JPS5855601Y2 - molded electronic parts - Google Patents

Description

[Detailed Description of the Invention] The present invention is applicable to molded electronic components, especially molded electronic components that generate a large amount of self-heating, large molded electronic components such as coils and transformers, or molded electronic components that are placed close to a heating element. In particular, the molded part of the reeled wire is coated with a resilient resin such as silicone resin, and the entire body is molded with a hardening resin such as epoxy resin to reduce various stresses and shocks that occur in the lead wire or between the lead wires. The present invention relates to a new molded electronic component that can guarantee high reliability by devising a terminal structure that can be absorbed.

BACKGROUND OF THE INVENTION Today, many electronic devices are inserted into a corresponding portion of a printed wiring board by an automatic insertion machine and then soldered by an automatic soldering machine.

Furthermore, as automation and labor saving are increasingly required,
Large internal self-heating components, such as transformer coils, which previously could not be mounted on printed wiring boards, are now being mounted on printed wiring boards.

Furthermore, in order to effectively utilize space within the device, the board is often mounted close to other heat-generating components, such as the heat sink of a power transistor.

When a board is mounted close to a heat-generating component in this way, the board expands due to thermal radiation, which applies compressive or tensile force to some parts of the solder component lead wires attached to the board.

Today, many parts such as transformers that generate a large amount of self-heating are molded with resins such as epoxy, and the thermal expansion coefficients of the molding resin and printed wiring boards are generally different, so the difference in the thermal expansion coefficients of the two In other words, as the temperature rises, the component dimensions increase and the lead wire spacing also tends to widen. On the other hand, since the lead wires are soldered to the printed wiring board, the coefficient of thermal expansion of the printed wiring board increases. If it is smaller than that of the molding resin, a large force will be applied to the soldering part in a direction perpendicular to the lead wire.

In other words, each time the device is stopped, the temperature of the component or board rises and falls, force is repeatedly applied to the soldered part of the lead wire, and eventually cracks occur in the soldered part, resulting in poor soldering and reducing reliability. This was the cause of the deletion.

The present invention has been devised in view of this point, and will be described in detail below with reference to the drawings.

The drawing is a sectional view of an embodiment of the present invention.

In the figure, figure number 1 indicates a coil molded with a hardening resin 2 such as epoxy, and is connected to lead wires 3, 3 having a small tolerance and large diameter at the ends.

The molded portion of the lead wire 3.3 is separately molded into a cylindrical shape and coated with elastic resin 4, 4 such as silicone resin.

In the actual process, a cylindrical body having a film thickness calculated as described below is molded from silicone resin, and the lead wires are covered prior to molding.

Normally, the temperature of the board or the temperature of parts due to self-heating is at most about 80°C, and the thermal expansion coefficient of epoxy resin is 90 x 106 mm/mm-deg, so let's assume that the distance between component leads is 40 mm. Assuming that, the absolute value of the elongation is Q, 2 mm when compared to the lead wire spacing at 20°C.

Therefore, in order to absorb this elongation, it is sufficient that the resin thickness of the cylindrical portion of the silicone resins 4, 4 is about 1 mm.

With this structure, dimensional changes due to the difference in thermal expansion between the board and the molding resin are absorbed by the elastic lead wire sheathing resin, and no direct force is applied to the soldered part. Also, in the case of large, heavy parts, instantaneous external forces caused by vibrations and shocks are absorbed by this elastic resin, so no large force is applied to the soldered parts, greatly increasing the reliability of the soldered parts. improved, and the effect is significant.

[Brief explanation of the drawing]

The figure is a sectional view of one embodiment of the present invention. 1... Coil, 2... Hardening resin such as epoxy resin, 3... Lead wire, 4...
・Resin with elasticity such as silicone resin.

Claims (1)

[Scope of utility model registration request] The molded part of the node wire is covered with a relatively elastic resin, and the entire part is molded with a curable resin, and the stress that occurs between the lead wires based on the difference in thermal expansion coefficient between the molded resin and the printed board. Molded electronic components designed to absorb