JPH10107459A - Solder connecting structure and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a connecting structure between a printed board and a metal chassis by bending a cut-out tongue, provided with a recessed part toward inside a metal case, and solder/fixing between the inside peripheral surface side of the metal chassis at a free end of the tongue and a conductive pattern. SOLUTION: In a metal chassis 2, while across the side peripheral surface of a printed board 1, with a free end part 8b protruded above the rear surface of the printed board 1, a part of the free-end part 8b is made wider compared to a base part 8a, and a recessed part 8d is formed on the inside peripheral surface side of the metal chassis 2 of the free end part 8b. In addition, on the side closer to the base part 8a from the rear surface position of the printed board 1, a cut-out tongue 8, having a cut-out window on its both sides is provided. The cut-out tongue 8 is bent toward inside the metal case, and the inside peripheral surface side of the metal chassis of the free end part 8b of the cut-out tongue 8 and a conductive pattern 9 are solder/fixed together. Thereby, a strong connection strength against a shear stress generated in the direction of side periphery area of the printed board 1 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection structure of a printed circuit board and a metal chassis of an electronic circuit device having a structure in which a printed circuit board constituting an electronic circuit such as an electronic tuner is surrounded and shielded by a metal chassis.

[0002]

2. Description of the Related Art FIG.
Is a printed circuit board having electronic components (not shown) mounted on the front and back surfaces, a chip component is mounted on the back surface (exposed surface shown), and an electronic component with leads is mounted on the front surface side. Reference numeral 20 denotes a metal chassis, a frame 2 having a U-shaped cross section.
The intermediate portion of both leg pieces 0a is bridged by a plate 20b, and the printed circuit board 10 is held inside.

Reference numeral 30 denotes an input connector fixed to the frame 20a, and reference numeral 40 denotes a feedthrough capacitor fixed to the plate 20b. Here, a locking projection 50 and a pressing projection 60 formed by pressing are provided on the inner peripheral surface of the metal chassis 20, and the printed board 10 is locked by the projection 50 and temporarily fixed by the projection 60. In this state, the inner ends of the leads of the feedthrough capacitor 40 are not shown, but are soldered to the printed circuit board 10 in the metal chassis 20 and a ground conductive pattern (not shown) on the peripheral edge of the printed circuit board 10.
And the inner peripheral surface of the metal chassis 20 are connected by solder 70, and the printed circuit board 10 and the metal chassis 20 are fixed.

Conventionally, this soldering operation has been performed manually. However, stress is applied to the soldered portion 70 by a temperature cycle test due to a difference in thermal expansion between the printed circuit board 10 and the metal chassis 20 in the solder 70 portion. Because the conductive pattern may be cut and the shielding characteristics may be impaired,
It is necessary to control the amount of solder to an appropriate range, and there is also a demand for a reduction in man-hours, so that the printed circuit board 10 is temporarily fixed to the metal chassis 20 and the back surface of the printed circuit board 10 is immersed in molten solder with the back surface facing downward. And the printed circuit board 10
And the metal chassis 20 and the feedthrough capacitor 40 are collectively soldered.

However, when the metal chassis 20 is immersed in the molten solder and then raised, the molten solder escapes and a sufficient amount cannot be secured, and the soldered portion may be broken during the temperature cycle test. For this reason, a sufficient amount of solder is secured by making the free ends of the electronic components with leads arranged on the periphery of the printed circuit board close to the metal chassis 20 so that the solder is easily accumulated. Forming work was required, which did not necessarily reduce man-hours.

