JPS5928998B2 - How to attach electrical components without lead wires to a circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for attaching electrical components, particularly electrical components without lead wires, to a circuit board.

Conventional Structure and Problems Traditionally, electrical components without lead wires have electrode portions made of a silver-based conductor such as silver or silver-palladium on the end surface of the component body and on the upper and lower surfaces near the end surface. and
The electrode portion remains exposed without being coated for soldering.

Generally, when attaching such an electrical component without lead wires to a circuit board, the electrode portion of the electrical component without lead wires is placed opposite to the conductor foil provided on the circuit board, and the conductor foil portion and the electrode portion are connected to each other. are joined by soldering. At this time, it is common to bring the electrode portion into contact with the conductive foil portion, and then apply solder to the electrode portion in a bulging manner. By the way, in this case, most of the electrode part is covered with solder, but due to the flow of solder, the contact part with the conductor foil part and its surroundings are hardly covered with solder. .
Therefore, when using an electrical component that does not have a lead wire and uses silver or silver-based conductor materials such as silver-palladium for the electrode part, when an electric field is applied, the circuit board may absorb moisture, etc. There have been many problems, such as a phenomenon in which silver migrates between the electrodes and the conductor foil, resulting in a significant reduction in the insulation between the electrodes and short circuits. In other words, the silver migration phenomenon occurs when an electrode part made of a silver-based conductor is exposed to the air and absorbs moisture, and when there is a potential difference between the electrode part and the neighboring conductor foil part, which makes up the electrode part. The silver in the silver-based conductor crystallizes toward the adjacent conductor foil portion, and this grown silver causes a decrease in insulation and short circuit between the adjacent conductor foil portions. OBJECTS OF THE INVENTION An object of the present invention is to make the electrode portion of an electrical component having no lead wire correspond to a conductive foil provided on a circuit board, and to perform good solder bonding at that point, and to A circuit board for electrical components that can prevent insulation between electrodes from decreasing or short-circuiting due to silver migration phenomenon even when silver-based conductors such as silver or silver-palladium are used in the parts. The purpose is to provide an installation method for

Structure of the Invention In order to achieve the above object, the method of attaching an electrical component to a circuit board of the present invention is such that solder swells on the electrode portion of the electrical component that does not have a lead wire and is opposed to the conductor foil portion on the circuit board. Before joining the conductor foil part and the electrode part by soldering, a paste-like solder layer is formed on the conductor foil part of the circuit board, and the paste-like solder layer is used to bond the electrical component. The present invention is characterized in that the contact portion of the electrode portion with the conductor foil portion on the circuit board is also covered.

According to this configuration, the electrode portions of the electrical components are completely covered with solder, and are no longer exposed to the air and absorb moisture. Therefore, even if there is a potential difference between adjacent conductor foil portions, there is an advantage that insulation deterioration and shorting caused by the silver migration phenomenon can be prevented. DESCRIPTION OF EMBODIMENTS FIGS. 1 to 6 show an embodiment of the present invention. In FIGS. 1 to 6, 1 is a circuit board, and 2 and 2 are one main surface of the circuit board 1. 3 is a paste-like solder printed and coated on any part of the conductor foils 2, 2; 4 is a conductor foil formed on the circuit board 1;
Advantageously, a thermosetting adhesive, for example of an epoxy type, is used.

Reference numeral 5 denotes an electrical component having no lead wire, which is arranged to correspond to the conductor foils 2, 2 provided on the circuit board 1,
The electrode portions 6, 6 formed at both ends of the rod-shaped electric component 5 are disposed so as to correspond to the conductor foils 2, 2, and are attached to the paste-like solder layers 3, 3 formed on the conductor foils 2, 2. arranged to correspond.

The electrical component 5 having no lead wire is heated in advance before soldering and is temporarily fixed onto the circuit board 1 with a thermosetting adhesive layer 4. The electrical component 5 without lead wires is thus placed on the circuit board 1, and then the electrode parts 6, 6 are joined to the conductive foils 2, 2 by soldering 7, 7 at a temperature of 200-odd degrees. and is mounted and fixed on the circuit board 1 described above.

As described above, the electrode parts 6-A, 6-A at the upper position of the electrode parts 6, 6 are covered by the soldering 7, 7, and the electrode parts 6-A, 6-A at the lower position of the electrode parts 6, 6 are covered by the soldering. Since the portions 6-B and 6-B are covered with the paste-like solder layers 3 and 3, there is no inconvenience that the solder does not get into the electrode portion at the lower position unlike the conventional method, and this is reliable and It allows for strong solder joints.

Moreover, in the electrode portions 6-B and 6-B at the lower position, the paste-like solder 3, 3 forms a good solder joint layer during soldering with a soldering iron or automatic soldering. Even if the electrode parts 6, 6 of the electrical component 5 without lead wires are silver or silver-based electrodes such as silver-palladium, silver migration due to moisture absorption in the circuit board 1 etc. occurs when an electric field is present. It is possible to prevent problems such as a decrease in insulation between electrodes and shorts. Effects of the Invention As described above, according to the present invention, a paste-like solder layer is formed on the conductor foil of a circuit board, and the electrode portion of an electrical component having no lead wire is made to correspond to this layer, and then soldered. Therefore, the connection and fixation of electrical components to the circuit board by soldering can be made extremely reliable and strong.

According to the present invention, the electrode part of the electrical component is completely covered with the paste solder layer and normal solder, so even if the electrode part is coated with solder and exposed to the air, The part itself is less likely to absorb moisture, and even when the electrode part is made of a silver-based conductor such as silver or silver-palladium, no silver migration phenomenon occurs, which is extremely advantageous in practice.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a circuit board used in the method of attaching electrical components without lead wires to a circuit board according to the present invention, and Fig. 2 is a diagram showing a state in which a paste-like solder layer is formed on the same circuit board. , FIG. 3 is a diagram showing a state in which an adhesive for holding an electrical component is formed on the same circuit board, FIG. 4 is a diagram showing a state in which an electrical component without a lead wire is temporarily fixed to the same circuit board, and FIG. This figure is a cross-sectional view of FIG. 4, and FIG. 6 is a cross-sectional view showing a state in which electrical components without lead wires are soldered to the same circuit board. 1... Circuit board, 2... Conductor foil, 3.
... Paste solder layer, 4 ... Adhesive layer, 5 ... Electrical component without lead wire, 6 ...
...Electrode part, 7...Solder.

Claims (1)

[Claims] 1. Forming a paste-like solder layer on a conductive foil provided on a circuit board, and arranging the above-mentioned electrical component so that the electrode part of the electrical component without a lead wire faces the paste-like solder layer,
Thereafter, the electrode part and the conductive foil are soldered to cover the electrode part, thereby coating the electrode part of the electric component with solder and joining the electric part to the circuit board. How to attach electrical components to a circuit board.