JPH0799260A - Circuit device and mounting method thereof - Google Patents

Abstract

PURPOSE:To achieve high density mounting by fixing only the bottom surface of a hybrid integrated circuit on a substrate made of resin with solders, and mounting the leadless surface-mounting type hybrid integrated circuit simply and securely. CONSTITUTION:Each hybrid integrated circuit 15 is mounted on a mother board 12 so that electrodes 17a and 17b of the circuit are mounted on solders 14 of solder lands 13a and 13b. The entire body is made to pass through a reflow furnace. Then, the solders 14 on the solder lands 13a and 13b are heated and fused. After the device goes out of the reflow furnace, the solders 14 are cooled, and the electrodes 17a and 17b of the hybrid integrated circuit 15 are fixed on the solder lands 13a and 13b on the mother board 12. Therefore, only the bottom face of the hybrid integrated circuit 15 are soldered to the mother board 12. Thus, the space around the hybrid integrated circuit 15 becomes wide, and the mounting can be performed at high density. The short circuit of the neighboring solders 14 of the hybrid integrated circuit 15 can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit device adopting a mounting method in which only the bottom surface of a hybrid integrated circuit in which a surface mounting component (SMD) is mounted on a mounting substrate made of resin such as PCB is fixed by soldering. And how to implement it.

[0002]

2. Description of the Related Art Conventionally, as an example of a circuit device of this type, a mounting structure as shown in the sectional view of FIG. 4 has been used.

This circuit device 1 has electrodes 5a, 5 of a plurality of hybrid integrated circuits 4 on required solder lands 3a, 3b of a mother board 2 made of a resin substrate such as a glass epoxy substrate.
b is fixed by reflow solder 6, and each hybrid integrated circuit 4 is formed by mounting a leadless surface mount component on a ceramic substrate.

That is, the solder land 3 of the mother board 2
The patterns of the solder 6 are formed on the a and 3b by printing or the like, and the electrodes 5a and 5b of the hybrid integrated circuit 4 are placed on the patterns of the solder 6 and the whole of the pattern, for example, white in the figure. It is moved in the direction shown by the arrow and is passed through a reflow furnace to be heated.

Then, each solder 6 is connected to the solder lands 3a and 3b.
It is melted above and fixed to the electrodes 5a and 5b of the hybrid integrated circuit 4. At that time, the solder 6 is applied to the side surface of the electrode 5 on the side surface portion of the hybrid integrated circuit 4 so that the fillet 6 of the divergent edge rises upward in the figure.
Although a is formed, the presence or absence of the fillet 6a can be visually checked to determine whether or not the solder 6 is firmly fixed.

That is, when the presence of the fillet 6a of the solder 6 is visually confirmed, it can be determined that the solder 6 is firmly fixed, and when the absence of the fillet 6a is visually confirmed, It can be determined that the fixation of the solder 6 is defective.

As the hybrid integrated circuit 4, there are various hybrid integrated circuits 4a and 4b shown in FIGS. 5 and 6, respectively. These electrodes 5a and 5b are made of a ceramic circuit board of the hybrid integrated circuit 4, for example. 7 is formed continuously on the side surface and the bottom surface. Reference numeral 8 in the figure is a cap made of resin or metal.

[0008]

However, in such a conventional circuit device 1, since the fillet 6a of the solder 6 is formed around the hybrid integrated circuit 4, a space around the hybrid integrated circuit 4 is required accordingly. Therefore, there is a problem that the high density mounting is hindered or the adjacent fillets 6a are easily electrically short-circuited when the hybrid integrated circuit 4 is mounted at a high density.

Further, while the mother board 2 is made of resin such as glass epoxy, the circuit board 7 of the hybrid integrated circuit 4 is used.
Since they are made of ceramics, they have different coefficients of thermal expansion, so that when heated by a reflow furnace, the mother board 2 expands in the direction of the arrow in the figure as shown in FIG. 7, while the circuit board 7 is bent and deformed. To do. For this reason, as shown in FIG. 8, stress may be generated in the fillet 6a of the solder 6 and the like, and the crack 9 may be generated, which may reduce or lose the fixing force of the solder 6.

Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to easily and surely mount a leadless surface mount type hybrid integrated circuit on a resin substrate. It is an object of the present invention to provide a leadless surface mounting type circuit device capable of high-density mounting and a mounting method thereof.

