JP2001068798A - Printed wiring board with heat-radiating plate and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a joint between a metal heat-radiating plate and a printed wiring board in the heat resistance and insulation reliability. SOLUTION: An insulating plate 3 is interposed between a metal heat radiating plate 1 and a printed wiring board 2, the heat radiating plate 1 and the insulating board 3 are bonded together with an adhesive sheet 4 which is high in resin fluidity, and the insulating board 3 and the wiring board 2 are bonded together with an adhesive sheet 5 of high resin fluidity. The leads 8 of an electronic part 7 which generates heat are connected to a wiring pattern 9 formed on the opposite surface of the wiring board 2 with solder 11. By this structure, a stable joint can be obtained through the characteristics of the adhesive sheets 4 and 5, and resin does not flow out of the adhesive sheet 5, even if a hot press process is carried out under usual wiring board laminating conditions. Furthermore, the printed wiring board of this constitution can be ensured of high dielectric strength by the insulating board 3.

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 structure and a manufacturing method of a printed wiring board with a heat sink.

[0002]

2. Description of the Related Art Since a large-capacity heat-generating component is mounted on a printed wiring board used for a power supply device or the like, a printed wiring board provided with a metal radiating plate is used to improve heat dissipation. Can be As described in JP-A-62-7191, an insulating layer is provided directly on the surface of a metal plate for heat radiation, and the structure of the printed wiring board with a heat sink is matched with the through hole of the printed wiring board. After opening the lead wire holes, it is joined to the wiring board via an adhesive sheet.
Further, as described in JP-A-8-264910, a metal radiator plate is provided on the insulating substrate side of the printed wiring board, while a through hole is provided in the printed wiring board at a place where the heat-generating component is mounted, thereby generating heat. There is known a structure in which a component directly contacts a metal heat sink.

[0003] From these known examples, a printed wiring board with a heat radiating plate as shown in FIG. 4 can be easily constructed. As shown in the drawing, a metal heat radiating plate 1 is provided on a surface of a wiring board 2 on which a heat generating component is mounted by an adhesive sheet 4, and lead wires 8 of the heat generating component 7 mounted on the heat radiating plate 1 are passed through through holes 6 and through holes 10. Through to the printed wiring with solder 10.

[0004]

In the above-described structure of the conventional printed wiring board with a heat radiating plate, the heat generating component can be brought into contact with the heat radiating plate, so that the heat radiating effect is large.
As described above, a surface mount component having a small amount of heat generation can be mounted on the back surface of the wiring board, so that the mounting density can be improved. However, when the metal radiator plate and the printed wiring board are joined by heating and pressurizing using a normal adhesive sheet (prepreg), the resin component of the adhesive sheet is heated and pressurized through the through hole through which the lead of the heat-generating component passes. There is a problem that it sometimes flows out and adheres to a through hole of a printed wiring board, hinders lead insertion, and causes poor soldering. Further, Japanese Patent Application Laid-Open No. 62-7191,719
In the case of No. 2, the insulating layer 2 made of a prepreg or the like directly provided on the surface of the heat-dissipating metal plate 1 also flows out during heating and pressurization, and there is a concern that a sufficient withstand voltage cannot be obtained.

If an adhesive sheet (low-flow prepreg) with reduced resin fluidity is used to improve the resin outflow, a sufficient adhesive strength cannot be obtained between different kinds of materials of the metal radiator plate and the printed wiring board. Therefore, there has been a problem that delamination or the like occurs during soldering of the electronic component.

Also, as an insulating layer replacing the prepreg,
Solder resists and powder molds are conceivable, but the former is liable to cause poor quality such as pinholes, and the latter has a problem that the processing steps are complicated and a flat insulating layer cannot be obtained. For this reason, sufficient insulation withstand voltage cannot be secured between the wiring pattern provided on the joint surface with the metal radiator plate and the metal radiator plate, and it is applied to a multilayer printed wiring board requiring a high withstand voltage. Can not.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems by preventing the adhesive or the like from flowing out of the metal heat radiating plate, thereby enabling a strong connection between the heat radiating plate and the wiring board. An object of the present invention is to provide a plate structure and a manufacturing method. It is another object of the present invention to provide a printed wiring board structure and a manufacturing method by which a stable and high withstand voltage insulating layer can be easily obtained.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a printed wiring board to which a metal heat radiating plate for dissipating heat of an electronic component is joined, wherein an insulating layer is provided on one surface of the heat radiating plate. Wherein the insulating layer and the printed wiring board are joined via an adhesive sheet having low resin fluidity.

