JPH057075A - Electronic part packaging method - Google Patents

Abstract

PURPOSE:To make one time melting down step suffice for a solder paste by a method wherein the specific positions on one surface of a circuit substrate are coated with a solder paste and a thermosetting bonding agent; a mounted electronic part is heated to set the bonding agent; the specific positions on the other surface are also coated with the solder paste; and then the mounted electronic part is heated at the temperature exceeding the solder melting point so as to perform the soldering step. CONSTITUTION:The pads on one surface of a circuit substrate 1 are coated with a solder paste 2 while the central part of the substrate 1 is coated with a thermosetting bonding agent 4. Next, an electronic part 3b is mounted so that the central part on the rear surface of the electronic part 3b may come into contact with the bonding agent 4 while the electrode part with the solder paste 2. Next the electronic part 3b is heated at the temperature exceeding the setting temperature of the bonding agent 4 but not exceeding the solder melting point. After inverting the circuit substrate 1, the pads on the surface are coated with the solder and then the other electronic part 3c is mounted so that the electrode parts thereof 3c may come into contact with the solder paste 2. Next, the electronic part 3c is heated at the temperature exceeding the solder melting point to melt down the solder. Through these procedures, the electronic parts 3b, 3c can be packaged on both surfaces of the circuit substrate 1 by performing one time solder melting down step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mounting electronic parts.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional example of an electronic component mounting method. As shown in the figure, first, the solder paste 2 is applied to one surface of the circuit board 1, the electronic component 3 is mounted thereon, and the solder paste is heated to a temperature higher than the melting point of the solder. Make an attachment.

Next, the circuit board 1 is turned upside down, the solder paste 2 is applied to the other surface of the circuit board 1, and another electronic component 3a is mounted thereon, and then the temperature is again set to a temperature higher than the melting point of the solder. Heat and solder.

By doing so, the electronic components 3 and 3a are mounted on both surfaces of the circuit board 1.

[0005]

In the above-mentioned prior art, 2
During the second heating, the electronic components on the lower surface of the circuit board are held by the surface tension of the molten solder. Therefore, an electronic component that receives gravity greater than the surface tension will fall, and an electronic component with a large weight cannot be mounted.

Further, since the electronic component on one surface is subjected to a temperature equal to or higher than the melting point of the solder twice, the electronic component is greatly damaged by heat, and the solder is melted twice, so that the soldering strength is lowered. There is a problem to do.

The present invention has been made in view of the above points, and an object of the present invention is to provide an electronic component mounting method capable of mounting a heavy electronic component and improving reliability. Is.

[0008]

The above object is to apply a solder paste and a thermosetting adhesive to predetermined positions on one surface of a circuit board, and to apply the solder paste and the thermosetting adhesive to the lower surface thereof. After mounting the electronic components so that they come into contact with each other, heat the adhesive at a temperature not lower than the curing temperature of the adhesive and lower than the melting point of the solder to cure the adhesive, and then turn the circuit board over to the other surface of the circuit board. This is achieved by applying a solder paste to a predetermined position of (1), mounting another electronic component on this solder paste, and then heating at a temperature equal to or higher than the melting point of the solder for soldering.

[0009]

Since the above means is provided, the electronic components on the lower surface of the circuit board can be fixed to the circuit board with the thermosetting adhesive, and the solder paste can be melted only once.

[0010]

EXAMPLES Next, the present invention will be specifically described by way of examples.

[Embodiment 1] FIG. 1 shows an embodiment of the present invention. Since the same parts as those in the past are designated by the same reference numerals, the description thereof will be omitted. In this embodiment, the solder paste 2 and the thermosetting adhesive 4 are applied to predetermined positions on one surface of the circuit board 1, and the applied solder paste 2 is applied.
And after mounting the electronic component 3b on the thermosetting adhesive 4 so that the lower surface thereof comes into contact, at a temperature equal to or higher than the curing temperature of the adhesive 4,
Moreover, the adhesive 4 is cured by heating at a temperature lower than the melting point of the solder 2, then the circuit board 1 is inverted and the solder paste 2 is applied to a predetermined position on the other surface of the circuit board 1, and the solder paste 2 is applied on the solder paste. After mounting the other electronic component 3c, heating was performed at a temperature equal to or higher than the melting point of the solder 2 for soldering.
By doing so, the electronic component 3 on the lower surface of the circuit board
b is fixed to the circuit board 1 with the thermosetting adhesive 4, and the solder paste 2 only needs to be melted once, so that heavy electric components 3b and 3c can be mounted.
The damage to the electronic component 3b due to heat is smaller than the conventional one, and the soldering strength is improved as compared with the conventional one. It is possible to mount the heavy electronic component 3b, 3c and improve the reliability. An electronic component mounting method can be obtained.