Therefore, a structure as shown in FIGS. 5 to 7 has been proposed. 4 differs from FIG. 4 in that a cutout tongue piece 80 is formed in place of the elastic projection 60.
In the cut-out tongue piece 80, the base portion 80a is located on the front surface 10a side of the printed circuit board 10, the middle portion crosses the side peripheral surface of the printed circuit board 10, and the free end 80b is the back surface (the surface to be soldered and fixed) of the printed circuit board 10. 10b, the middle portion of the cut-out tongue 80 is bent inward of the metal chassis 20, and the free end 80b is projected onto the back surface 10b of the printed circuit board 10. The printed circuit board 10 is immersed in molten solder with the back surface 10b (the surface on which the conductive pattern 90 is formed) facing downward. At this time, the solder liquid level is よ り of the thickness of the printed circuit board 10 from the upper surface of the printed circuit board 10.
Immerse so that it is located about a degree above.

As a result, the solder does not crawl on the printed board 10 in the metal chassis 20 and the printed board 10
At the same time as the conductive pattern on the back surface is soldered to the lead (not shown) of the feedthrough capacitor, the cutout tongue 80 and the conductive pattern 90 are soldered. Thereafter, when the metal chassis 20 is pulled up from the molten solder, the cut-out tongue 8
0 is separated from the side wall of the metal chassis 20 downward, so that the cutout window 80c around the cutout tongue piece 80 is not clogged with solder. When the metal chassis 20 is completely pulled up from the molten solder in this way, the gap between the cut-out tongue 80 and the conductive pattern 90 on the printed circuit board 10 is fixed with an appropriate amount of solder as shown in FIG. By changing the amount of bending of the cut-out tongue 80, the amount of solder can be controlled arbitrarily, and the cut-out tongue 80 also has the effect of absorbing mechanical stress between the printed circuit board 10 and the metal chassis 20.

[0008]

However, the above-mentioned cutout tongue piece has an insufficient effect of absorbing mechanical stress when the area of soldering is made sufficiently large, and conversely, when the absorption of mechanical stress is sufficient, the cutout tongue piece becomes thin. There is a possibility that the width becomes too small and the soldering area becomes insufficient, so that the soldered portion is divided. In particular, as electronic devices have become smaller in recent years, it has become impossible to secure a cutout tongue piece of sufficient width from a metal chassis. In some cases, in order to further simplify the manufacturing process, it is desired that the soldering operation be completed only by the reflow process, which is the soldering process of the chip component. When the connection structure of the electronic device is rectangular and has a relatively large aspect ratio as shown in FIG. 8A, the expansion and contraction in the longitudinal direction becomes large, so the cutout tongue between the printed circuit board and the metal chassis having different thermal expansion coefficients. A large shear force is applied to the piece as shown in FIG. 3B, and the piece may be divided as shown in FIG.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a solder connection structure between a conductive pattern at a peripheral portion of a printed circuit board surrounded by a metal chassis and an inner peripheral surface of the metal chassis. The free end protrudes from the back surface of the printed circuit board, and at least a part of the free end is wider than the base thereof, and a recess is formed on the inner peripheral side of the metal chassis of the free end. And a cutout tongue having cutout windows on both sides at least on the base side from the back surface position of the printed circuit board. The cutout tongue is bent inward into the metal case, and the cutout tongue is bent into the metal chassis at the free end of the tongue. Provided is a solder connection structure in which a peripheral surface and the conductive pattern are fixed by soldering.

Further, the present invention provides a solder connection structure, wherein the recess formed on the inner peripheral surface side of the metal chassis at the free end is a groove. Further, the present invention provides a solder connection structure, wherein a groove is formed in an X-shape on the inner peripheral surface side of the metal chassis at the free end. Further, the present invention provides a solder connection structure, wherein a groove formed on the inner peripheral surface side of the metal chassis at the free end is perpendicular to the periphery of the printed circuit board.

