JPH0358492A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To enable a printed wiring board to be improved in heat dissipating property and mounting density, simplified in structure, and manufactured at a low cost by a method wherein a thin part is partially provided to a conductive plate through a mechanical method, an inorganic insulating layer is formed on a metal base, the conductive plate is bonded to the metal base with an organic bonding agent, and the disused part of the conductive plate is removed to form a circuit pattern. CONSTITUTION:A conductive plate 33 which forms a circuit pattern is previously separated into three parts, a heat sink part 43, a conductive path part 73, and a part 53 which is removed by etching through a mechanical processing, where three parts are different from each other in thickness. That is, the heat sink part 43 is formed thick, the etched part 53 is thin or removed to be left irreducibly minimal, and the conductive path part 73 is formed thick or thin corresponding to a current which flows through it. Moreover, an inorganic insulating layer 31 is formed on a metal base 21, then the processed conductive plate 33 is pasted thereon, and the part 53 thin and disused is removed by etching. By this setup, a printed wiring board can be improved in mounting density and heat dissipating property, simplified in structure, and manufactured at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a printed wiring board with excellent heat dissipation effects.

[Subject technology] In recent years, the amount of power used has increased, as typified by fields such as power supply circuits, drive circuits for various motors, and power amplifier circuits.
In order to meet the needs for high-density packaging of circuits and miniaturization of equipment, a printed circuit board with good heat dissipation is required, and the manufacturing method for providing such a printed circuit board is shown in Figure 5 (a). ) to (d) and the manufacturing method shown in cross-sectional view in FIG. 6 are known.

That is, FIG. 5(a) is a cross-sectional view of a metal-based A-stripe laminate. Gold for printed wiring boards that require heat dissipation!
14 Use an aluminum plate or a copper plate as the base material,
The insulating material 12 uses an epoxy resin that has both the ability to bond the copper 13 and the gold X base material 1 1 and electrically insulate it, but glass epoxy prepreg is used to further strengthen the insulation. Sometimes I do. Copperwork 3 has a thickness of 30 to 10
It is a copper foil of 0 μm, and the thickness of the insulating material 12 is 40 to 150 μm.
It is μm. As shown in FIG. 5(b), an etching resist 4 is applied to this copper-clad 1A layer board to form a circuit pattern 1. 'Form. Next, as shown in FIG. 5(c), copper 1
By etching and removing the exposed portion of the copper plate 3 and peeling off the etching resist 4, a circuit pattern of the copper plate 3 is formed. Next, as shown in FIG. 5(d), a heat sink 15 made of copper, with a thickness of <0.5 to 3 nm and a size of several m1 to several meters is soldered onto a circuit nozzle. This will be glued. A high heat generating element such as a power transistor, a power MOS-FET, or a thyristor is incorporated on the heat sink 5.

Next, in Figure 6, copper foil is used as the copper work 3 (instead of 1, a thick II1 copper plate that can also be used as a heat sink is used).
A printed wiring board is formed.

The manufacturing method is the same as that shown in FIGS. 5(a) to 5(C), and the drawing corresponds to FIG. 5(c) after the etching of the copperwork 3 has been completed and the etching resist has also been removed.

[Problem H to be Solved by the Invention] The first problem to be solved by the present invention in printed wiring boards in which such high heat generation elements are incorporated is that the circuit pattern is highly accurate and the printed wiring board is capable of high-density mounting. To provide a simple and inexpensive manufacturing method for a wiring board. In other words,? In the manufacturing method shown in Figs. 15(a) to (d), the heat sinks 5 must be bonded one by one onto the circuit pattern by soldering, and the positional accuracy of the bonding due to alignment, rotation, etc. It is not only a difficult process, but also a time-consuming process.

On the other hand, if a large number of heat sinks are to be formed at once, the manufacturing method shown in FIG. 6 will be used, and since the copper work 3 is thick, etching will take a very long time.

In addition, because the copper is thick, side etching of the copper progresses during etching, resulting in a cross section of the copperwork 3 that is narrow at the top and wide at the bottom, resulting in poor pattern accuracy and difficulty in forming fine lines. become. Therefore, it is not possible to form a printed wiring board that can be mounted at high density.

It is an object of the present invention to solve the above-mentioned problems and to further improve heat dissipation.