That is, the solder paste 2 is applied to the pad on one surface of the circuit board 1 and the thermosetting adhesive 4 is applied to the center thereof. Next, the electronic component 3b is mounted such that the central portion of the lower surface of the electronic component 3b contacts the thermosetting adhesive 4 and the electrode portion of the electronic component 3b contacts the solder paste 2. Next, the adhesive 4 is cured by heating it to a temperature (about 150 ° C.) higher than the curing temperature of the thermosetting adhesive 4 and lower than the melting point of the solder. Next, after the circuit board 1 is turned over, the solder paste 2 is applied to the pad on the other surface, and the other electronic components 3
The electronic component 3c is mounted so that the electrode portion of c contacts the solder paste 2. Finally, the solder paste 2 is melted by heating it to a temperature equal to or higher than the melting point of the solder 2. By doing so, the electronic components 3b and 3c are mounted on both surfaces of the circuit board 1.

As described above, according to this embodiment, the following effects can be obtained.

(1) To fix electronic parts with an adhesive,
It is possible to fix heavy electronic components on both sides of the circuit board.

(2) Since the heat applied to the electronic parts is reduced, the damage to the electronic parts due to the heat is small.

(3) The soldering strength is high because the solder is melted once.

(4) Since the solder paste can be supplied on both sides by printing, the pad spacing can be reduced and the mounting density can be increased.

The curing temperature of the thermosetting adhesive is preferably as low as possible, preferably 150 ° C. or lower.

[0019]

As described above, according to the present invention, the solder paste and the thermosetting adhesive are applied to predetermined positions on one surface of the circuit board, respectively, and the solder paste and the thermosetting adhesive thus applied are coated on the lower surface thereof. After mounting the electronic components so that they come into contact with each other, heat the adhesive at a temperature not lower than the curing temperature of the adhesive and lower than the melting point of the solder to cure the adhesive, and then turn the circuit board over to the other surface of the circuit board. After applying the solder paste to the prescribed position of this, and mounting other electronic components on this solder paste, heating was performed at a temperature above the melting point of the solder to perform soldering, so the electronic components on the lower surface of the circuit board were thermoset. Since it can be fixed to the circuit board with a mold adhesive and the solder paste only needs to be melted once, heavy electrical parts can be mounted, and heat damage to electronic parts compared to the past Small, soldering strength is as improved conventionally, and allows the implementation of large electronic parts by weight, and it is possible to improve the reliability can and the obtained electronic component mounting method.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional side view showing a mounting state of an electronic component on a circuit board according to an embodiment of an electronic component mounting method of the present invention.

FIG. 2 is a vertical cross-sectional side view showing how electronic components are mounted on a circuit board by a conventional electronic component mounting method.

[Explanation of symbols]

 1 circuit board 2 solder paste 3b, 3c electronic component 4 thermosetting adhesive

Claims (1)

Claim: What is claimed is: 1. An electronic component mounting method for mounting electronic components on both surfaces of a circuit board, wherein a solder paste and a thermosetting adhesive are applied to predetermined positions on one surface of the circuit board, respectively. Then, after mounting the electronic component so that the lower surface of the applied solder paste and the thermosetting adhesive are in contact with each other, the adhesive is heated at a temperature not lower than the curing temperature of the adhesive and lower than the melting point of the solder. After the agent is cured, the circuit board is inverted and a solder paste is applied to a predetermined position on the other surface of the circuit board, and another electronic component is mounted on this solder paste, and then the temperature is equal to or higher than the melting point of the solder. An electronic component mounting method, characterized in that heating is performed by soldering.