JPH0416941B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to the construction of a wiring board in which electronic components and semiconductor elements are melt-bonded by soldering to a wiring board containing a substance with a low heat resistance temperature. A film made of a material with lower thermal conductivity is formed.

[Prior art]

Hybrid modules in which electronic components and semiconductor elements are bonded to a wiring board by soldering are already widely known. Many of these modules use alumina ceramic, which has good heat resistance, for the substrate, and a circuit pattern is directly formed on the ceramic substrate, and components are soldered to the desired positions of the circuit pattern.

In some modules, a glass material having poor thermal shock resistance is used for the substrate, and the module is formed with the same structure as the ceramic substrate. However, after mounting materials or components with low heat resistance on these modules, it is necessary to solder the electronic components and semiconductor elements, and soldering is performed by locally heating only the soldering points. In this case, the heat generated by local heating causes a large temperature gradient in the planar direction of the substrate, causing a problem that the substrate may break.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for configuring a wiring board that eliminates the above-mentioned drawbacks and does not cause damage to the board even when subjected to local heating.

[Summary of the invention]

In the present invention, a film made of a material with lower thermal conductivity than the substrate is formed on the substrate, a wiring pattern is formed on the upper surface of the film, and electronic components and semiconductor elements are soldered onto the wiring pattern by local heating. It has been made possible.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 shows a liquid crystal module 8 in which a liquid crystal 6 is sealed between a lower glass substrate 2 and an upper glass substrate 4.
A semiconductor element 10 for driving a liquid crystal is connected to the upper surface of the lower glass substrate 2.

FIG. 2 is an enlarged cross-sectional view of a part of FIG. 1, and the same reference numerals as in FIG. 1 indicate the same contents. In FIG. 2, lower substrate 2 and semiconductor element 10 are connected by solder 12. In FIG. The third step was to enlarge the semiconductor element junction of the conventional configuration.
As shown in the figure. In this figure as well, the same reference numerals as in FIGS. 1 and 2 indicate the same contents. In FIG. 3, a semiconductor element 10 is soldered to a bonding area of a wiring pattern 14 formed on a glass substrate using a solder 12. In this case, in order to prevent the solder from spreading on the wiring pattern 14, the solder mask 16 is used so that only a certain area on the wiring pattern is wetted with the solder, and other parts are covered.

FIG. 4 is a diagram showing the structure of a substrate according to the present invention, and the same reference numerals as those in the previous figures indicate the same contents. In FIG. 4, on the glass substrate 2,
A film 20 made of polyimide resin is formed. FIG. 5 explains the method of soldering the module according to the present invention, in which the liquid crystal module 8 is installed in a tunnel furnace 22 whose atmosphere can be controlled, and the preheating plate 24 is placed at the bottom of the tunnel furnace 22. You can preheat the module from below. The upper surface of the tunnel furnace 22 is sealed with a lid 28 through which heat rays emitted from an infrared lamp 26 are transmitted.

First, as shown in FIG. 4, a film 20 made of polyimide resin is formed on a glass substrate 2 by a printing method at a position where a semiconductor element 10 is to be installed. After forming the film 20, chromium, copper, and chromium are deposited on the glass substrate 2 by vapor deposition to form the wiring pattern 14. Thereafter, a photo process and an etching process are carried out to form a wiring pattern, and the wiring pattern 14 necessary for the module is formed. The solder mask 16 has a three-layer structure of chromium, copper, and chromium, and the top layer of chromium is removed by etching in the form of a window to expose the copper in the lower pattern portion 14 so that only the copper can be soldered. I have to. The semiconductor element 10 is soldered with solder 1 in advance.
The soldering pattern of the substrate 2 and the solder 12 of the semiconductor element 10 are aligned and temporarily connected. In this state, the wiring pattern 14 and the solder are only in contact and are not completely joined. Next, the temporarily aligned module 8 is placed in a tunnel furnace 22 replaced with _N2 gas, as shown in FIG. Here, module 8 is heated approximately by the preheating plate.
Preheated to 100℃. At the same time, the semiconductor element 10 is soldered to the center of the infrared lamp 26.
move it to the top surface. The second focus of the infrared lamp 26 is focused on the upper surface of the semiconductor element 10, and lighting of the infrared lamp 26 causes the semiconductor element 1 to
The upper surface of the solder 1 is heated, and the heat on the upper surface of the semiconductor element 10 is conducted inside the element 10 shown in FIG.
2 to reach the membrane 20. Here, semiconductor element 1
0 and the solder have high thermal conductivity, so the temperature rises rapidly. However, since polyimide resin with low thermal conductivity is used for the film 20, heat transfer is suppressed by the film 20, and the temperature rises rapidly at the bottom of the film 20. It is possible to suppress the temperature rise of certain glasses. Furthermore, by suppressing this heat transfer, the temperature of the solder 12 is accelerated. In this way, the solder 10 is heated and melted, and the wiring pattern 14
and the semiconductor element 12 are soldered together.

The infrared rays emitted from the infrared lamp 26 may pass through the outer periphery of the semiconductor element 10 and directly irradiate the substrate 2. In such a situation,
If the polyimide resin is directly irradiated with infrared light, the resin will generate a large amount of heat, and the glass 2 will be damaged due to heat transfer from the generated resin to the glass 2. For this reason, the film 20 is provided only under the semiconductor element 10, so that the polyimide resin is not directly irradiated with infrared light.

In this embodiment, polyimide resin is used as a material whose thermal conductivity is smaller than that of the substrate, but materials other than polyimide resin are naturally included as long as they meet the above purpose. Furthermore, although an infrared lamp is used as a heating method, it is also fully applicable to a case where a laser beam is used, a heating block, and a local heating method using a heated gas.

Although the film 20 was formed on the substrate 2 by a printing method, a dipping method, a spinner (rotary coating), or the like may also be used.

〔Effect of the invention〕

According to the present invention, the small thermal conductor film suppresses heat transfer to the substrate in response to heating from the semiconductor element side, so the temperature gradient of the substrate can be reduced and damage to the substrate can be prevented. Furthermore, the suppressing effect can improve the temperature rise speed of the soldered part, shorten the soldering time, and reduce the thermal influence on components with low heat resistance.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a liquid crystal module, FIG. 2 is a cross-sectional view of the liquid crystal module, FIG. 3 is a cross-sectional view of a conventional semiconductor element mounting part, and FIG. 4 is a semiconductor element mounting part of an embodiment of the present invention. 5th cross-sectional view of
The figure is a sectional view showing a method for attaching a semiconductor element. 2...Glass substrate, 8...Liquid crystal module, 1
0... Semiconductor element, 12... Solder, 14... Wiring pattern, 20... Film, 22... Tunnel furnace,
26...Infrared lamp.

Claims (1)

[Claims] 1. A glass substrate, a film provided on the glass substrate and having a thermal conductivity lower than that of the glass substrate, a wiring pattern provided on the film, and a solder melt connected to the wiring pattern. A semiconductor module comprising a joint portion and a semiconductor element provided on the solder fusion joint portion.