[0011]

The present invention is configured as follows in order to solve the above-mentioned problems.

The invention according to claim 1 of the present application (hereinafter, referred to as the first
Of the invention) is a circuit device for mounting a leadless surface mounting type hybrid integrated circuit in which surface mounting components are mounted on a ceramic substrate on a resin substrate. It is characterized in that only the bottom surface of the integrated circuit is mounted by fixing with solder.

The invention according to claim 2 of the present application (hereinafter referred to as the second invention) is characterized in that the hybrid integrated circuit is a copper thick film printed board made of ceramics.

Further, in the invention according to claim 3 of the present application (hereinafter referred to as the third invention), the solder land of the resin substrate and the solder land of the hybrid integrated circuit to be soldered to this solder land are both It is characterized by being circular.

[0015]

[Action]

<First to Third Inventions> Only the bottom surface of the ceramic substrate of the leadless surface mounting type hybrid integrated circuit is fixed onto the solder land of the resin substrate by reflow soldering or the like, but the solder fixing is sufficient. It is strong.

That is, according to the present invention, even if the resin substrate and the ceramic substrate having different thermal expansion coefficients are thermally expanded, solder fillets that cause cracks are not formed, so that the two substrates are firmly fixed to each other. .

Moreover, after solidification of these solders, the solder fillet is formed mainly between the bottom surface of the ceramic hybrid integrated circuit and the resin substrate, and no solder fillet is formed around the hybrid integrated circuit. For this reason, the space around the hybrid integrated circuit becomes wider, and accordingly, the hybrid integrated circuit can be mounted on the resin substrate at a high density, and the adjacent solder fillets are electrically short-circuited. Can be prevented.

<Third Invention> Since both the solder lands of the resin substrate and the solder lands of the ceramic substrate are circular, the solder between the solder lands becomes substantially spherical when solidified. For this reason, even if the resin substrate and the ceramic substrate have different coefficients of thermal expansion, the difference in expansion between them can be absorbed from almost any direction by the substantially spherical solder, and thus cracks occur in the solder. It is possible to prevent the decrease or loss of the adhesive strength of the solder.

[0019]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3, the same or corresponding parts are designated by the same reference numerals.

FIG. 1 is a longitudinal sectional view of an essential part of an embodiment of a circuit device including the first to third, sixth and seventh inventions of the present application. In FIG. 1, the circuit device 11 is made of glass epoxy resin or the like. A plurality of solder lands 13a and 13b are formed on the mother board 12, which is a resin substrate, by screen printing or the like, and an appropriate amount of solder 14 is added to each of the solder lands 13a and 13b by screen printing or the like.

On the other hand, the hybrid integrated circuit 15 is formed by printing a copper paste or the like on a circuit board 16 made of ceramics or the like having a different coefficient of thermal expansion from the mother board 12 made of resin or the like to form leads (not shown). It is mounted on a ceramic-less copper thick film printed circuit board.

Each hybrid integrated circuit 15 is connected to the circuit board 1
The electrodes 17a and 17b are formed only on the bottom surface of 6 and not on the side surfaces as in the conventional example.

Therefore, each of these hybrid integrated circuits 15 is
The electrodes 17a and 17b are solder lands 13a and 13b, respectively.
After being placed on the mother board 12 so as to be placed on each solder 14, the whole is moved as shown by a white arrow in the drawing and passed through a reflow furnace (not shown). Then, the solder 14 on each solder land 13a, 13b is heated and melted in the reflow furnace, and after the solder 14 is discharged from the reflow furnace, the solder 14 is cooled and the electrodes 17a, 17b of the hybrid integrated circuit 15 are
The solder lands 13a and 13b on the mother board 12 are fixed.

Therefore, according to the present embodiment, only the bottom surface of the hybrid integrated circuit 15 is soldered to the motherboard 12, so that the fillet 6a of the solder 6 as shown in FIG. 4) is not formed. As a result, each hybrid integrated circuit 1 on the motherboard 12
Since the space around 5 is widened, the hybrid integrated circuits 15 can be mounted at a high density by that amount, and the solders 14 of the adjacent hybrid integrated circuits 15 can be prevented from being short-circuited.

Further, since the solder fillet 6a is not formed on the side surface of each hybrid integrated circuit 15, it is possible to prevent the solder fillet 6 from being cracked and the fixing force of the solder 14 from being lowered or lost.

