JP2000100508A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board, allowing certain fitting and holding of a conductor pin without damage of its via hole with a high joining strength, and allowing a high density mounting of the conductor pins. SOLUTION: A head part 11 of a conductor pin 1 having a leg part 13 is press fitted into a via hole 6 of a printed wiring board. The head part 11 is formed with projecting portions 111 projecting from its sidewall and recessed portions 112 recessed from the projecting portions 111 toward a central axis of the via hole 6. An upper opening part of the via hole 6 is blocked with a metal pad 50. The head part 11 of the conductor pin 1 is press fitted into the via hole 6 from a lower opening part side of the via hole 6 so that the projecting portions 111 are fixed to an inner wall of the via hole 6 by caulking. The via hole 6 and the head part 11 of the conductor pin 1 are joined together with solder 2 flowing in gaps 60 formed between the inner wall of the via hole 6 and the recessed portions 112.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board, and more particularly, to a joint structure between a conductor pin and a via hole.

[0002]

2. Description of the Related Art As shown in FIG.
An insulating substrate 90, a large number of via holes 91 formed in the insulating substrate 90, a concave electronic component mounting portion 95 provided near the center of the insulating substrate 90, and a projecting frame-shaped dam 98 provided therearound. Become. Reference numeral 93 denotes a conductor circuit, 9
4 is a land. The head 921 of the conductor pin 92 is fitted into the via hole 91, and the head 921 and the plating layer 911 of the via hole 91 are electrically connected. The conductor pin 92 has a flange 922 and a leg 923. The conductor pins 92 inserted at the four corners of the insulating substrate 90
Has a lower collar 924 as well.

Further, between the head 921 of the conductor pin 92 and the via hole 91, soldering is performed with the solder 8 in order to secure electrical connection between the conductor pin 92 and the via hole 91 and mechanical strength therebetween. ing. This soldering
For example, it is performed by a reflow method in which the molten solder 8 flows in a direction opposite to the fitting direction of the conductor pins 92.

That is, as shown in FIG. 5, a head 921 of a conductor pin 92 is inserted into a via hole 91 of an insulating substrate 90, and
A paste solder 89 composed of solder particles and a flux is placed thereon, and then heated and melted. As a result, the molten solder 8 flows down into the joining gap between the via hole 91 and the head 921, and joins the two (FIG. 4).
The printed wiring board 9 is provided with an electronic component mounting portion 9.
5 is a face-down type in which conductor pins are fitted from the same side as 5.

[0005]

However, as described above, when the head 921 of the conductor pin 92 is inserted into the via hole 91, if the diameter of the head is small, the via hole 91
Although the head 921 is easily inserted into the inside, the conductor pins 92 may fall off before the soldering step. On the other hand, when the diameter of the head 921 is increased in order to firmly fit the head 921, the flange 922 is
The inner wall of the through-hole 91 is strongly pressed at the time of insertion, and the inner wall of the through-hole 91 is strongly pressed, causing damage such as a crack on the inner wall of the through-hole or peeling of plating covering the inner wall of the through-hole.

[0006] The conductor pins not only serve as support members for fixing the printed wiring board to other members, but also serve as support members.
It also plays a role as an electrical transmission path. Therefore, the bonding strength of the conductor pin to the via hole is required. A method of forming a via hole using a laser is being developed. According to the laser, a via hole having a small diameter can be formed, which is suitable for high-density mounting.

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to securely insert and hold a conductor pin without damaging a via hole, to achieve a high bonding strength to a via hole and to realize a printed wiring which can realize high-density mounting. It is intended to provide a board.

[0008]

The present invention provides a printed wiring board comprising an insulating substrate provided with a conductor circuit and a via hole, and a conductor pin having a head press-fitted into the via hole and having a leg. The head has a protruding portion protruding from the side wall thereof and a recessed portion which is recessed in the direction of the center axis of the via hole from the protruding portion, and the upper opening of the via hole is closed by a metal pad. A printed wiring, wherein a head of the conductor pin is fixed to the inner wall of the via hole by caulking, and a metal material is connected between the via hole and the head of the conductor pin. It is a board.

