JPH0997859A - Lead frame and its manufacturing method and method for manufacturing board for mounting electronic part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a board for mounting electronic parts for positively performing electrical conduction between a printed wiring board and a lead and can perform resin sealing without generating any void. SOLUTION: In a lead frame 1, a number of leads 10 are provided inside the frame. A lead tip part 11 in the lead 10 is a site which is joined to a printed wiring board for mounting electronic parts. The lead tip part 11 is bent in V shape from a base part 12 of the lead 10 toward a virtual extension line 120 which is extended in inner direction. A virtual extension line which is extended inside from the lead tip part 11 and the virtual extension line 120 extended from the base part 120 toward inside cross each other. The lead tip part 11 can be bent in V shape by press working.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a lead frame, a method of manufacturing the same, and a method of manufacturing an electronic component mounting board using the lead frame, and more particularly, to a lead tip portion of the lead frame and a through hole of the electronic component mounting board. Regarding joint structure.

[0002]

2. Description of the Related Art Conventionally, as a substrate for mounting electronic parts, FIG.
As shown in FIG.
There is one in which the lead tip portion 71 is soldered with a solder 59 (Japanese Patent Laid-Open No. 5-121626). The printed wiring board 3 and the lead tips 71 around the printed wiring board 3 are covered with a sealing resin 91 after the electronic components are mounted on the printed wiring board 3.

Next, in manufacturing the electronic component mounting substrate 9, as shown in FIG. 8, the step bending portion 7 for absorbing stress at the time of joining is formed on the lead tip portion 71 of the lead 70.
18 is provided. On the other hand, the printed wiring board 3 is prepared in which the through hole 20 is provided in the peripheral portion of the insulating substrate 2 and the conductor circuit 55 is provided inside thereof. The inner wall of the through hole 20 is covered with a metal plating film 51. The surface of the conductor circuit 55 is covered with the solder resist film 6. Next, the adhesive 8 is placed on the peripheral portion of the printed wiring board 3.
Next, the lead tip portion 71 of the lead 70 is arranged above the through hole 20.

Next, as shown in FIG. 9, the lead tip 71 of the lead 70 is pressed against the adhesive 8 and heated. As a result, the adhesive 8 is hardened and the leads 70 are bonded and fixed to the printed wiring board 3. Next, Fig. 1
As shown in 0, the melted solder 59 is introduced into the through hole from below the through hole 20, and the through hole 20 and the lead tip portion 71 are soldered and joined. As a result, the electronic component mounting board 9 in which the lead tips 71 are soldered to the printed wiring board 3 is obtained.

[0005]

However, in the above-described conventional method for manufacturing an electronic component mounting substrate, the lead tip 71 may jump upward. When the lead tip 71 is bonded to the printed wiring board 3, the lead tip 71 floats upward as shown in FIG. 10, and a gap is formed between the lead tip 71 and the through hole 20. Therefore, an electrical connection failure may occur between the through hole 20 and the lead 70.

The through hole 20 and the lead tip 7
If there is a gap between 1 and 1, as shown in FIG.
When the printed wiring board 3 is sealed with the sealing resin 91, voids may occur above the through holes 20.

Further, the applicant of the present application is
We have developed a technology to enhance the bondability of the two by elastically deforming them into a concave shape with respect to the through hole 20, and filed a prior application (Japanese Patent Application No. 6-88020). However, this technology
Since the lead does not have the step bend portion, it may not be possible to absorb the stress generated at the lead tip during joining.

In view of the above conventional problems, the present invention mounts an electronic component capable of surely performing electrical conduction between a printed wiring board and a lead and resin-sealing without generating a void. A method of manufacturing a substrate for use, a lead frame used in this manufacturing method, and a method of manufacturing the same are provided.

[0009]

According to the present invention, a large number of leads are arranged inside a frame, and the lead tips provided at the inner tips of the leads are joined to a printed wiring board for mounting electronic parts, while In a lead frame in which the base of the lead projects outward from the printed wiring board, the tip of the lead bends in a V shape in the direction of a virtual extension line extending inward from the base of the lead. A lead frame for mounting electronic parts, characterized by being formed.

The lead is connected to a conductor pattern such as a through hole, a conductor circuit, or a pad formed on the printed wiring board, and plays a role of taking out an electric signal from the outside or taking in an electric signal from the printed wiring board. The lead tip portion of the lead is a portion joined to the printed wiring board.