FIG. 2 is a vertical sectional view of an embodiment including the fourth and fifth inventions of the present application. This circuit device 21 has solder 14 on the mother board 12 around each solder land 13a, 13b.
The solder 22 is coated on the side surfaces of the hybrid integrated circuit 15 in the vicinity of the electrodes 17a and 17b by coating the resist 22 to prevent the solder from adhering or flowing. It is characterized in that it has reduced wettability.

That is, the electrode 17 on the bottom surface of the hybrid integrated circuit
Since the resist 22 is coated on the side surface in the vicinity of a and 17b, when the solder is heated by the reflow furnace, the solder 1
It is possible to prevent the formation of the fillet 6a (see FIG. 4) which is melted by 4 and rises on the side surface of the hybrid integrated circuit.

Further, since both the solder lands 13a and 13b and the electrodes 17a and 1b are both formed in a circular shape, the solder 14 on each of the solder lands 13a and 13b is flat as shown in FIG. 3 during heating. It is formed into a spherical shape.

For this reason, as shown in FIG. 7, the difference in thermal expansion between the mother board 2 and the circuit board 7 of the hybrid integrated circuit, which is formed due to the difference in coefficient of thermal expansion, can be absorbed by these spherical solders 14 from all directions. Therefore, it is possible to prevent the crack 8 (see FIG. 8) of the solder 6 due to the difference in elongation from occurring.

In the above embodiment, the solder lands 13a,
The case where both 13b and the electrodes 17a and 17b are circular has been described, but it is not always necessary to have a perfect circle.
It may be oval. Further, in the above embodiment, the solder 14
Although the case of coating the resist 22 as the treatment for reducing the wettability of the solder has been described, the wettability of the solder may be reduced by forming an oxide film by oxidation.
The method is not limited.

Further, the electrodes and solder lands described above mean only the portions for electrical connection, and the portions covered with resist, for example, do not correspond to these.

[0032]

As described above, in the first to third inventions of the present application, only the electrodes on the bottom surface of the leadless surface mounting type hybrid integrated circuit are fixed to the solder lands of the resin substrate by soldering. It is possible to prevent a solder fillet from being formed around the hybrid integrated circuit.

Therefore, the hybrid integrated circuit can be mounted on the resin substrate at a high density, and the solders of the adjacent hybrid integrated circuits can be prevented from being electrically short-circuited.

Further, since both the solder land of the resin substrate and the bottom surface of the hybrid integrated circuit are formed in a circular shape, the solder interposed between them can be formed in a substantially spherical shape, and the solder integration with the substrate is performed. Since the difference in expansion between the circuit and the circuit board can be absorbed from all directions by this spherical solder, it is possible to prevent cracks from occurring in the solder.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a main part of a hybrid integrated circuit including the first to third, sixth and seventh inventions of the present application.

FIG. 2 is a longitudinal sectional view of a main part of a hybrid integrated circuit including the fourth and fifth inventions of the present application.

FIG. 3 is a partially enlarged view of FIG.

FIG. 4 is a partial vertical cross-sectional view of a conventional hybrid integrated circuit.

FIG. 5 is a perspective view of a conventional hybrid integrated circuit.

FIG. 6 is a perspective view of another conventional hybrid integrated circuit.

FIG. 7 is a diagram showing thermal expansions of a mother board and a circuit board in the conventional hybrid integrated circuit shown in FIG. 4, respectively.

FIG. 8 is a partially enlarged view of the conventional hybrid integrated circuit shown in FIG. 4 when a crack occurs in solder.

[Explanation of symbols]

 11 circuit device 12 motherboard 13a, 13b solder land 14 solder 15 hybrid integrated circuit 16 circuit board 17a, 17b electrode 22 resist

Claims (3)

[Claims] 1. A circuit device for mounting a leadless surface-mount type hybrid integrated circuit in which surface-mount components are mounted on a ceramic substrate on a resin substrate, wherein the hybrid integrated circuit is mounted on the resin substrate. A circuit device in which only the bottom surface of the circuit is mounted by being fixed by soldering. 2. The circuit device according to claim 1, wherein the hybrid integrated circuit is a ceramic copper thick film printed circuit board. 3. The circuit device according to claim 1, wherein the solder land of the resin substrate and the solder land of the hybrid integrated circuit soldered to the solder land are both circular.