JPH0476990A - Bonding method for electric component - Google Patents

Abstract

PURPOSE:To snugly clamp an electronic component on a board and to effectively secure leads to solders by coating the board with a plurality of types bonds having different curing temperature, and adhering a molded form to the bonds. CONSTITUTION:The leads 4 of a board 1 are landed on solders 6, and a molded form 3 is adhered to the board 1 by bonds 7, 8. Here, the bond 7 is polymerized at an ambient temperature to exhibit adhesion. The bond 8 is an adhesive having higher curing temperature than that of the bond 7. Accordingly, while the solder 8 is being heated, an electronic component 2 is temporarily clamped on the board 1 by the adhesion of the bond 7, temporarily clamped by the adhesion of the bonds 7, 8 during soaking, then the adhesion of the bond 7 is lowered, and the component is temporarily clamped by the adhesion of the bond 8. Thus, the component 2 is not floated from the board 1 to be separated during a period until the solders 6 are heated, melted and then solidified.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a bonding method for electronic components, which involves bonding a molded electronic component to a substrate using multiple types of bonds with different curing temperatures, and then applying solder. It is heated to fix the leads to the solder.

(Prior art) As a means of bonding an electronic component having leads such as a QFP to a board, solder is formed on the board using plating means or a solder leveler, and the leads extending from the mold body are made to land on this solder. There is a known method of fixing leads to a substrate by heating and melting and solidifying them using reflow means.

In this type of bonding method, the electronic components are bonded to the board in advance to prevent them from lifting up and separating from the board until the solder hardens and the leads are firmly attached to the board. The electronic component is temporarily fixed by applying a bond and adhering a molded body to this bond.

(Problem to be Solved by the Invention) In the reflow method, solder is generally
It is gradually heated to about 0℃, and then the melting temperature of the solder (
Generally, it is heated to about 230°C, which is higher than about 183°C.

However, since there is no bond that can exhibit strong adhesive strength over a wide temperature range from room temperature to about 230 degrees Celsius, it is not possible to securely temporarily attach the molded body to the substrate, and the electronic components may lift up from the substrate during reflow. There was a problem that they were easy to separate.

(Means for Solving the Problems) The present invention allows leads extending from a molded body of an electronic component to land on solder formed on a substrate, and heats and melts and solidifies the solder using a reflow means, thereby attaching the leads to the substrate. In the bonding method for electronic components, a plurality of types of bonds having different curing temperatures are applied to the substrate, and the mold body is adhered to the bonds.

(Function) In the above configuration, since the mold body is bonded to the substrate using multiple types of bonds with different curing temperatures, the electronic The components are securely temporarily attached to the board, and the leads can be reliably attached to the solder.

(Example) Next, the present invention will be described in detail with reference to the drawings.

In FIG. 1, ■ is a board, and 2 is an electronic component. In this electronic component 2, leads 4 extend from a molded body 3. A circuit pattern 5 made of copper foil is formed on the upper surface of the substrate 1, and solder 6 is formed on the circuit pattern 5 by plating means or a solder leveler. The lead 4 has landed on this solder 6. 7. -8 is a temporary bond applied to the upper surface of the substrate 1, and the molded body 3 is adhered to the substrate 1 by this bond 7.8.

Bond 7, on the other hand, is an instant adhesive that undergoes a polymerization reaction at room temperature and exhibits strong adhesive strength in the temperature range from room temperature to about 150°C. For example, cyanoacrylate resin is known as such a bond having a relatively low curing temperature.

The other bond 8 is an adhesive with a higher curing temperature than the bond 7, which undergoes a polymerization reaction in the temperature range of about 100°C to 150°C, and exhibits strong adhesive strength at temperatures above about 100°C to 230°C. Demonstrate. Such an adhesive can be obtained, for example, by adding a peroxide, which initiates thermal polymerization, to an acrylic ester resin.

FIG. 2a shows a typical temperature profile of the reflow means. As shown in this temperature profile, in general, in reflow, the solder is gradually heated from room temperature to about 150°C, and then heated to this temperature for a while.
After soaking at ℃, the melting temperature of solder (183℃) or higher is 2.
The solder is melted by heating it all at once to about 30° C., and then solidified by gradually cooling it.

In the figure, b is the temperature characteristic of the bond 7, and C is the temperature characteristic of the bond 8. On the other hand, Bond 7 is about 150℃ from room temperature.
It has strong adhesive strength in the temperature range of . In addition, the other bond 8 is in a temperature range of 150°C or higher,
It has strong adhesive strength. Therefore, solder 6 is 150
While being heated to about .degree. C., the electronic component 2 is temporarily fixed to the substrate 1 by the adhesive force of one bond 7. 150 again
During soaking at ℃, it is temporarily fixed by the adhesive force of both bonds 7°8, and after that, the adhesive force of one bond 7 decreases rapidly, so it is temporarily fixed by the adhesive force of the other bond 8. .

In this way, the temporary fixing force of the electronic component 2 to the board 1 is
As the reflow progresses, both bonds 7 and 8 share the responsibility, so the electronic component 2 is held on the board from the time the lead 4 is mounted on the solder 6 until the solder 6 is heated and melted and solidified by the reflow. You can temporarily secure it firmly to prevent it from floating up and separating.

In this embodiment, the electronic component 2 is temporarily fixed using two types of bonds 7 and 8, but it may be temporarily fixed using three or more types of bonds. 2 to the substrate 1 strongly.

(Effects of the Invention) As explained above, the present invention allows the leads extending from the molded body of the electronic component to land on the solder formed on the board,
In a bonding method for electronic components in which leads are fixed to a substrate by heating and melting the solder to solidify it by reflow means, multiple types of bonds with different curing temperatures are applied to the substrate, and the bond is coated with the mold. Since the body is bonded, the electronic component can be securely temporarily attached to the board during reflow, and the leads can be securely fixed to the solder.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which FIG. 1 is a front view of an electronic component mounted on a board, and FIG. 2 is a temperature characteristic diagram. 1... Board 2... Electronic component 3... Mold body 4... Lead/Solder... Bond

Claims (1)

[Claims] An electronic device in which the leads extending from a molded body of an electronic component land on solder formed on a substrate, and the leads are fixed to the substrate by heating and melting and solidifying the solder using reflow means. A method for bonding electronic components, characterized in that a plurality of types of bonds having different curing temperatures are applied to the substrate, and the mold body is adhered to the bonds.