The most characteristic features of the present invention are that the upper opening of the via hole is covered with a metal pad, and that the head of the conductor pin has a protrusion protruding from the side wall thereof, and the protrusion is formed in the via hole. That is, it is caulked and fixed to the inner wall.

The operation and effect of the present invention will be described.
The head of the conductor pin has a protrusion on its side wall. When the head of the conductor pin is pressed into the via hole, the protrusion is fixed by caulking while the protrusion slightly presses the inner wall of the via hole. Therefore, the head can be firmly held in the via hole, and the conductor pin does not fall off.

On the other hand, the head of the conductor pin has a recess that is recessed in the direction of the center axis of the head rather than the protrusion. When the head of the conductor pin is inserted into the via hole, a gap is generated between the recess of the head and the inner wall of the via hole. Therefore, the inner wall of the via hole in which the recessed portion is fitted does not press.
Therefore, the distortion of the inner wall of the via hole caused by the pressing by the protruding portion is eliminated by the inner wall of the via hole into which the recess is inserted. Therefore, the inner wall of the via hole is not damaged.

The gap between the inner wall of the via hole and the depression forms a flow path for the molten metal material. for that reason,
Through such a flow path, the molten metal material flows into the via hole from the lower opening of the via hole. And
The tip of the molten metal material contacts a metal pad that covers the upper opening of the via hole. Therefore, the metal material is bonded not only to the side wall of the via hole but also to the metal pad that covers the upper opening. Therefore, the conductor pins are firmly joined to the via holes.

As described above, according to the present invention, the conductor pin can be securely inserted and held without damaging the via hole, and the bonding strength to the via hole is high.
In addition, high-density mounting can be realized.

Next, the details of the present invention will be described. The protruding portion of the conductor pin head is press-fitted into the via hole and caulked and fixed to the inner wall of the via hole. It is preferable that the protruding portion protrudes from the inner wall of the via hole by a protruding amount C of 0 to 50 μm (see FIG. 3). Thus, the inner wall of the via hole can be securely caulked and fixed to the inner wall without damaging the inner wall. On the other hand, 0
If it is less than μm, the conductor pins may fall off. If it exceeds 50 μm, the press-in force of the conductor pin becomes excessively large, which may damage the inner wall of the via hole.

The recess at the head of the conductor pin is recessed in the direction of the center axis of the via hole from the protrusion. There is a slight gap between the recess and the inner wall of the via hole, and the metal material is filled into the via hole through the gap. The maximum gap amount D of the gap between the depression and the inner wall of the via hole is 1 to 50.
μm (see FIG. 3). If the thickness is less than 1 μm, the metal material may not flow smoothly and a metal-unfilled portion may remain in the via hole. Also, 5
If it exceeds 0 μm, the strength of the head of the conductor pin may decrease. Note that each of the protruding portion and the recessed portion may be provided at only one location on the head of the conductor pin, or may be provided at a plurality of locations.

The metal material flowing into the via hole is preferably solder. This is because fusion bonding can be performed at a relatively low temperature and high bonding strength can be obtained. Also,
In addition, a material having electrical conductivity such as a conductive resin and a soft solder can be used.

The cross-sectional structure of the head of the conductor pin is, for example, as shown in FIG. 3, a flat plate shape (FIG. 3A), a rectangular shape (FIG. 3B), and a three arrow shape (FIG. c)), a cross shape (FIG. 3D), a flower shape (FIG. 3E), an L-shape (f), and the like. In such a structure, the longest portion is the protruding portion 111 of the conductor pin head 11, and the shortest portion is the concave portion 112. A gap 60 is provided between the recess 112 and the inner wall of the via hole 6.

The head of the conductor pin preferably has a top projecting from the upper opening of the via hole.
Thus, the conductor pins can be smoothly fitted into the via holes.

It is preferable that the conductor pin has a flange between the head and the leg, the flange being brought into contact with an insulating substrate. As a result, the conductor pin can be securely joined to the lower opening of the via hole with the metal material.

