JPS63261790A - Hybrid integrated circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hybrid integrated circuit board in which terminals for solder connection of components are formed with a thick film conductor mainly composed of silver, and particularly relates to a hybrid integrated circuit board in which terminals for solder connection of components are formed with a thick film conductor mainly composed of silver. [Prior art] In hybrid integrated circuits, individual components such as ICs and LSIs, package elements such as chip capacitors, resistor chips, clip leads for external input/output, etc. are soldered with Pb-Sn solder paste 70 It is connected to the terminal on the board by - or dip.

Next, a conventional terminal structure will be explained using FIGS. 5 and 4. In the figure, terminal 2 is alumina.

It is formed by film printing technology on an insulating substrate 1 made of glass ceramic or the like along with circuit wiring 5 and a resistor (not shown), and usually the resistor is coated with a glass film for mechanical protection and to improve environmental resistance. 4. On the other hand, regarding the terminals, in order to prevent bridge short circuits between the terminals of the terminal row for multi-pin elements and the input/output terminal row due to solder, a glass film 4 is separated from the terminal 2 between the terminals as shown in the figure. It is formed in a state where In most cases, the conductive material for the terminals and wiring mentioned above is Ag-Pd based mainly on silver.

Ag-Pt based materials are used. A related literature includes, for example, "Thick Film Multilayer Circuit Board; Electronic Materials, May 1985, pp. 54-59."

In order to improve the solder connection strength of components on hybrid integrated circuit boards, various improvements have been made to terminal conductor materials, solder materials, solder connection shapes, etc., but in particular, the decline in connection strength over time is basically This is because Sn in the Pb-8n solder diffuses into the terminal film during soldering and the subsequent thermal history, forming an Ag s Sn alloy. When Srl diffusion reaches the terminal-substrate interface, , it is said that the connection strength decreases significantly. A related literature includes, for example, "Analysis of adhesive strength deterioration of rAg/Pt metallization; Proceedings of the 1st Microelectronics Symposium, July 1985, pp. 61-63".

[Problem that the invention seeks to solve]

The conventional hybrid multiplication circuit board described above has a problem in that the connection strength of the components soldered to the terminals decreases in a short period of time due to being left at high temperatures or through temperature cycling, resulting in poor reliability of component connections.

When parts are connected using Pb-8n solder to an Ag-based terminal film, it is inevitable that the connection strength will decrease over time due to the reasons mentioned above. Since the time taken for Sn to completely diffuse in the direction l is shorter, the present inventors have found that one of the causes of the decrease in connection strength is En diffusion from the outer peripheral side surface of the terminal. This is due to the structure of the terminal film. That is, in the conventional terminal structure shown in FIGS. 3 and 4, solder adheres not only to the upper surface of the terminal but also to the outer peripheral side surface thereof. Therefore, during soldering, Sn that has already diffused from the 91st surface is present at the terminal-substrate interface at the bottom of the outer peripheral side surface.
As a result, an Ag5in alloy is formed, and a portion with low connection strength is created at the terminal-substrate interface. And S under high temperature environment
Due to accelerated diffusion of n and stress concentration due to thermal expansion differences between the board, terminal film, and solder during the heating cycle, the terminal film peels off from the areas with low connection strength, reducing the connection strength of the solder connection terminal. 9, which is considered to cause a rapid decline.
The object of the present invention is to prevent the Sn diffusion from the outer peripheral side of the A (type terminal film) described above, thereby increasing the connection strength at the terminal-to-substrate interface, and providing a hybrid integrated circuit with a terminal structure that provides highly reliable component connection. Our goal is to provide circuit boards.

[Means for solving problems]

The above object is achieved by covering the outer periphery of the terminal with a glass film in a hybrid integrated circuit board in which terminals for solder connection of components are formed with a thick film conductor mainly composed of silver.