Alternatively, an insulating plate serving as an insulating layer is interposed between the heat radiating plate and the printed wiring board, and the heat radiating plate and the insulating plate are joined to each other via an adhesive sheet having a high resin fluidity. The printed wiring boards are joined to each other via an adhesive sheet having low resin flowability.

In addition, a through hole for inserting a lead of a heat-generating electronic component mounted in contact with the heat radiating plate is coaxial with the through hole of the printed wiring board (substantially the same center line).
And the through hole has a larger diameter than that of the through hole.

Further, the heat radiating plate is provided on a wiring pattern surface of the printed wiring board. Thereby, a multilayer printed wiring board with a heat sink can be configured.

A printed wiring board with a heat sink according to the present invention comprises the steps (a) to (d).

(A) a step of providing an insulating layer on one surface of the heat sink, (b) a step of temporarily bonding a first adhesive sheet having low resin fluidity to the insulating layer, and (c) the first bonding. Providing a through-hole corresponding to the through-hole of the printed wiring board in the heat-dissipating plate after the sheet is temporarily bonded; (d) connecting the heat-dissipating plate provided with the through-hole to the printed wiring via the first adhesive sheet; A step of joining the board by heating and pressing.

Alternatively, it is preferable that an insulating plate is used as the insulating layer, and the insulating plate is bonded to the heat radiating plate by applying heat and pressure in the step (a) using a second adhesive sheet having a large resin fluidity. Features.

The insulating plate is made of a glass-epoxy material or a glass-polyimide material, and the first adhesive sheet is made of a glass-epoxy or glass-based resin having a resin flowability of 10% or less.
For the second adhesive sheet such as a low flow prepreg of polyimide, a prepreg of glass-epoxy or glass-polyimide having a resin flowability of 30% or more is used.

According to the present invention described above, the heat dissipating plate made of metal and the insulating plate (layer) are joined by an adhesive sheet having a high resin fluidity capable of favorably joining different kinds of materials. Since it is the same kind of material as the insulating plate on the heat sink side, it is joined with an adhesive sheet having low resin fluidity. As a result, it is possible to prevent the resin from adhering to through holes and the like due to the flow of the adhesive sheet resin generated at the time of heating and pressing. In addition, since sufficient insulation withstand voltage can be secured by the insulating plate provided on the metal heat sink side, there is no problem even if a wiring pattern is provided on the surface of the printed wiring board when the heat sink is joined,
Application to a multilayer substrate is also possible.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 and 2 of the present invention will be described below in detail. FIG. 1 shows manufacturing processes (A) to (D) of a printed wiring board according to Embodiment 1 of the present invention. In (a), for example, an insulating resin layer 12 having a thickness of about 0.05 to 0.1 mm made of, for example, an epoxy material or a polyimide material is provided on a metal heat sink 1 made of an aluminum plate or an aluminum alloy plate. As a method of providing this resin layer, there is a method of applying a powdery resin and then heating and curing, or a method of printing a liquid resin and heating and curing the resin.

In (b), the adhesive sheet 5 with resin flowability is temporarily bonded to the insulating resin layer 12 side. As the adhesive sheet 5, for example, a glass-epoxy or glass-polyimide low-flow prepreg having a resin flowability of 10% or less is used.
Glue under condition ² .

In (c), the through holes 6 are drilled or pressed in the heat sink 1 with the adhesive sheet 5 adhered thereto. This through hole 6 is a through hole 1 of the printed wiring board 2.
0, and the diameter is slightly larger than the through hole 10.

In (d), the radiator plate 1 processed in the steps (a) to (c) is attached to the printed wiring board 2 by the adhesive sheet 5.
To each other by hot pressing. Since the adhesive sheet 5 having low resin flow is used as the heating and pressurizing condition at this time, it can be carried out under the ordinary laminating condition for a printed wiring board.

In the printed wiring board with a metal heat radiating plate according to this embodiment, an insulating resin layer made of a material similar to that of the printed wiring board is provided on the metal heat radiating plate side in advance, so that the heat radiating plate and the printed wiring board can be joined. Even if an adhesive sheet with low resin fluidity is used, both are well adapted to each other and a certain degree of bonding strength can be secured. Therefore, it is possible to avoid the problem that the resin of the adhesive sheet flows out and adheres to the through holes when joining the heat radiating plate and the wiring board by heating and pressing, so that unnecessary labor in the manufacturing process can be omitted and the product quality can be improved.