The printed wiring board includes an insulating resin for covering the insulating substrate in a state where the joint between the via hole and the conductor pin is opened, and a fixing resin provided between the insulating resin and the conductor pin. And the fixing resin has
It is preferable to form a coating that continuously contacts the insulating resin from the leg of the conductor pin via the metal material.

The bonding strength between the fixing resin and the insulating resin is high. For this reason, the fixing resin is solidified by melting and solidifying, so that the wall surface of the insulating resin and the conductive pin are in contact with each other, so that the conductive pin is extremely strongly bonded to the insulating resin around the lower opening of the via hole Is done.

As the fixing resin, an epoxy resin, a polyimide resin, a bismaleimide triazine resin or the like can be used. Further, the same material as the insulating resin may be used. As the insulating resin, for example, epoxy, polyimide, bismaleimide triazine and the like can be used. Further, a material used for a general solder resist may be used.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A printed wiring board according to an embodiment of the present invention will be described with reference to FIGS. The printed wiring board of this example is
As shown in FIG. 1, an insulating substrate 7 provided with a conductor circuit 5 and a via hole 6 and a conductor pin 1 having a head portion 11 pressed into the via hole 6 and having a leg portion 13 are provided.

As shown in FIG. 3A, the head 11 of the conductor pin 1 has a flat plate structure, and has a protruding portion 111 protruding from a side wall thereof and a recess in the center axis direction of the via hole 6 with respect to the protruding portion 111. And a depression 112.

The inner wall of the via hole 6 is covered with a metal plating film 65 made of copper. The upper opening of the via hole 6 is closed by a metal pad 50. The head 11 of the conductor pin 1 is press-fitted from the lower opening of the via hole 6, and the protrusion 111 of the conductor pin 1 is
It is caulked and fixed to the inner wall. The via hole 6 and the head 11 of the conductor pin 1 are joined by the solder 2 flowing through the gap 60 between the inner wall of the via hole 6 and the recess 112.

The head 11 of the conductor pin 1 has a top 10 projecting from the upper opening of the via hole 6. The conductor pin 1 has a flange portion 12 abutting on the insulating substrate 7 between the head portion 11 and the leg portion 13.

The printed wiring board is provided between the insulating resin 4 and the conductive pin 1 with the insulating resin 4 covering the insulating substrate 5 with the joint between the via hole 6 and the conductive pin 1 opened. And a fixing resin 3. The fixing resin 3 forms a coating that continuously contacts the insulating resin 4 from the leg 13 of the conductor pin 1 via the solder 2. Insulating resin 4
Is the same material as general solder resist, for example,
Epoxy resin or the like is used. The same material as the insulating resin 4 is used for the fixing resin 3.

The soldering of the conductor pins to the via holes is performed by, for example, reflow of a solder paste, reflow of a solder ring, and dipping in molten solder. Next, a ring-shaped semi-cured fixing resin 3 is inserted from the leg 13 of the conductor pin 1. The fixing resin 3 is heated. Then, the fixing resin 3 is melted, and the solder 2 is transferred from the leg 13 of the conductor pin 1.
Along with the surrounding insulating resin 4. By cooling in this state, the fixing resin 4 is hardened, and the conductor pins 1 are joined to the insulating resin 4.

The printed wiring board of the present embodiment has a concave mounting portion 78 for mounting the electronic component 8. It is a face-up type in which the conductor pins 1 are press-fitted from the side opposite to the opening side of the mounting portion 78. It should be noted that a face dyne type may be used as in the conventional example. The electronic component 8 and the conductor circuit 5 are electrically connected by a bonding wire 81. As the insulating substrate 7, a glass polyimide substrate, a glass bismaleimide triazine substrate, or the like is used.

Next, the operation and effect of this embodiment will be described. When the protrusion 111 provided on the head 11 of the conductor pin 1 is press-fitted into the via hole 6, the protrusion 111 is caulked and fixed while slightly pressing the inner wall of the via hole 6. Therefore, the head 11 can be firmly held in the via hole 6, and the conductor pin 1 does not fall off.