[Means for solving the problem: A circuit with good heat dissipation? In order to provide a simple and inexpensive manufacturing method for a printed wiring board that has highly accurate turns and can be mounted at an iE"lB degree, the heat sink portion, The copper thickness of each part is divided into the electrical circuit section and the section that will be removed by etching.In other words, the heat sink section is removed, the etched section is thinned or removed so that only a minimum remains, and the electrical circuit section is designed to absorb the current flowing through it. It is processed to make it thicker or thinner depending on the amount.

Further, the metal base material is subjected to an inorganic insulation treatment, and then the processed conductive plates are bonded together, and the thin and unnecessary portions of the conductive plates are etched away to form a printed wiring board. Organic TI made of organic adhesive by inorganic insulation treatment of gold IA base material! A: Reduce the thickness of the edge layer to improve heat conduction and improve heat dissipation.

Furthermore, in order to obtain a high-density mounting printed wiring board, a multilayer structure is adopted in which an insulating layer is formed on a conductive plate and a conductive layer is further formed on the insulating layer.

[Operations] A step of mechanically forming at least one of a partially thinned part and a missing part on a conductive plate as described in the claims 1 and 1, and the surface of a metal base material. A printed wiring board comprising the steps of: applying an inorganic insulation treatment to the conductive plate; adhering the conductive plate to the metal base material with an organic adhesive; and removing unnecessary parts of the conductive plate to form a circuit pattern. By using this manufacturing method, the heat sink portion and the electric circuit portion can be formed using the conductive plate alone before being bonded to the metal base material. In addition, the accuracy of the circuit pattern is improved,
It becomes easier to automate the process, including the mounting of high heat generation elements in the post-process.

Furthermore, the presence of the inorganic insulating layer allows the thickness of the organic insulating layer made of an organic adhesive to be reduced, increasing the thermal conductivity of the entire insulating layer and improving heat dissipation. There are roughly the following differences between resin and ceramic (inorganic insulating layer) in terms of heat conduction, f, and f.

Resin 0. 1 ~ 0. 2 Kcal/m
-hr・”c Ceramic Approximately 10 Kcal
/m-hr・"c Therefore, the thermal conductivity is much improved and the heat dissipation property is improved compared to the case where the insulating layer is formed only with resin.

As described in claim 2, by including the steps of forming an insulating layer on a part of the conductive plate and forming a conductive layer on the insulating layer, the multilayer structure can be stacked. It is possible to make a printed wiring board with a high structure, and it is possible to increase the packaging density.

As stated in claim 3, gold! ! 4 The base material is aluminum, and the manufacturing method includes a process of alumite treatment on at least one side of the metal base material, making it easy and accurate to control the thickness of the inorganic insulating layer using aluminum as the base material. A film can be easily formed,
Further, due to the alumite layer having good thermal conductivity, it is possible to provide a printed wiring board with excellent heat dissipation.

[Examples] Examples of the present invention will be described below. FIGS. 1(a) to 1(f) showing the first embodiment are sectional views of a printed wiring board in the order of steps.

Conductive plate 3 made of copper material with a thickness of 2 mm as shown in Fig. 1(a)
3 is press-formed as shown in drawing (b) to form unevenness on one side. Here, the convex portion 43 is a portion corresponding to a heat sink. The concave portion 53 to be compressed and deformed should be as thin as possible, preferably 50 μm. The recessed portion 53 consists of a portion that will be etched away in the end and a portion that will become an electric path 73 with a relatively small amount of current. The portion of the recess 53 that is removed by etching is a portion for connecting the convex portion 43 or the electric circuit 73, and it is sufficient to leave a minimum portion for this purpose.

FIG. 2 shows this as a drawing, and an unnecessary part is punched out to form a cutout part 63. In the first drawing, an example is shown in which the convex part 43 and the concave part 53 are separated.
Depending on the case, portions with an intermediate thickness or a wider variety of thicknesses may be provided. FIG. 3 shows such an example, and in a circuit through which a medium current flows, an electric path 73 is formed in this intermediate thickness portion. Note that post-process 61
In order to enhance the adhesive effect of the bonding shown in FIG. 11(d), fine irregularities were formed on the bonding surface of the conductive plate 33. Possible forming methods include a method of forming using a mold during pressing, a method of forming by electroplating, or a method of forming chemically.

