JPH05226821A - Electronic component mounting method - Google Patents

Abstract

PURPOSE:To avoid defective soldering caused by the adhesion of adhesive to an electrode by a method wherein uncured thermosetting resin composition is applied to the component mounting part on a circuit board and heated to soften and, after an electronic component is mounted, cured by heat. CONSTITUTION:After a resist layer is formed on the surfaces of a circuit board 2 and an electrode 4, an adhesive layer 1 is formed on the circuit board 2. The adhesive is mainly composed of epoxy resin having epoxy functional groups or acrylate resin having acryloil groups. The printed adhesive layer 1 is semi- cured by a curing apparatus and, successively, re-heated. When the temperature of the adhesive layer 1 exceeds the softening point of the adhesive, an electronic component is mounted. The circuit board 2 is again heated by the curing apparatus or a reflow apparatus and the adhesive is completely cured to obtain an adhesion strength required in a next soldering process. With this constitution, adhesive coating using a barrel is not necessary and defective soldering caused by stringy adhesive can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component mounting method in which an electronic component is fixed to a circuit board with an adhesive and then soldered.

[0002]

2. Description of the Related Art Conventionally, when an electronic component is soldered on a circuit board, cream solder is applied to a joining electrode of the circuit board and an adhesive is applied to a mounting position of the electronic component, and the electronic component is applied onto the adhesive. By mounting the electronic components, the electronic components are temporarily fixed by adhesion, and then the circuit board is sent to a reflow furnace to solder the electronic components to the circuit board (for example, JP-A-3-163895 and JP-A-2-11099).
4 publication).

As an adhesive applying device, as shown in FIGS. 2 and 3, a barrel 8 filled with an adhesive is mounted on an XY robot 11, and air is blown into the barrel 8.
The adhesive was extruded from the nozzle 9 attached to the tip of the barrel 8. The position to apply the adhesive is determined by the XY robot, and after moving to that position,
The head descends and the tip of the nozzle contacts the substrate 2. At the same time, the electrically controlled opening / closing valve 10 is opened, and the barrel 8 is filled with air so that the adhesive is discharged and applied onto the substrate. After applying the adhesive, the head immediately rises and moves to the next point. The substrate coated with the adhesive immediately moves to the next electronic component mounting process, and is completed through the component mounting process, the adhesive curing process, and the soldering process.

The amount of adhesive applied varies depending on the air pressure, the opening time of the open / close valve, and the temperature of the tip of the nozzle.

[0005]

However, in such a conventional configuration, when the adhesive is applied to the substrate, the head 1 is used.
No. 4 rises at a high speed and moves, so the applied adhesive is stretched and the threads are applied in the form of a whisker, the application accuracy deteriorates, and the adhesive is applied to the board electrode part, causing soldering failure. It was. As for the adhesive to be used, viscosity characteristics with less stringiness and kinds of adhesives have been studied, but the stringing occurrence rate tends to increase as the coating tact speed increases.

The present invention solves such a problem by applying an adhesive without stringing, without being affected by the application conditions when applying the adhesive on the substrate and the application tact. The purpose is to fix electronic components.

[0007]

In order to solve this problem, the present invention provides a step of forming an uncured thermosetting resin composition in advance on a component mounting portion on a circuit board, and a printed resin composition. The electronic component is mounted on the substrate by a heating and softening step, an electronic component mounting step, and a resin composition thermosetting step.

[0008]

The epoxy resin and the acrylate resin are liquids containing the respective curing agents, and contain the filler and the thixotropic agent in a dispersed state in order to improve the printability. Printing is performed using a metal mask or a mesh mask, and the formed resin is heated at about 150 ° C. to be in a semi-cured state. This resin does not have tackiness at room temperature of 10 ° C to 40 ° C. Such a semi-cured resin exhibits tackiness when heated to 50 ° C. to 100 ° C. and reaching a temperature above the softening point.

An electronic component is mounted on a resin exhibiting adhesiveness, and the component is fixed by the adhesiveness. Finally, it is heated to a temperature of around 150 ° C. to be thermoset, and an adhesive force is developed between the uncured resin and the electronic component. Finally, it is soldered through a soldering process.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electronic component mounting method according to an embodiment of the present invention will be described below with reference to the drawings.

