JPH0266991A - Surface mounting ceramic substrate - Google Patents

Abstract

PURPOSE:To decrease the temperature difference between components as far as possible and to prevent excessive heating by providing a black overglaze part around a part whose radiated energy absorbing rate is low on a ceramic circuit substrate. CONSTITUTION:A black overglaze part 7 is provided around the mounting part of a white ceramic chip carrier 4. Thus, the energy absorbing rate of infrared rays is improved. In this way, temperature difference between the part 7 and a QFP 3 is eliminated by the radiated heat from the components and heat conduction from the black overglaze part 7. Solderging can be performed at the uniform temperature. A highly reliable double-mounting type substrate can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ceramic circuit board on which surface-mounted components are mounted.

(Prior art and its problems) A method of soldering surface mount components to a ceramic circuit board is to apply cream solder to the round part of the ceramic circuit board, which corresponds to the electrode part of components such as ICs and transistors mounted on the ceramic circuit board. The most common method is to print the parts, mount them, heat them with an infrared conveyor that uses radiation heating, and melt the solder to connect them.

Conventionally, QF P (Quad F lat
When mounting components with a large radiated area, such as a chip carrier with a white ceramic envelope, the near-infrared rays used to heat parts of the solder reflow have a high radiant energy density, and energy absorption due to color Since the QFP package has a higher energy absorption rate than a ceramic circuit board or a component with a ceramic envelope, the temperature rises faster than other components. On the other hand, since white ceramic parts have extremely poor radiant energy absorption rate, there is a temperature difference between the QFP and the part whose envelope is made of white ceramic, resulting in a difference in the solder melting time of the mounted parts. For this reason, the QFP becomes excessively heated, resulting in large residual strain due to the difference in thermal expansion between the resin mold and the ceramic circuit board, and when thermal history is applied, problems such as peeling of the bonded portion may occur.

FIG. 2 shows a cross-sectional view of a conventional double-sided mounting ceramic substrate. Rounds (2) and (5) for soldering circuits and components are printed and fired using a thick film on the ceramic substrate (1), and then an overglaze (
6) is printed and fired. Cream solder is printed on the board, QFP (3), a chip carrier (4) with a white ceramic envelope, and other parts are mounted, and the cream solder is melted by infrared radiant heating in an infrared heating conveyor furnace. soldering.

In this case, heating is done by radiation, and since the radiant energy absorption rate varies greatly depending on the material, surface condition, hue, etc., the heating state differs from case to case. The epoxy resin that packages the active elements is black and the main surface is matte, making it a white ceramic chip carrier (4).
The temperature rises faster than that, resulting in overheating. For this reason, excessive thermal strain is applied to the active elements in the mold, and thermal expansion strain between the substrate and the mold resin becomes larger, and residual strain occurs in the solder joint, causing a decrease in reliability.

(Means for Solving the Problems) In order to solve these drawbacks, the present invention provides a black overcraze portion around the parts of the ceramic circuit board that have a low radiant energy absorption rate, thereby reducing the amount of radiation emitted from the infrared heating section. QFP efficiently absorbs all the wavelengths
To provide a board that reduces the temperature difference between parts as much as possible to prevent excessive heating by making the energy almost equal to that absorbed by a black resin mold such as, and has a highly reliable solder joint state with little thermal distortion. It is in.

This will be explained in detail below with reference to the drawings.

(Example) Figure 1 shows a cross section of a white ceramic chip carrier (4) according to the present invention, with a black overglaze (
7) and improves the infrared energy absorption rate, the radiant heat of the component and the heat conduction from the black overglaze part eliminates the temperature difference with Q F P (3) and allows soldering at a uniform temperature. This makes it possible to provide a highly reliable double-sided mounting board.

(Effect of the invention) As described above, in the present invention, the black overglaze portion is provided around the parts with low energy absorption rate.
Since the heat absorption rate is almost equal to the energy absorbed by black resin molds such as FP, it is possible to reduce the temperature difference between parts, eliminate the difference in thermal expansion between the resin mold and the ceramic circuit board, and prevent peeling of the joint part. Therefore, it is possible to provide a highly reliable board.

[Brief explanation of the drawing]

1...Ceramics board, 2...Soldering round,
3...QFP, 4...White ceramic chip carrier, 5...Soldered round, 6...Overglaze, 7...Black overglaze. 11Z'Nia ζ Tuns 悉恢Fig. 1 Fig. 2 Procedure Neho Seibai (Method) 1) In the brief explanation section of the drawings in the specification, see ``4. Insert the following sentence on the line next to "Explanation". "FIG. 1 is a sectional view showing an example of a surface mount ceramic substrate according to the present invention, and FIG. 2 is a sectional view showing an example of a conventional surface mount ceramic substrate." 1988 Patent Application No. 218790 2 , Name of the invention Surface-mounted ceramic substrate 3, Relationship with the case of the person making the amendment

Claims (1)

[Claims] Surface-mounted parts such as ICs, transistors, etc. molded in black resin with good radiant energy absorption on a ceramic substrate with a circuit pattern made of thick film material, and chip carriers with an envelope made of white ceramic with poor radiant energy absorption. A surface mount ceramic substrate characterized in that, in the case of solder bonding, a white part other than the circuit pattern around the chip carrier having the white ceramic as an envelope is coated with a black insulating thick film material.