JPH04269893A - Mounting structure for electronic component - Google Patents

Abstract

PURPOSE:To effectively secure an electronic component placed on a printed board by supplying adhesive to a printed board at the time of heating, placing the component on the adhesive, and soldering a conductor of the board to the electrode of the component also by thermally polymerizing the adhesive. CONSTITUTION:Adhesive 4 exhibiting liquid or semisolid state at an ambient temperature sequentially coat on a position to be placed with an electronic component 5. A printed board 1 is set in an electronic component automatic placing unit, chip electronic components 5 are sequentially placed on the adhesive 4, and sufficiently pressurized to adhere the component 5 on the adhesive 4. The board 1 is heated by radiation heat of a panel heater, etc., or hot blast to melt solder paste 3, thereby soldering a land 2 to be soldered of the board 1 to the electrode 6 of the component 5. Thus, the component 5 is effectively placed and secured on the board 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board mounting structure that can be used in television receivers, video tape recorders, electronic computers, and the like.

0002

[Prior art] Conventionally, chip resistors, chip capacitors,
To fix electronic components such as mini-mold transistors to a printed circuit board, first apply a light-curing adhesive to the printed circuit board, then mount the electronic components, and then bond by applying ultraviolet rays or using a combination of this and heating. Electronic components are fixed by curing the agent (Japanese Patent Laid-Open No. 54-826
68, JP-A-54-104573, and JP-A-54-98968). A method has also been proposed in which after applying a photocurable adhesive, the adhesive is pre-irradiated with ultraviolet rays to thicken or gel the adhesive, and then electronic components are mounted and fixed (Japanese Patent Application Laid-Open No. 1983-1999-1). 180090, JP-A-63-72195).

0003

[Problems to be Solved by the Invention] However, although any of the above methods can prevent the misalignment of electronic components on a printed circuit board, they require an ultraviolet irradiation device during the electronic component mounting process. This method has problems in that it requires space and the process is complicated.

[0004] Furthermore, when the above method is applied to mounting electronic components using solder paste, the solder paste on the board does not melt uniformly when heated, and as a result, the electronic components lift up due to the surface tension of the solder. This may cause problems such as shifting or misalignment. Furthermore, if the wettability of the solder to the electrode surface of the electronic component is poor, the electrode of the electronic component may be lifted off the printed circuit board, making it impossible to perform reliable soldering.

[0005]

[Means for Solving the Problems] Therefore, the present inventors solved the drawbacks of the conventional electronic component mounting method, and the process was relatively simplified, and the electronic components mounted on the printed circuit board were not misaligned. The present invention was completed after conducting research to find a mounting method and structure that can securely fix the problem without causing any problems.

That is, the present invention comprises a step of supplying an adhesive that is in a liquid or semi-solid state at room temperature onto a printed circuit board under heating; a step of mounting an electronic component on the supplied adhesive; The present invention provides an electronic component mounting structure obtained from a process including a step of heating the adhesive so that the adhesive is also thermally polymerized when soldering the conductor of the printed circuit board and the electrode of the electronic component.

[0007]

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

FIGS. 1 to 4 are process diagrams for obtaining the mounting structure of the present invention.

In the process shown in FIG. 1, solder paste 3 is first applied to soldering lands 2 on printed circuit board 1 by means such as screen printing.

Next, in the process shown in FIG. 2, the adhesive 4, which is liquid or semi-solid at room temperature, is preferably applied to the location where the electronic component 5 is to be mounted, using a heated and pressurized dispenser or the like. are heated to 40 to 80°C and applied sequentially. If the heating temperature of the adhesive is less than 40℃, the viscosity will not decrease as much due to heating of the resin, resulting in poor fluidity and poor application workability.If the adhesive is heated above 80℃, it will harden due to heat. This is not preferable as it makes it easier. The melt viscosity of the adhesive 4 at the coating temperature is 30 to 300 poise,
Preferably, the viscosity is 100 to 200 poise (viscosity at a shear rate of 100/sec) from the viewpoint of dischargeability (coating property), resin dripping property, and cohesive property.

[0011] The adhesive used in this case has durability,
Thermosetting adhesives are preferred in terms of heat resistance and reliability.
In particular, adhesives containing epoxy resin as a main component are preferred. It goes without saying that other resins may be mixed as long as the epoxy resin is contained as the main component. When such adhesives are thermally polymerized during the heating process during soldering, they eliminate pressure-sensitive adhesive properties and improve heat resistance, so they do not soften or flow when heated during solder melting, and prevent misalignment of electronic components. It can be prevented.

Next, the printed circuit board 1 is set on an electronic component automatic mounting machine, and as shown in FIG.
are sequentially mounted on the adhesive 4 one by one, and sufficiently pressurized with a mount head to reliably adhere the electronic components 5 onto the adhesive 4. Moreover, by preheating the printed circuit board 1 on which the electronic component 5 is mounted at this time, the electronic component 5 can be reliably temporarily fixed with the adhesive 4. By bonding in this way, it is possible not only to prevent the printed circuit board 1 from shifting due to vibrations during high-speed movement, but also to prevent the soldering lands 2 from melting during the reflow of the solder paste 3 during heating in the process described later. It is also possible to prevent the electronic components 5 from being lifted up due to non-uniform melting on the printed circuit board.

In the solder reflow process, the printed circuit board 1 is usually heated with radiant heat from a panel heater or the like, or the printed circuit board 1 is heated with hot air to melt the solder paste 3, and the soldering lands 2 of the printed circuit board 1 and the electronics are heated. The electrode 6 of the component 5 may be soldered as shown in FIG.

[0014]

[Effects of the Invention] As described above, in the electronic component mounting structure of the present invention, the viscosity of the adhesive is reduced by applying a liquid or semi-solid adhesive at room temperature to a printed circuit board under heating. This improves coating workability, and since the adhesive returns to room temperature immediately after application, it loses fluidity and develops cohesion. This provides the effect that electronic components can be reliably mounted and fixed onto a printed circuit board without shifting their positions.

[Brief explanation of the drawing]

FIG. 1 is a process diagram of one example showing a mounting structure of an electronic component according to the present invention.

FIG. 2 is a process diagram of one example showing a mounting structure of an electronic component according to the present invention.

FIG. 3 is a process diagram of one example showing a mounting structure of an electronic component according to the present invention.

FIG. 4 is a process diagram of one example showing a mounting structure of an electronic component according to the present invention.

[Explanation of symbols]

1 Printed circuit board 2 Soldering land 3 Solder paste 4. Adhesive 5　Electronic parts 6 Electrode

Claims (3)

[Claims] 1. A step of supplying an adhesive that is liquid or semi-solid at room temperature onto a printed circuit board under heating; a step of mounting an electronic component on the supplied adhesive; and a step of mounting an electronic component on the supplied adhesive. A mounting structure for an electronic component obtained from a process including a step of heating the adhesive so that the adhesive is thermally polymerized when soldering a conductor and an electrode of the electronic component. 2. The electronic component mounting structure according to claim 1, further comprising the step of preheating the printed circuit board on which the electronic component is mounted. 3. The electronic component mounting structure according to claim 1, further comprising the step of supplying a solder paste for connecting the conductor of the printed circuit board and the electrode of the electronic component.