Further, in order to enable the solder connection process to be completed only by the reflow process, a method of manufacturing a solder connection structure between the conductive pattern at the peripheral edge of the printed circuit board surrounded by the metal chassis and the inner peripheral surface of the metal chassis. In the metal chassis, the free end crosses the side peripheral surface of the printed circuit board and the free end protrudes from the back surface of the printed circuit board. At least a part of the free end is wider than its base, and the free end is A step of providing a cutout tongue having cutout windows on both sides at least on the base side from the back surface position of the printed circuit board; and forming the cutout tongue on a metal case. Bending inward; forming cream solder on the conductive pattern;
The solder, which has been reflowed and liquefied, is agglomerated by capillarity between the inner peripheral surface of the metal chassis at the free end of the tongue and the conductive pattern to form a metal shield at the free end of the tongue. A method for manufacturing a solder connection structure, comprising: a step of solder-connecting an inner peripheral surface side of the conductive pattern to the conductive pattern.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of the present invention, which differs from the conventional FIGS. 5 to 7 in that the base 8a of the cut-out tongue 8 is thin and the free end 8b is wide, and that This is the point where the portion 8d is provided. Since the free end portion 8b is wide and the recessed portion 8d is provided, even a small tongue piece of a small device has a groove with respect to the strength of soldering. The area is optimally large, the anchoring effect is large, and the base 8a is thin, so that the mechanical stress absorbing effect is sufficient, and the connection is impaired by the mechanical stress due to the difference in thermal expansion generated in the temperature cycle test and the like. Never.

As shown in FIGS. 2 (a) to 2 (d), various recesses 8d can be provided at the free end on the cut-out tongue piece 8, so that the free end and the solder can be better engaged. Even in the case of a small free end portion, a reliable solder connection becomes possible.
Further, by forming the recess 8d as a groove, the contact area with the solder on the free end can be substantially increased, and the groove is formed in an X-shape as shown in (a) and (d). By forming, the connection strength can be effectively provided with respect to the shear stress generated between the solder and the free end in each direction. Furthermore, when this groove is provided in the direction perpendicular to the side periphery of the printed circuit board as shown in (b), the rigidity of the cut-out tongue is large, and the force in the direction of the periphery of the printed circuit board which is vulnerable to the shearing force is reduced. Thus, the connection strength can be effectively obtained. The arrangement of the grooves may be as shown in FIG. Here, (e) is a perspective view showing the groove of the concave portion of (a), and the concave portions of other drawings are the same.

Furthermore, cutout windows 8 are provided on both sides of the base of the tongue.
c, immersion in the solder leaving a part of the base,
(To the extent that it does not rise to the surface of the printed circuit board), so that when the metal chassis 2 is lifted from the molten solder, the molten solder will fall down and at the same time also flow into the upper unimmersed portion to form a bridge that blocks the cutout window 8c. Never. Therefore, the stress absorbing action of the tongue piece is not impaired.

Further, it is needless to say that the present invention is not limited to the electronic tuner but can be generally applied to a case where a printed circuit board is connected to a metal chassis. In addition, according to the method of manufacturing a solder connection structure of the present invention, the printed circuit board 1 and the metal chassis 2 can be soldered by the reflow process. Connection with the metal chassis 2 becomes possible, and one step can be omitted as compared with the related art.

In this method, the cream solder for connecting the metal chassis 2 and the printed circuit board 1 can be formed simultaneously in the step of printing the solder for connecting chip components. In this reflow step, a small gap between the bent cut-out tongue piece 8 and the conductive pattern 9 on the printed circuit board 1 causes the liquefied solder to aggregate by capillary action, and
As shown in (1), the solder from the periphery of the tongue piece can also be collected to secure a sufficient amount of solder for the required connection strength, and the recessed portion 8d further promotes the action of the capillary phenomenon, and the above effect is obtained. It also has the function of reinforcing. In addition, as an arrangement of the groove as the recessed portion 8d formed in the tongue piece, one shown in FIG.

[0017]

As described above, according to the present invention, it is possible to realize a connection structure between a printed circuit board and a metal chassis having a sufficient strength even with a small electronic device. The connection structure can be made using a reflow soldering process. In addition, since the cut-out tongue temporarily fixes the printed circuit board and the wide free end of the cut-out tongue acts to secure an appropriate amount of solder and a soldering area, the proper amount of solder is used as in the past. Elaboration for securing is not required, and batch soldering can be easily performed.

The printed circuit board is connected to a cut-out tongue which is only a small part of the metal chassis, and since the base of the cut-out tongue is narrow, the cut-out tongue can be moved by a small distance in its width direction and in the longitudinal direction. Even if a difference in thermal expansion occurs between the printed circuit board and the metal chassis in a test or the like, the distortion is absorbed by the cut-out tongue, and the connection by the solder 7 is not impaired. In particular, a tongue piece having cutout windows on both sides at least on the base side from the back surface position of the printed circuit board realizes particularly strong connection strength against shear stress generated in the peripheral direction of the printed circuit board compared to the conventional one. Therefore, no solder bridge occurs during soldering, so that the tongue piece does not lose its strain absorbing effect.

[Brief description of the drawings]

FIG. 1 is a sectional side view of a main part of a connection structure showing an embodiment of the present invention.

FIG. 2 is an enlarged plan view of a main part of a connection structure of the present invention. (A) An X-shaped recessed groove. (B) A recessed groove provided in a direction perpendicular to the periphery of the printed circuit board. (C) A groove of the recessed part is formed around the printed circuit board. (D) An X-shaped groove in the recess (e) A perspective view of (a)

FIG. 3 is a view showing a capillary phenomenon of solder around a cut-out tongue piece.

FIG. 4 is a perspective view showing an example of a conventional connection structure.

FIG. 5 is a perspective view showing another example of a conventional connection structure.

FIG. 6 is a sectional view taken along the line AA of FIG. 5;

FIG. 7 is a perspective view of a main part of FIG. 1;

FIG. 8 is a view showing a force acting on a cut-out tongue piece and a metal chassis of a conventional connection structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed circuit board 2 Metal chassis 8 Cutout tongue piece 8d Depression (reinforcing means) 9 Conductive pattern

Claims (5)

[Claims] In a solder connection structure between a peripheral edge conductive pattern of a printed circuit board surrounded by a metal chassis and an inner peripheral surface of the metal chassis, the metal chassis crosses a side peripheral surface of the printed circuit board and has a free end. The free end protrudes from the back surface of the printed circuit board, at least a part of the free end is wider than its base, and reinforcing means is formed on the inner peripheral surface side of the metal chassis at the free end, and at least the back surface of the printed circuit board is provided. A cutout tongue having cutout windows on both sides is provided on the base side from the position. The cutout tongue is bent inward in the metal case, and the free end of the tongue is bent between the inner peripheral surface of the metal chassis and the conductive pattern. A solder connection structure characterized by being fixed by soldering. 2. The solder connection structure according to claim 1, wherein the reinforcing means formed on the inner peripheral side of the metal chassis at the free end is a groove of a concave portion. 3. The solder connection structure according to claim 2, wherein an X-shaped groove is formed on the inner peripheral side of the metal chassis at the free end. 4. The solder connection structure according to claim 2, wherein the groove formed on the inner peripheral surface side of the metal chassis at the free end is perpendicular to the periphery of the printed circuit board. 5. A method of manufacturing a solder connection structure between a conductive pattern at a peripheral portion of a printed circuit board surrounded by a metal chassis and an inner peripheral surface of the metal chassis, wherein the metal chassis traverses a side peripheral surface of the printed circuit board. The free end protrudes from the back surface of the printed circuit board, at least a part of the free end is wider than its base, and a recess is formed on the inner peripheral side of the metal chassis of the free end. Providing a cutout tongue having cutout windows on both sides at least on the base side from the back surface position of the printed circuit board; bending the cutout tongue inward into the metal case; and cleaning the conductive pattern on the conductive pattern. Forming the solder and reflowing the cream solder and liquefying the solder.
A step of agglomerating by capillary action between the inner peripheral surface of the metal chassis and the conductive pattern and soldering the inner peripheral surface of the metal chassis at the free end of the tongue to the conductive pattern. Method of manufacturing a solder connection structure.