1A to 1E show an electronic component mounting process of this embodiment. As shown in the figure, a resist layer 3 is formed on the surfaces of the circuit board 2 and the electrodes 4. First,
The adhesive layer 1 is formed on the circuit board 2 (FIG. 1A).
The adhesive 1 has a novolac structure, bisphenol A or bisphenol F as a main skeleton, and an epoxy resin having an epoxy functional group or an acrylate resin having an acryloyl group as a main component. The curing reaction product of the acrylate resin preferably has a softening point of 50 ° C to 100 ° C. Further, an imidazole compound or an amine compound is mixed as a thermosetting agent for the epoxy resin, and a peroxide compound is mixed as a curing agent for the acrylate resin. In addition, inorganic fillers such as calcium carbonate and silicic acid compounds are mixed to obtain printability. The adhesive having the above composition is printed with a metal mask or a mesh mask. Ideally, the thickness of the mesh mask is 100 μm to 200 μm, and the thickness of the adhesive after printing is about 70 μm to 170 μm. As for the mesh mask, the condition that the film thickness after printing is equivalent to that when the metal mask is used is obtained. The printed adhesive layer 1 is semi-cured by a curing device (FIG. 1 (b)). Ideally, the curing device at this time is a dedicated curing device for the adhesive for electronic parts or a reflow device for soldering.
The curing condition is maintained at a temperature of 150 ° C. for 30 seconds to 60 seconds so that the curing rate is 30% to 70%. The semi-cured adhesive is apparently a cured product at room temperature. Subsequently, the semi-cured adhesive is reheated to 50 ° C. to 100 ° C. again, and when the temperature reaches the softening point of the adhesive, the adhesive exhibits tackiness (FIG. 1 (c )). Electronic components are mounted when the adhesive is softened. As the heating means, an adhesive curing device for electronic components is used in advance (FIG. 1 (d)). Since the temperature of the electronic component discharged from the apparatus immediately drops, it is desirable to install a heater b6 on the lower surface of the substrate holder of the electronic component mounting machine and heat it at a constant temperature (FIG. 1 (e)). The circuit board on which the components have been mounted is again processed by an adhesive curing device for electronic components or a reflow device for 150
The adhesive is completely cured by heating at a temperature of 60 ° C. for 60 to 120 seconds, and the necessary adhesive force is obtained in the next soldering step. According to this method, since the adhesive coating by the barrel is not performed, it is possible to prevent the occurrence of defective soldering due to the stringing.

[0012]

As is apparent from the above description of the embodiments, according to the present invention, the step of applying the adhesive by the barrel is eliminated, and the adhesive is applied to the electrode due to a beard-like application or a variation in the application amount. It is possible to prevent defective soldering caused by the adhesion of the solder, and it is possible to mount electronic parts with high reliability.

[Brief description of drawings]

FIG. 1 is a sectional view showing an electronic component mounting process according to an embodiment of the present invention.

FIG. 2 is a perspective view of a conventional electronic component mounting device.

FIG. 3 is a cross-sectional view of an adhesive application tip portion of the electronic component mounting apparatus.

[Explanation of symbols]

 1 Adhesive Layer 2 Substrate 3 Resist Layer 4 Electrode 5 Heater a 6 Heater b 7 Electronic Component

Continued Front Page (72) Hidenori Miyagawa, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A step of printing an uncured thermosetting resin composition on a component mounting portion on a circuit board to form an adhesive layer, and a heating and softening step of imparting tackiness to the adhesive layer.
A step of mounting an electronic component on the adhesive layer that has been softened by heating to exhibit adhesiveness, a step of thermally curing the adhesive layer on which the electronic component is mounted, and an electrode provided with the electronic component on a circuit board. An electronic component mounting method comprising a step of soldering to an electronic component. 2. The electronic component mounting method according to claim 1, wherein the thermosetting resin composition is mainly composed of an epoxy resin or an acrylate resin.