Next, the operation of the lead frame will be described. As shown in FIG. 4, the lead tip portion of the lead frame is bent in a V shape in the direction of an imaginary extension line 120 extending inward from the base portion 12 of the lead (that is, the lead tip portion direction). Therefore, when the lead frame is arranged on the surface of the printed wiring board, the lead tips are inclined downward.

Therefore, when the printed wiring board is arranged under the lead tip when the lead tip is joined, the lead tip comes into close contact with the surface of the printed wiring board and presses the printed wiring board. Therefore, unlike the conventional case, the tip of the lead does not bounce upward, and a gap does not occur between the printed wiring board and the tip of the lead. Therefore, even when the surface of the printed wiring board is resin-sealed, the entire surface of the printed wiring board can be completely sealed without generating voids.

Next, at the tip of the lead, a virtual extension line extending inward from the tip of the lead and a virtual extension line extending inward from the base intersect at an angle of 0.3 to 5 degrees. It is preferable that it is bent so that it does (see FIG. 4). If the angle is less than 0.3 degrees, the tip of the lead may jump upward with respect to the printed wiring board. On the other hand, if the angle exceeds 5 degrees, the contact area between the lead tip and the printed wiring board decreases, and the bonding strength may decrease. The lead tips can be joined to the through holes of the printed wiring board or the conductor circuits by soldering, for example.

Next, as a method of manufacturing the lead frame, for example, a large number of leads are arranged inside the frame, and the tip ends of the leads inside the leads are joined to a printed wiring board for mounting electronic components. On the other hand, in the method of manufacturing a lead frame in which the base of the lead is projected to the outside of the printed wiring board, first, the metal plate is provided with a frame, a large number of leads provided inside the frame, and the leads. A connecting bar that connects adjacent leads at the inner tip is formed, and then the metal plate is pressed to form a virtual extension line that extends the lead tip inward from the base of the lead. Leads for mounting electronic parts, characterized in that they are bent in a V shape in the direction, and then the connecting bar is cut to separate each lead from an adjacent lead. There is a method of manufacturing the frame.

In the above-mentioned manufacturing method, a connecting bar provided for connecting between adjacent leads is formed at the lead tips of a large number of leads. The connecting bar suppresses the positional deviation of the leads in the plane direction during press working. Therefore, it is possible to bend a plurality of lead tips arranged in parallel in the same direction.

Further, it is preferable that at least the tip of the lead is heated after being bent in a V shape. The reason is that the stress in the bent portion of the V-shaped lead tip portion is relaxed by heating, so that the V-shaped shape can be maintained for a long period of time. The heating temperature of the lead tip depends on the material of the lead frame, but is preferably around 400 ° C. when the lead frame is made of a copper alloy, for example.

Next, as a method of manufacturing an electronic component mounting substrate using the above lead frame, for example, a large number of leads are arranged inside the frame, and the lead tips inside the leads are Prepare a lead frame that is bent in a V shape in the direction of a virtual extension line that extends inward from the base of, and then the lead tips are located above the through holes of the printed wiring board. An electronic component mounting device characterized in that the lead frame is arranged above the printed wiring board so that the base portion projects outward from the printed wiring board, and then the lead tip portion and the through hole are joined by soldering. There is a method of manufacturing a substrate for use.

In the above-mentioned manufacturing method, since the lead tips of the leads press the printed wiring board,
The tip of the lead comes into close contact with the through hole. Therefore, a good electrical connection between the lead and the through hole can be secured. In soldering the lead tip and the through hole, for example, there is a method in which a printed wiring board is placed on the upper surface of the solder bath and solder is raised from below the through hole to join the two.

Before soldering the lead tip to the through hole, it is preferable to fix the lead tip and its vicinity to the surface of the printed wiring board with an adhesive.
As a result, it is possible to prevent the positional deviation from occurring between the lead frame and the printed wiring board. Also, the joint reliability between the lead tip and the through hole is improved.

[0020]

DETAILED DESCRIPTION OF THE INVENTION A lead frame according to an embodiment of the present invention will be described with reference to FIGS. The lead frame of this example is, as shown in FIG.
A large number of leads 10 are arranged on the inner side of 9. Lead end portions 11 located inside the large number of leads 10 are portions joined to the printed wiring board 3. Lead tip 11
As shown in FIG. 4, is bent in a dogleg shape in the direction of a virtual extension line 120 extending inward from the base portion 12 of the lead 10. The lead tip portion 11 is a portion shown by a hatched area in FIG.

