improving the high temperature storage property. Further, the heat treatment time is several minutes to several tens minutes, but 10 to 20 minutes is suitable. Immediately after the heat treatment is completed, the resistance pastes 2a, 2b, ... Are hardened to form thick film resistors 4 such as carbon resistors on the surface of the substrate 1.
Further, the substrate 1 is subjected to required processing to manufacture a wiring substrate. In this way, mounting components are mounted on the manufactured wiring board and soldered by a method such as solder dipping.

The above heat treatment is performed in order to align the initial state so that no characteristic difference occurs between the thick film resistors after curing by performing the heat treatment immediately before the process of curing the thick film resistor, Especially, the initial state can be made uniform so that the characteristic difference does not occur depending on the number of times the resistance paste is dried. Therefore,
A thick film resistor with uniform and stable characteristics is formed during the curing process, and also during the solder dipping process.
The generation of internal stress and internal strain can be suppressed. For this reason, when the thick film resistor is left at high temperature, the change in resistance value over time becomes small, and the high temperature storage property is improved.

(Measurement results) The values shown in Fig. 3 are at 70 ℃, 100 ℃ and 170 ℃.
This is the result of measuring the rate of change of resistance value after leaving the thick film resistor that has been heat-treated for 20 minutes at the ambient temperature of 85 ° C for 72 hours, and the rate of change (%) is shown on the vertical axis. There is no particular meaning on the horizontal axis. It can be seen from this graph that the lower the heat treatment temperature, the higher the degree of improvement in the high temperature storage characteristics, so it is clear that the high temperature storage characteristics can be improved satisfactorily by performing the heat treatment near the lowest temperature at which the resistance paste can be dried. is there.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, the high temperature standing characteristic of a thick film resistor can be improved by the low temperature heat treatment for a short time before hardening, and the stable thick film with little change with time of the resistance value of a thick film resistor at high temperature. A resistor can be obtained. Moreover, since the heat treatment is performed before mounting the components, the mounted components having a low heat resistant temperature are not deteriorated, and the components can be applied over a wide range without being limited by the type of the mounted components. Furthermore, since heat treatment for a short time is sufficient, it does not significantly affect the total process time of the hybrid integrated circuit. Further, since heat treatment at a relatively low temperature for a short time is sufficient, deterioration of the substrate does not occur even in the case of a resin substrate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process drawing showing an embodiment of the present invention, FIG. 2 is a plan view showing a thick film resistor formed on a substrate of the same, and FIG.
The figure is a graph showing the high temperature storage characteristics of the change rate of the resistance value of the thick film resistor. 1 ... Substrate 2a, 2b ... Resistor paste

Claims (1)

[Claims] 1. A low-temperature heat treatment for a short time for aligning the initial state of each resistor of a plurality of layers having different thermal histories after repeating a step of printing a resistance paste on a surface of a substrate and drying it to form a plurality of layers. The method for forming a resistor in a hybrid integrated circuit, comprising: