JP2002009404A - Printed wiring board with heat sink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of voids in sealing resin and avoid generation of imperfect connection and deterioration of sealing strength, in a printed wiring board with a heat sink, which is used for a driver module of a plasma display panel or the like. SOLUTION: Elements 2 are bonded to the surface of a heat sink 3, and the heat sink is stuck on the back of a printed wiring board 1 by using an adhesive sheet 4. On the back of the printed wiring board 1, a ground pattern is continuously formed surrounding the elements 2. On he adhesive sheet 4, notches 41 which stretch from the vicinity of the ground pattern as far as outside end of the adhesive sheet 4 are formed. As a result, air enclosed in the periphery of the ground pattern does not enter the inside of the ground pattern when heat sink 3 is stuck on the printed wiring board 1.

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 with a heat sink, and more particularly to an improvement in a resin sealing portion of the printed wiring board with a heat sink.

[0002]

2. Description of the Related Art For example, a driver module (drive integrated circuit) used for a plasma display panel (discharge display panel) includes a large number of elements (chips, for example, integrated circuits).
A printed wiring board (printed circuit board) on which is mounted is used. In this type of printed wiring board with a heat sink, a structure is used in which a heat sink made of a material having good thermal conductivity, for example, aluminum is attached in order to efficiently radiate heat generated from these elements during use. .

[0003] Such a printed wiring board with a heat sink is
Specifically, for example, it has the following structure. That is, the chip is fixed to one surface of the heat sink with a conductive adhesive or the like, and the printed wiring board is fixed around the chip. Next, the element is electrically connected to the printed wiring board by wire bonding or the like. Thereafter, in order to protect the element and the bonding, a liquid resin is applied to the element and its peripheral portion, and the resin is sealed by heating and curing.

Here, in the conventional structure, a conductive pattern, for example, a U-shaped ground pattern is formed on the printed wiring board, and the printed wiring board is placed in a state where the ground pattern is opposed to the one surface. Is fixed to the heat sink. For fixing the printed wiring board to the heat radiating plate, a method of attaching the printed wiring board via an adhesive sheet (adhesive sheet) is usually used because of simplicity of the work. That is, the surface on the ground pattern side of the printed wiring board is bonded to the heat sink via the adhesive sheet.

[0005]

However, this printed wiring board with a heat sink has the following problems.

That is, when the printed wiring board is bonded to the heat sink through the adhesive sheet as described above, the ground pattern formed on the printed wiring board is slightly projected from the surface of the printed wiring board. Therefore, in the peripheral portion of the ground pattern, a gas of the working atmosphere, for example, air is trapped between the printed wiring board and the adhesive sheet.

When the liquid resin is applied in the next step and sealed by heating and curing, the trapped air expands due to heating, and this air flows from the opening of the U-shaped ground pattern to the ground pattern. Get inside. As a result, air is confined in the sealing resin by air bubbles, and the air bubbles become voids in the sealing resin.
Will be. As a result, stress is applied to the wires inside the resin sealing portion, which may cause poor connection or poor conductivity. In addition, there has been a problem that sealing is incomplete and sealing strength is reduced.

In view of such circumstances, the present invention prevents the occurrence of voids in the sealing resin during the heating and curing of the sealing resin, thereby suppressing the occurrence of connection failure and the like and the reduction in sealing strength. It is an object of the present invention to provide a printed wiring board with a heat sink, which can perform the above.

[0009]

A printed wiring board with a heat radiating plate according to the present invention has a predetermined element fixed to one surface of the heat radiating plate and a conductive pattern arranged opposite to the one surface. The printed wiring board provided is bonded to the periphery of the element via an adhesive sheet, the element is electrically connected to the printed wiring board, and the element and a part of the printed wiring board adjacent to the element are connected. In a printed wiring board with a heat sink that is sealed with resin,
The conductive pattern is formed continuously on the outer periphery of the element. Here, examples of the conductive pattern include a signal pattern in addition to a ground pattern.

By adopting such a configuration, the gas (eg, air) of the working atmosphere confined around the conductive pattern when the heat sink is bonded to the printed wiring board with the adhesive sheet is continuously formed. The conductive pattern prevents the conductive pattern from entering the inside of the conductive pattern during expansion during resin sealing.

The adhesive sheet is formed by forming a notch extending from the vicinity of the conductive pattern to the outer end of the adhesive sheet. According to this configuration, since the conductive pattern communicates with the working atmosphere outside the printed wiring board with the heat sink, the gas (for example, air) of the working atmosphere confined around the conductive pattern is formed through the notch. It is released to the outside through the path to the atmosphere, and is prevented from entering the inside of the conductive pattern. That is, in this case, the notch functions as a gas vent path for the gas in the atmosphere confined around the conductive pattern.

Further, another printed wiring board with a heat sink according to the present invention has a predetermined element fixed to one surface of the heat sink and a conductive pattern disposed opposite to the one surface. A printed wiring board is bonded to the periphery of the element via an adhesive sheet, the element is electrically connected to the printed wiring board, and the element and a part of the printed wiring board adjacent to the element are joined together. In a printed wiring board with a heat sink, which is resin-sealed, a cutout is formed in the adhesive sheet from the vicinity of the conductive pattern to the outer end of the adhesive sheet.

By adopting such a configuration, as described above, the gas (air) in the atmosphere confined around the conductive pattern is released to the outside atmosphere through the notch and does not enter the inside of the conductive pattern. .

Further, the printed wiring board with a heat sink according to the present invention is configured such that the conductive pattern is formed substantially continuously at the same width on the outer periphery of the element.

The printed wiring board with a heat sink according to the present invention is configured such that the conductive pattern is a ground pattern.

Further, the printed wiring board with a heat sink according to the present invention is configured such that the adhesive sheet has an adhesive surface on both sides.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show sectional views of an embodiment of a printed wiring board with a heat sink according to the present invention.
This printed wiring board with a heat sink is a printed wiring board 1,
Predetermined element (chip) 2, radiator plate 3, and adhesive sheet 4
Etc.

The printed wiring board 1 is made of, for example, epoxy resin, and is provided on one surface, for example, the back surface of the printed wiring board 1, as shown in FIGS.
A ground pattern 11 is formed. Further, the printed wiring board 1 has four openings 12 for disposing the elements 2 inside.

Here, the ground pattern 11 is formed by continuously forming patterns of the same width in a rectangular shape, and in a state where the printed wiring board with a heat sink is assembled.
It is located on the outer periphery of the element 2. As an example, the ground pattern 11 has a thickness of 18 μm and a width of 1.5 to 2 mm.
In addition, a conductive pattern (not shown) for signals is formed on the other surface, that is, the surface of the printed wiring board 1.

The element 2 is, for example, an integrated circuit.
The element 2 is connected to a predetermined portion of a conductive pattern formed on the surface of the printed wiring board 1 by wire bonding (connection by a thin conductive wire 5), as described later. On the other hand, the heat radiating plate 3 is made of a material having good thermal conductivity such as an aluminum plate.

Further, the adhesive sheet 4 has an adhesive surface on both sides, and is specifically made by applying an adhesive or an adhesive to the surface of a resin sheet or a paper sheet. The adhesive sheet 4 is used for bonding the heat sink 3 to the printed wiring board 1 as described later. Therefore, the adhesive sheet 4 has substantially the same shape as the printed wiring board 4,
Openings 42 corresponding to the respective openings 12 are formed.

Further, a notch 41 is formed in the adhesive sheet 4, and the notch 41 is formed on the back surface of the printed wiring board 4 in a state where the heat sink 3 is bonded to the printed wiring board 4 via the adhesive sheet 4. Is formed from the vicinity of the ground pattern 41, that is, from the ground pattern 41 and its periphery to the outer end of the adhesive sheet 4.

Next, the procedure for manufacturing the printed wiring board 1 with a heat sink will be described. First, the back surface of the printed wiring board 1 is bonded to the surface of the heat sink 3 via the adhesive sheet 4. Next, a heat conductive adhesive 7 such as an epoxy resin adhesive containing silver powder is applied to the center of the ground pattern 41 on the back surface of the printed wiring board 1, that is, inside the opening 42, on the surface of the heat sink 3. Then, the element 2 is bonded.

Thereafter, the element 2 is electrically connected to a predetermined conductive pattern on the surface of the printed wiring board 1 by bonding using a conductive wire 5 such as a gold wire. Finally, a liquid epoxy resin is applied to the element 2 and a portion of the printed wiring board 1 adjacent to the element 2, and the epoxy resin is heated and cured to seal the element 2 and the bonding portion with the resin sealing material 6. I do.

In the printed wiring board 1 with a heat sink of the embodiment configured as described above, when the back side of the printed wiring board 1 is adhered to the surface of the heat sink 3 via the adhesive sheet 4, the ground pattern 11 In the peripheral portion, air in the working atmosphere is trapped between the adhesive sheet 4, the printed wiring board 1, and the ground pattern 11. Then, the air expands due to heat during the period from the application of the epoxy resin to the heating and curing, and the volume increases.