On the other hand, the recess 112 provided in the head 11 of the conductor pin 1 forms a gap 60 between the via hole 6 and the inner wall of the via hole 6 when pressed into the via hole 6. for that reason,
The recess 112 does not press the inner wall of the via hole 6 at the time of press-fitting the conductor pin. Therefore, the distortion of the inner wall of the via hole 6 caused by the press-fitting by the protruding portion 111
2 is eliminated by the inner wall of the via hole in which the fitting 2 is inserted. Therefore,
The inner wall of the via hole is not damaged.

The inner wall of the via hole 6 and the recess 112
Is a flow path for the molten solder 2. Therefore, the molten solder 2 passes through the solder flow path.
It flows into the via hole 6 from the lower opening of the via hole 6. Then, the tip of the molten solder 2 contacts the metal pad 50 that covers the upper opening of the via hole 6. Therefore, the solder 2 is bonded not only to the side wall of the via hole 6 but also to the metal pad 50 that covers the upper opening. Therefore, the conductor pin 1 is firmly joined to the via hole 6.

The fixing resin 3 is melted and solidified and continuously contacts the wall surface 40 of the insulating resin 4 around the lower opening of the via hole 6 and the conductor pin 1. Therefore, stress concentration does not occur at the discontinuous contact portion, and no crack or the like is generated. Therefore, the bonding strength between the fixing resin 3 and the insulating resin 4 is high. Therefore, conductor pin 1
Is very strongly bonded to the insulating resin 4.

[0034]

According to the present invention, there is provided a printed wiring board capable of securely inserting and holding a conductor pin without damaging a via hole, having high bonding strength to the via hole, and realizing high-density mounting. can do.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view taken along line AA of FIG. 3A, showing a via hole in which a conductor pin is press-fitted and joined, and FIG. Sectional view (b) of FIG.

FIG. 2 is a cross-sectional view of the printed wiring board according to the first embodiment.

FIG. 3 is a cross-sectional view of the head of the conductor pin of the present invention (a) to
(F).

FIG. 4 is a cross-sectional view of a printed wiring board in a conventional example.

FIG. 5 is an explanatory diagram of a flow of solder into a via hole in a conventional example.

[Explanation of symbols]

 1. . . 9. Conductor pin, . . Top, 11. . . Head, 111. . . Protrusions, 112. . . Recessed part, 12. . . Tsubame, 13. . . Leg, 2. . . 2. solder, . . Fixing resin, 4. . . 4. Insulating resin, . . Conductor circuit, 60. . . Gap, 65. . . 6. metal plating film; . . Insulating substrate, 78. . . 7. mounting part, . . Electronic components,

Continued on the front page (72) Inventor Naoto Ishida 3-200, Kawamacho, Ogaki-shi, Gifu F-term in Kawama Plant of IBIDEN Corporation (Reference) 5E077 BB12 CC21 DD01 DD12 EE09 FF12 GG10 GG29 JJ21 5E336 AA01 AA08 AA09 AA16 BB02 BC01 BC15 BC25 BC34 BC36 CC02 CC23 DD02 DD16 EE01 EE14 GG30

Claims (4)

[Claims] 1. A printed wiring board comprising: an insulating substrate provided with a conductor circuit and a via hole; and a conductor pin having a head press-fitted into the via hole and having legs. A protrusion protruding from the side wall, and a recess recessed in the direction of the center axis of the via hole from the protrusion, the via hole having an upper opening closed by a metal pad; A printed wiring board, characterized in that the head is fixed by caulking to the inner wall of a via hole, and the via hole and the head of the conductor pin are joined by a metal material. 2. The printed wiring board according to claim 1, wherein the head of the conductive pin has a top projecting from an upper opening of the via hole. 3. The printed wiring board according to claim 1, wherein the conductor pin has a flange between the head and the leg, the flange being in contact with an insulating substrate. 4. The printed wiring board according to claim 1, wherein the printed wiring board includes an insulating resin for covering an insulating substrate in a state where a joint between the via hole and the conductive pin is opened, and an insulating resin between the insulating resin and the conductive pin. And a coating that is in continuous contact with the insulating resin from the legs of the conductor pin via the metal material through the fixing resin. A printed wiring board characterized by the above.