In the first embodiment described above, the metal radiator plate side
In order to secure the bonding strength by using an adhesive sheet having a low resin flowability, an insulating resin layer which can be called a dummy is provided.
Since this insulating resin layer has a thickness of about 0.05 to 0.1 mm, it is possible to secure a certain withstand voltage together with the bonding strength. However, it is not always sufficient when a high withstand voltage is required as in a multilayer printed wiring board. Next, a second embodiment in which this point is improved will be described.

FIG. 2 shows a process (a ') to (d') for manufacturing a printed wiring board according to Embodiment 2 of the present invention.
In (a '), a metal heat radiating plate 1 made of an aluminum plate or an aluminum alloy plate and an insulating plate 3 having a thickness of about 0.1 mm are heated and pressed by a hot press via an adhesive sheet 4 having good resin fluidity. Perform bonding. The insulating plate 3 is made of a glass-epoxy material or a glass-polyimide material, and the adhesive sheet 4 is made of a glass-epoxy prepreg or a glass-polyimide prepreg having a resin flowability of about 30 to 60%. 130 ° C as a stage, 5 kg / c
Hot pressing is performed at 180 ° C. and 30 kg / cm ² as the second stage in m ² .

In (b '), an adhesive sheet 5 used for bonding to a printed wiring board and having reduced resin fluidity is temporarily bonded to the insulating plate 3 side. The material of the adhesive sheet 5 and the temporary bonding method are the same as those in the first embodiment.

The subsequent steps are the same as those in the first embodiment. In (c), a through hole 6 for inserting a lead of an electronic component is provided in the metal heat sink 1 to which the adhesive sheet 5 is temporarily bonded.
In (d), the metal heat radiating plate 1 and the printed wiring board 2 processed in the steps (a ′), (b ′) and (c) are hot-pressed via the adhesive sheet 5 in which resin fluidity is suppressed. Bonding by heating and pressing. The heating and pressurizing conditions at this time are the same as those in the first embodiment, and can be carried out under the ordinary printed wiring board laminating conditions.

In the printed wiring board with a metal heat radiating plate according to the second embodiment, a good resin fluidity is obtained in which the different materials of the metal radiating plate and the insulating plate are well adapted to both and have a stable bonding strength. It is joined using a suitable adhesive sheet.
Incidentally, in the test by the inventors, no problem such as delamination occurred at all even in the soldering heat test at 260 ° C. for 300 seconds.

Further, when joining to a printed wiring board, since the same kind of material is used for the insulating plate and the wiring board, a stable joining strength can be obtained even when joining with an adhesive sheet having suppressed resin fluidity. . Further, in the hot press under the ordinary printed wiring board laminating conditions, there was no outflow of the resin of the adhesive sheet at all, and there was no problem such as adhesion to a through hole provided in the printed wiring board.

FIG. 3 shows a mounting structure of a printed wiring board with a heat sink according to the second embodiment. An electronic component 7 that generates heat on the heat sink 1 and a surface-mounted electronic component 7 ′ that generates a small amount of heat are provided on the surface of the wiring board 2 where the heat sink does not exist. Note that elements equivalent to those in FIG. 2 are denoted by the same reference numerals.

The heat radiating plate 1 made of metal having excellent thermal conductivity and the insulating plate 3 are joined by an adhesive sheet 4 having high resin fluidity, and the insulating plate 3 and the printed wiring board 2 are joined by an adhesive sheet 5 having low resin flowing property. Are joined. The leads 8 of the heat-generating electronic component 7 are inserted through the through holes 6 of the heat sink 1 and the corresponding through holes 10 of the wiring board 2, and are connected to the wiring pattern 9 on the opposite surface of the wiring board 2 by solder 11. . The diameter of the through hole 6 is slightly larger (about 1 mm) than the land portion of the through hole 10 to prevent the leads 8 of the electronic component 7 from contacting the metal heat sink 1, The hole diameter is set such that a predetermined creepage distance with the plate 1 can be secured.

According to this, since the package of the electronic component 7 that generates heat is mounted in close contact with the metal radiator plate 1, it is possible to obtain a good heat radiation effect. Further, since an insulating plate exists between the metal heat radiating plate and the printed wiring board, a sufficient withstand voltage can be ensured even if a wiring pattern is provided on the heat radiating plate joint surface of the printed wiring board. In the test, insulation breakdown did not occur even when DC 1500 V was applied between the metal heat sink and the wiring pattern, and this embodiment can be applied to a multilayer printed wiring board requiring a high withstand voltage.

[0031]

According to the present invention, since the adhesive sheet having low resin fluidity is used for bonding the heat sink made of metal and the printed wiring board via the insulating layer, the resin flows out during hot pressing. Can prevent the resin from adhering to the through-holes, making it easy to manufacture and improving the product quality.

Further, according to the present invention, an insulating plate is interposed between a metal heat radiating plate and a wiring board, and an adhesive sheet having high resin flowability between the heat radiating plate and the insulating plate, and a resin flowing between the insulating plate and the wiring board. Since it is joined using a highly adhesive sheet,
A stable bonding strength can be obtained by preventing resin outflow under ordinary wiring board lamination conditions, and a high dielectric strength can be ensured due to the interposition of the insulating plate.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a manufacturing process of a printed wiring board with a metal heat sink according to Embodiment 1 of the present invention.

FIG. 2 is an explanatory view showing a manufacturing process of a printed wiring board with a metal heat sink according to Embodiment 2 of the present invention.

FIG. 3 is a sectional view showing a mounting structure of a printed wiring board with a heat sink according to a second embodiment.

FIG. 4 is a cross-sectional view showing a mounting structure of a conventional printed wiring board with a heat sink.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heat radiating plate, 2 ... Printed wiring board, 3 ... Insulating plate, 4 ... Adhesive sheet, 5 ... Adhesive sheet, 6 ... Through hole, 7, 7 ... Electronic component, 8 ... Lead, 9 ... Wiring pattern, 10 ... Through Holes, 11: solder, 12: insulating resin layer.

Claims (7)

[Claims] 1. A printed wiring board to which a metal heat sink for dissipating heat of an electronic component is joined, an insulating layer is provided on one surface of the heat sink, and the insulating layer and the printed wiring board are formed of resin fluidity. A printed wiring board with a heat radiating plate, which is joined through an adhesive sheet having a small size. 2. A printed wiring board to which a metal heat radiating plate for dissipating heat generated by an electronic component is joined, wherein an insulating plate serving as an insulating layer is interposed between the heat radiating plate and the printed wiring board. The heat insulating plate is characterized in that the insulating plates are joined via an adhesive sheet having a high resin fluidity, and the insulating plate and the printed wiring board are joined via an adhesive sheet having a low resin fluidity. Printed wiring board. 3. The heat radiating plate according to claim 1, wherein a through hole through which a lead of a heat-generating electronic component mounted in contact with the heat radiating plate is inserted is coaxially formed with the through hole of the printed wiring board. A printed wiring board provided with a heat sink, wherein the diameter of the through hole is larger than that of the through hole. 4. The printed wiring board according to claim 2, wherein the heat sink is provided on a wiring pattern surface of the printed wiring board. 5. A method for manufacturing a printed wiring board for joining a metal heat radiating plate for dissipating heat generated by an electronic component, comprising the following steps (a) to (d): Manufacturing method of printed wiring board with board. (A) providing an insulating layer on one surface of the heat sink;
A step of temporarily bonding a first adhesive sheet having low resin fluidity to the insulating layer; (c) a through-hole corresponding to a through-hole of the printed wiring board in the heat sink after temporarily bonding the first adhesive sheet; (D) bonding the heat sink provided with the through holes to the printed wiring board by heating and pressing via the first adhesive sheet. 6. The method according to claim 5, wherein an insulating plate is used as the insulating layer, and the step (a) uses a second adhesive sheet having high resin fluidity in the step (a).
A method for producing a printed wiring board with a heat radiating plate, which is a step of heating and pressing to join the heat radiating plate. 7. The low-flow prepreg according to claim 6, wherein the insulating plate is a glass-epoxy material or a glass-polyimide material, and the first adhesive sheet is a glass-epoxy or glass-polyimide resin having a resin flowability of 10% or less. A method for manufacturing a printed wiring board with a heat sink, wherein a glass-epoxy or glass-polyimide prepreg having a resin flowability of 30% or more is used for the second adhesive sheet.