However, as described above, the printed wiring board 1
Is formed continuously around the periphery of the element 2 so as to surround the periphery of the element 2, the ground pattern 11 prevents the inflated air from entering the ground pattern 11. Is done.

Further, as described above, since the notch 41 extending from the ground pattern 41 on the back surface of the printed wiring board 4 to the outer end of the adjacent adhesive sheet 4 is formed in the adhesive sheet 4, the expanded air Is released to the outside atmosphere through the notch 41 and does not enter the ground pattern 11. As a result, it is possible to prevent the occurrence of voids in the sealing resin when the sealing resin is cured by heating.

In the above embodiment, the case where the configuration in which the ground pattern 11 is continuously formed on the outer periphery of the element 2 and the configuration in which the adhesive sheet 4 having the notch 41 is used has been described. Even when only one of the configurations is provided, a sufficient effect is achieved, and the air that has thermally expanded into the ground pattern 11 is prevented from entering.

That is, as shown in FIG. 4, the notch of the adhesive sheet 4 may be omitted, and the ground pattern 11 may be formed continuously on the outer periphery of the element 2. Alternatively, as shown in FIG. The notch 41 is formed in the adhesive sheet 4 and the ground pattern 11
May be formed in a substantially U-shape.

[0030]

As described above, according to the printed wiring board with the heat radiating plate of the present invention, it is possible to prevent the occurrence of voids in the sealing resin when the sealing resin is cured by heating. It is possible to avoid such a problem that stress is applied to the wire inside the stop portion to cause a connection failure or a conduction failure, or that the sealing strength is reduced due to incomplete sealing.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of a printed wiring board with a heat sink according to the present invention.
FIG. 2 is an exploded perspective view showing the embodiment.

FIG. 2 is an enlarged sectional view of a main part of the printed wiring board with a heat sink shown in FIG.

FIG. 3 is a plan view of a main part of the printed wiring board with a heat sink shown in FIG. 1;

FIG. 4 is a second view of the printed wiring board with a heat sink according to the present invention.
It is a top view which shows embodiment.

FIG. 5 is a third view of the printed wiring board with a heat sink according to the present invention.
It is a top view which shows embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Printed wiring board 2 ... Element 3 ... Heat sink 4 ... Adhesive sheet 5 ... Wire 11 ... Ground pattern (conductive pattern) 12 ... Opening 41 ... Notch 42 ... Opening

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuki Kumagai 5-36-11 Shimbashi, Minato-ku, Tokyo F-term in Iwaki Electronics Co., Ltd. (reference) 5E322 AA11 AB06 FA06 5E336 AA04 BB02 BC34 CC31 CC51 DD22 DD32 DD39 GG03 GG30 5E338 AA16 BB63 BB71 BB75 CC01 CC06 CD17 CD22 EE02 EE11 EE21

Claims (6)

[Claims] 1. A printed wiring board (1) having a predetermined element (2) fixed to one surface of a heat sink (3) and having a conductive pattern (11) arranged opposite to said one surface. ) Is adhered to the periphery of the element via an adhesive sheet (4) to electrically connect the element to the printed wiring board and to combine the element and a part of the printed wiring board adjacent to the element together. A printed wiring board with a heat sink, wherein the conductive pattern is formed continuously on the outer periphery of the element. 2. The adhesive sheet (4) according to claim 1, wherein a notch (41) extending from the vicinity of the conductive pattern (11) to the outer end of the adhesive sheet is formed. Printed wiring board with heat sink. 3. A printed wiring board (1) having a predetermined element (2) fixed to one surface of a heat radiating plate (3) and having a conductive pattern (11) arranged opposite to said one surface. ) Is adhered to the periphery of the element via an adhesive sheet (4) to electrically connect the element to the printed wiring board and to combine the element and a part of the printed wiring board adjacent to the element together. A printed wiring board with a heat sink, wherein a cutout from the vicinity of the conductive pattern to the outer end of the adhesive sheet is formed in the adhesive sheet. Board. 4. The device according to claim 1, wherein said conductive pattern is formed continuously on the periphery of said element with substantially the same width. Printed wiring board with heat sink. 5. The printed wiring board with a radiator plate according to claim 1, wherein the conductive pattern is a ground pattern. 6. The printed wiring board with a heat sink according to claim 1, wherein the adhesive sheet (4) has an adhesive surface on both sides.