The lead tip portion 11 has an imaginary extension line 110 extending inward from the lead tip portion 11 and a virtual extension line 120 extending inward from the base portion 0.3 to 5.
It is bent in a V shape so that it intersects at an angle α of degrees.
The distance h between the virtual extension line 120 of the base portion 12 and the tip 112 of the lead tip 11 is shorter than the distance H between the virtual extension line 120 and the bent portion 111 of the lead tip 11, and the difference ΔH (H−h ) Is 5 to 260 μm. The length L from the bent portion 111 to the tip 112 of the lead tip 11 is 1 to 3 mm.

As shown in FIG. 5, the base portion 12 is a portion extending outward from the lead tip portion 11 in the plane direction of the lead frame 1. One end of the base 12 has a lead tip 11
And the other end is connected to the frame 19. A jig hole 17 for fixing the lead frame 1 is formed in the frame 19. Note that the base 12 of the lead 10 retains the shape of the lead 10, and therefore, as shown in FIG. 5, it is preferable to provide a holding bar 101 for connecting between the adjacent bases 12.

Next, a method of manufacturing the lead frame will be described. First, as shown in FIG. 6, etching is performed on a metal plate to connect a frame, a large number of leads provided inside the frame, and lead ends provided at inner ends of the large numbers of leads. Forming a bar 100.

Next, the lead 10 is pressed downward along the dotted line A shown in FIG. 6 by metal pressing. On the other hand, the lead 10 is pressed upward along the dotted line B in FIG. As a result, as shown in FIG. 4 and FIG.
The bending point B located in the outer direction of 0 is the lead tip 11
And the base portion 12 as a boundary. On the other hand, at the bending point A located inward of the lead 10, the lead tip 11 is formed in a V shape to form the bending portion 111. The bending degree of the bending points A and B is, as described above, the lead tip 1
1 is a virtual extension line 12 extending inward from the base 12.
The extent is toward 0.

Then, the metal plate is heated at 400.degree. This relieves the internal stress of the lead that occurs during bending. After that, by pressing, the connecting bar 100
Is cut and each lead 10 is separated. As a result, the lead frame 1 is obtained.

Next, a method of manufacturing an electronic component mounting board using the lead frame will be described. First,
As shown in FIGS. 1 and 5, the through hole 2 is formed in the insulating substrate 2.
0 is bored, and a metal plating film 51 is applied inside. Further, a conductor circuit 55 and a mounting portion 50 for mounting electronic components are formed on the surface of the insulating substrate 2. Further, the surface of the insulating substrate 2 is covered with the solder resist film 6 while leaving the periphery of the through hole 20. Thereby, the printed wiring board 3 is obtained.

Next, as shown in FIG.
The adhesive 8 is applied to the vicinity of the outer peripheral portion of 0. A thermosetting resin is used as the adhesive 8. Then, the lead frame 1
The lead frame 1 and the printed wiring board 3 are aligned so that the lead tip 11 of the above is located above the through hole 20.

Then, as shown in FIG. 2, the lead frame 1 is lowered to attach the lead tip 11 to the through hole 2.
Place on top of 0. As a result, the lead frame 1 is bonded and fixed to the printed wiring board 3 with the adhesive 8. Next, as shown in FIG. 3, the printed wiring board 3 is placed on the upper surface of the solder bath, the molten solder 59 is filled from below the through hole 20, and the through hole 20 and the lead tip 11 are connected by the solder 59. To join. As a result, the electronic component mounting board 9 is obtained.

After that, the electronic component mounting board 9 is mounted with an electronic component on the mother board after resin sealing. That is, electronic parts are mounted on the mounting portion 50 of the printed wiring board 3. Then, the printed wiring board 3 is sealed with a resin 9 for sealing.
The resin is sealed with 1 (see FIG. 7). Further, the frame 19 of the lead frame 1 is cut and removed. And lead 1
The other end of the base 12 at 0 is soldered to the pad of the motherboard.

Next, the function and effect of this example will be described.
In the lead frame 1 of this example, as shown in FIG.
It is bent in a dogleg shape in the direction of an imaginary extension line 120 extending inward from the base portion 12 at 0 (that is, toward the lead tip portion 11). Therefore, when the lead frame 1 is arranged on the surface of the printed wiring board 3, the lead tip portion 11 is inclined downward (FIG. 1).

Therefore, when the printed wiring board 3 is arranged under the lead tip portion when the lead tip portion 11 is joined, the lead tip portion 11 adheres to the surface of the printed wiring board 3 and the printed wiring board 3 is attached. Hold down. For this reason,
Unlike the conventional case, the lead tip 11 does not bounce upward, and no gap is generated between the printed wiring board 3 and the lead tip 11. Therefore, even when the surface of the printed wiring board 3 is resin-sealed (see FIG. 7), the entire surface of the printed wiring board 3 can be completely sealed without generating voids.

Further, in manufacturing the lead frame 1, as shown in FIG. 6, a connecting bar 100 for connecting between the adjacent leads 10 is formed at the lead tip 11 of the lead 10. The connecting bar 100 suppresses positional deviation of the leads in the plane direction during press working. Therefore, it is possible to bend a plurality of lead tips 11 arranged in parallel in the same direction.

In the method of manufacturing the electronic component mounting board 9, the lead tip portion 11 presses the through hole 20 of the printed wiring board 3, so that the through hole 2 is formed.
Stick to 0. Therefore, good electrical connection between the lead 10 and the through hole 20 can be ensured.

[0034]

According to the present invention, there is provided an electronic component mounting substrate which can ensure electrical conduction between the printed wiring board and the leads and can be resin-sealed without generating voids. A manufacturing method, a lead frame used in this manufacturing method, and a manufacturing method thereof can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view before joining a lead frame and a printed wiring board in an embodiment example.

FIG. 2 shows a lead frame bonded in the embodiment,
Sectional explanatory drawing of the fixed printed wiring board.

FIG. 3 is an explanatory cross-sectional view of a board for mounting electronic components, in which lead tips are solder-bonded to through holes of a printed wiring board in the embodiment.

FIG. 4 is a front view of the lead and its vicinity in the lead according to the embodiment.

FIG. 5 is an explanatory plan view of the lead frame and the printed wiring board before joining in the embodiment.

FIG. 6 is an explanatory view of a lead frame manufacturing method in the embodiment.

FIG. 7 is an explanatory cross-sectional view of a resin-sealed electronic component mounting substrate in a conventional example.

FIG. 8 is an explanatory cross-sectional view of a conventional example before joining a lead frame and a printed wiring board.

FIG. 9 is a cross-sectional explanatory view of a printed wiring board to which a lead frame is adhered and fixed in a conventional example.

FIG. 10 is a cross-sectional explanatory view of a board for mounting electronic parts, in which a lead tip is soldered to a through hole of a printed wiring board in a conventional example.

[Explanation of symbols]

 1. . . Lead frame, 10. . . Lead, 11. . . Lead tip, 12. . . Base, 120. . . Virtual extension line, 20. . . Through hole, 3. . . Printed wiring board, 59. . . Solder, 8. . . Adhesive, 9. . . Electronic component mounting board,

Claims (5)

[Claims] 1. A large number of leads are arranged inside a frame, and the lead tips provided at the inner tips of the leads are joined to a printed wiring board for mounting electronic parts, while the bases of the leads are connected to each other. In the lead frame projecting outward from the printed wiring board, the lead tips are bent in a V shape in the direction of a virtual extension line extending inward from the base of the lead. Characteristic lead frame for mounting electronic parts. 2. The lead tip portion according to claim 1, wherein a virtual extension line extending inward from the lead tip portion and a virtual extension line extending inward from the base portion are in a range of 0.3 to 5 A lead frame for mounting electronic components, which is bent so as to intersect at an angle of degrees. 3. A large number of leads are arranged inside a frame, and lead ends inside the leads are joined to a printed wiring board for mounting electronic parts, while the bases of the leads are connected to the printed wiring board. In a method of manufacturing a lead frame that projects outward from a plate, first, a frame, a number of leads provided inside the frame, and a lead that is adjacent to the inner end of the frame are connected to a metal plate. A connecting bar is formed, and then the metal plate is pressed to bend the lead tip into a dogleg shape in the direction of a virtual extension line extending inward from the base of the lead, Thereafter, the connecting bar is cut to separate each lead from an adjacent lead, and a method for manufacturing a lead frame for mounting an electronic component. 4. The method of manufacturing a lead frame for mounting an electronic component according to claim 3, wherein at least the lead tip is heated after the lead tip is bent in a V shape. 5. A large number of leads are arranged inside a frame, and the lead tips inside the leads are V-shaped in the direction of a virtual extension line extending inward from the base of the lead. A lead frame is formed by bending the lead frame, and then the lead frame is printed wiring so that the lead ends are located above the through holes of the printed wiring board and the base portion is projected outward from the printed wiring board. A method of manufacturing a board for mounting electronic parts, characterized in that the board is placed on the upper side of the plate, and then the lead tip and the through hole are joined by soldering.