[Effect]

In the hybrid integrated circuit board of the present invention configured as described above, the solder for connecting the terminals and the components adheres only to the upper surface of the terminal, which is not covered by the glass film. Therefore, since Sn in the solder diffuses only from the upper surface of the terminal film, there is no formation of Ag3Sn alloy at the interface that reduces the connection strength of the terminal-substrate interface during solder bonding.
・In addition, with this terminal structure, the outer periphery of the terminal is sandwiched and pressed between the glass film and the board, which increases the resistance to peeling off the terminal film, and these combine to reduce the connection strength of the soldered terminal. K can be improved.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In the first case and FIG. 2, on the alumina sintered substrate 1, A
A g-Pd based conductive paste is applied using a well-known thick film printing technique, dried at 120°C, and then fired at 8500C for 10 minutes to form a terminal 2 with a film thickness of 10 μm and a size of 1.5 m x 1. Circuit wiring 3 was formed. After forming thick film crossovers and thick film resistors (not shown) according to the circuit configuration by printing and firing, an aluminoborosilicate glass paste that forms a glass film is fired at 550'C for 10 minutes. Thick film wiring 3. The outer edge of the terminal 2 was printed and fired together with the thick film resistor, and the thick film was covered with the glass film 4. Regarding the terminal, leave an exposed area of 1.5-, +G40 on the upper surface for solder connection, and assume that the outer periphery is sandwiched between the glass film 4 and the substrate 1. It also serves to improve the performance and prevent solder bridging between terminals in the input/output terminal row. This terminal 21 external input/output clip lead was humidified and Pb containing 2% Ag was used.
Connections were made by dipping in a -8N eutectic solder bath at 250°C for 5 seconds.

The solder connection strength was measured by the Beer method, in which the lead portion of the clip lead was bent perpendicularly to the board and then peeled off. The decline in connection strength over time was measured after the soldered clip leads were left for 150'C1000 hours.

In addition, in the conventional example for comparison, the film thickness is 10 μm.

A terminal was formed in an area of 1.5 m4, and the glass film was configured to cover the wiring part of the terminal and the substrate surface between the terminals as shown in FIGS. 3 and 4. Measurement of solder connection and connection strength was carried out in the same manner as in the examples of the present invention.

Table 1 shows the initial connection strength and 1500 of the embodiment and conventional example.
C- Comparison of connection strength over time after 1000 hours ○ As is clear from the first cover, ζ According to the embodiment of the present invention, the area of the solder joint is smaller than that of the conventional example 0 of
．． 75 times), the initial connection strength was 1°55 times as strong. Furthermore, the connection strength over time after 1000 hours at 150°C was 167 times higher than that of the conventional terminal structure. The material and the method for forming the terminal film are not limited to the embodiments, and the substrate material may be alumina, various glass ceramics, mullite/AlN, SiC, etc., and the substrate may be sintered. It may be a green sheet instead of a body. Furthermore, the present invention is not limited to cases in which the terminal film is directly formed on these substrates, but also in cases where an insulating film such as a so-called glass material is interposed between the layers of the substrate and the terminal.

〔Effect of the invention〕

According to the present invention, in a hybrid integrated circuit board in which terminals are formed with a thick film conductor mainly composed of silver, it is possible to increase the strength against peeling off of the outer peripheral portion of the terminal film, which has a large effect on the solder connection strength of components. This has the effect of further improving the reliability of component connections. Moreover, the present invention can be easily implemented without adding any special materials or processes by covering the outer periphery of the terminal film using the covering glass film on the substrate.

[Brief explanation of drawings]

FIG. 1 is a plan view of a terminal section showing one embodiment of the present invention, and FIG.
The figures are a cross-sectional view taken along the line A-A' in FIG. 1, FIG. 3 is a plan view of a terminal portion showing a conventional example, and FIG. 4 is a cross-sectional view taken along the line B-B' in FIG. Explanation of symbols 1... Board 2... Terminal 6... Circuit wiring 4... Covered glass membrane agent Patent attorney Small
Katsuo Kawa (6 (J, "'

Claims (1)

[Claims] 1. A hybrid integrated circuit board in which terminals for solder connection of components are formed with a thick film conductor mainly composed of silver, characterized in that the outer periphery of the terminal is covered with a glass film.