JPH0455418Y2 - - Google Patents

Description

[Detailed explanation of the invention] [Industrial application field] This invention can be used, for example, in small television receivers and FM
The present invention relates to a grounding structure for an electronic circuit board in a tuner of a receiver, which connects a ground circuit of the electronic circuit board on which components are mounted to a shield case that houses the board.

[Prior Art] FIGS. 2 and 3 show the structure of a conventional tuner, etc., in which a circuit board 3 is formed by patterning a conductive film 2 made of copper foil on the back surface of a board 1.
On top, chip parts such as resistors and capacitors 4,
It is equipped with a coil 5, etc., is housed in a shield case 6, and is incorporated into, for example, a small television device. In this case, as a grounding structure for making the grounding circuit of the circuit board 3 conductive to the shield case 6,
An opening 7 is formed in the bottom surface of the shield case 6 facing the conductive coating 2 to be grounded, a recess 8 is formed around the opening 7, and the outside of the shield case 6 is formed in the recess 8 and the opening 7. The solder 9 is melted and solidified into the recess 8 of the shield case 6.
The inner surface 7a of the opening 7 and the conductive film 2 on the back surface of the substrate 1 are electrically connected to each other by solder.

[Problems that the invention attempts to solve] By the way, when the chip parts 4, coil 5, etc. are mounted on the board 1,
When performing so-called surface mounting in which the terminals 4a and 5a and the land 10 are fixed with solder to the land 10 formed on the surface of the board 1, cream solder is applied to the terminals 4a and 5a and the land 10 in advance, instead of soldering them individually. The entire solder is placed in a reflow oven (not shown) to melt the cream solder and melt it into the corresponding part. However, in the case of the conventional grounding structure as described above, the soldering part is on the back side of the board 1, so after the above soldering is completed, the circuit board 3 is housed in the shield case 6 and fixed, and the shield Flip the case 6 upside down and open the opening 7.
The solder 9 must also be melted into the recess 8, and the soldering must be done manually in addition to the reflow oven process described above. In addition, although the shield case 6 uses a thin steel plate plated with tin, the inner surface 7a of the opening 7 has a broken surface exposed, and the weldability of the solder 9 is poor if left as is, so tin plating must be performed again. Must be. Furthermore, in the structure shown in Figure 3, solder 9 is used to make the welding firm.
It is necessary to cover the top of the recess 8,
Therefore, the solder 9 bulges in the center of the opening 7, and the bulge of the solder 9 gets in the way when the shield case 6 is installed in a small space such as a small television receiver that uses a liquid crystal as an image element. There was a problem with becoming. Further, since the bonding structure between the substrate 1 and the solder 9 is planar, there is a possibility that the bond may come off when a tensile force due to distortion of the substrate 1 is applied.

This invention aims to solve the various problems mentioned above by simple means.

[Means for Solving the Problems] In order to solve the above problems, this invention forms a through hole whose inner surface is covered with a conductive film in the circuit board, and on the other hand, in the shield case, A mountain-shaped protrusion to be inserted into the above-mentioned through-hole is formed by press working, and the protrusion is brazed to the conductive coating on the inner surface of the through-hole.The protrusion formed on the shield case is usually located on the bottom surface. is suitable, but any suitable position facing the substrate is adopted.

[Function] In such a grounding structure for an electronic circuit board, with the protrusion inserted into the through hole, the connection between the protrusion and the through hole is made from one side of the through hole (the side opposite to the side where the protrusion is inserted). By melting the solder into the gap, the protrusion and the conductive coating on the inner surface of the through hole are soldered together, and the grounding circuit of the electronic circuit board is grounded to the shield case. Therefore, in the case of surface mounting, soldering to the shield case can be performed at the same time as the step of soldering components in a reflow oven. No work is required to provide an opening in the shield case, and no plating work is required on the inner surface of the opening. Since the soldering structure is three-dimensional, the fixing strength is high and joint failures are less likely to occur. Further, no protrusion is formed to the outside of the shield case.

[Example] Hereinafter, an example of this invention will be described with reference to FIG. Note that the same reference numerals are used for the same parts as in the conventional example, and the description thereof will be omitted.

In FIG. 1, through holes 11 are formed at appropriate locations on a substrate 1, and a conductive coating 12 made of copper foil is formed on the inner surface of the through holes 11.
is formed by plating. This conductive film 12 is connected to a conductive film 2 patterned on the back surface of the substrate 1. The shield case 6 is formed from a tin-plated steel plate, and a circular recess 1 having a diameter larger than the through hole 11 in plan view is provided at a portion of the shield case 6 facing the through hole 11.
3 is formed to be concave on the inner surface, and a protrusion 14 that protrudes further inward in the shape of a conical surface is formed at the center thereof. These recesses 13 and protrusions 14 are press-molded at the same time when the shield case 6 is formed. The upper surface of the recess 13 is coated with an insulating coating 15.
contacts the conductive coating 2 on the back surface of the substrate 1 via the
Further, the projection 14 is inserted into the through hole 11, and a space R surrounded by the inner surface of the through hole 11, the outer surface of the projection 14, and the upper surface of the recess 13 is filled with solder 16. Through hole 1
The inner surface of the projection 1 and the outer surface of the protrusion 14 are brazed (soldered). This soldering is performed simultaneously when connecting the terminals 4a and 5a of the chip component 4 and the coil 5 to the land (conductive coating) 10 on the upper surface of the substrate 1. That is, the terminals 4a, 5a
Similarly, cream solder is applied to the space R inside the through hole 11, and when the circuit board 3 is loaded into a reflow oven, the cream solder melts and the gap S formed by the details in the space R and the insulating coating 15 is removed. When the solder 16 is removed from the furnace, the solder 16 solidifies and the soldering is completed. At this time, since the conductive coating 12 on the inner surface of the through hole 11 and the outer surface of the protrusion 14 are bonded, the area to be soldered is wider than in the case of planar bonding, and the bonded part is structured in three dimensions. Since the solder 16 is melted into the gap S, the fixing strength is dramatically increased.

[Effect of the invention] According to this invention, the protrusions provided on the shield case have a shape that can be easily provided on the steel plate by press working, and therefore, the protrusions provided on the shield case can be formed at the same time as the press forming for forming the shield case. Can be molded. In other words, there is no need for a separate member or process for providing the protrusion on the shield case. Furthermore, when brazing the shield case and the board, the melting direction of the solder (solder, etc.) can be the same as when soldering components for surface mounting. It can be done at the same time, saving you the trouble of doing it manually in a separate process. It also eliminates the hassle of plating the inner surface of the opening drilled in the shield case. Furthermore, the solder does not bulge out from the bottom of the shield case, so there is no problem at all when incorporating it into a small set. Furthermore, it has excellent effects such as high strength fixing with a small amount of solder and high reliability of the grounding structure.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of this invention, FIG. 2 is a perspective view of a conventional example, and FIG. 3 is a sectional view of a conventional example. DESCRIPTION OF SYMBOLS 1... Board, 2... Conductive film, 3... Circuit board, 6... Shield case, 11... Through hole, 1
2... Conductive film, 14... Protrusion, 16... Solder.

Claims (1)

[Scope of utility model registration request] The electronic circuit board includes an electronic circuit board on which a conductive film is formed on the surface of the board, and a shield case made of a steel plate that houses the electronic circuit board, and the electronic circuit board has an inner surface covered with a conductive film. A through hole is formed in the shield case, and a conical projection to be inserted into the through hole is formed by press molding.
1. A grounding structure for an electronic circuit board, wherein the conductive coating on the inner surface of the through hole and the protrusion are brazed.