Figure 1 (c) is gold! It is a sectional view in which three inorganic insulating layers are formed on the surface of two A base materials. In this example, aluminum with a plate thickness of 1.5 mm is used as the metal base material 21, and an inorganic insulating layer 3 of alumite (thickness 20 μm) is formed by M polar oxidation method in a sulfuric acid solution.
1, and sealing the holes with acrylic electrodeposition paint to ensure electrical insulation. Note that the three inorganic insulating layers can also be formed by a thermal spraying method, a sputtering method, or the like.

Next, as shown in FIG. 1(d), the metal base material 21 and the -J electric plate 33 are bonded together. For bonding, use an organic adhesive with good thermal conductivity. The organic adhesive material is an organic adhesive such as F-2 (manufactured by Rokuto Sangyo), and is applied to a coating thickness of about 50 μm on a gold aX material (aluminum) 2 piece using a roll coater. After coating, the solvent is evaporated by treatment at 160° C. for 10 minutes.

The thickness of the organic insulating shoulder 22 made of this organic adhesive after the solvent has evaporated is approximately 20 μm, and a conductive plate 33 having irregularities is placed thereon and bonded by press. Pressing conditions are temperature 180
The time is 30 minutes at a temperature of 100 kg/caf and a pressure of 100 kg/caf.

Next, as shown in FIG. 1(e), an etching resist 24 in the form of a circuit pattern is formed on the conductive plate 33. The pattern formation method is screen printing or a method using a photosensitive resist. When using a photosensitive resist, irradiation with LIV light using an exposure mask or direct drawing method is also possible. When using screen printing As an example of the etching resist, X-77 (manufactured by Ohsumi Ink) is used, and after printing, dry explosion is carried out at 80° C. for 10 minutes.

Next, as shown in FIG. 1(f), the conductive plate 3 other than the electric path 73
Etch the thin portions of 3 to separate the connected patterns. The etching solution used when the conductive plate 33 is made of copper is as shown below.

C u C 1!・2H! 0 2 0
0 g / 137%HC1 150g
/1 Solution temperature: 45° C. After etching, remove the etching resist flfl. The resist stripping solution is as shown below.

NaOH 100g/1 liquid fL
40°C Next, a second embodiment of the present invention aimed at high-density mounting on printed wiring boards will be described. Figure 4(a). As shown in (b), multilayer wiring is formed in which the second conductive layer consists of a circuit with a relatively small amount of current.

First, as shown in FIG. 4(a), the embodiment shown in FIG. 1(a)
to (f), a thickness of approximately 60 μm is placed on the convex portion (heat sink portion) 43 of the printed wiring board created in FIGS. 2 and 3.
The insulating layer 32 (after drying and curing) is partially formed by screen printing. An adhesive such as F-2 (manufactured by Ohbe Sangyo) can be used as the material for this insulating layer 32.

Next, as shown in FIG. 4(b), a conductive layer 83 having a thickness of about 35 μm is formed on the rounded layer 32 by screen printing a conductive paste (copper paste), drying and baking. This conductive layer 83 can be formed by electroless plating on the insulating layer 32 or by electroplating after electroless plating, or by transferring a conductive layer that has been formed by electroplating onto a stainless steel plate or the like. It is also possible to climb up and form.

[Effects of the Invention] A step of mechanically forming at least one of a partially thinned portion and a deleted portion on a conductive plate as described in claim 1; The method for producing a printed wiring board includes the step of bonding to a metal base material with an organic adhesive and the step of removing unnecessary parts of the conductive plate to form a circuit pattern, thereby making the conductive board before being bonded to the metal base material. Since the thick part (heat sink part) and the thin part (11-way part) can be formed independently, it becomes an easy-to-manufacture method suitable for mass production that can be processed in batches, and the cost can therefore be reduced.

In addition, the circuit pattern accuracy is high and high-density wiring is possible, making it easier to automate the process including mounting high heat generation elements in the subsequent process, stabilizing the process and speeding up the work to reduce the number of parts mounted on printed wiring boards. It is possible to improve reliability.

As described in claim 1, by inorganically insulating the surface of the gold R base material, the thickness of the organic insulating layer made of the organic adhesive of the printed wiring board can be reduced, and the thickness of the entire insulating layer can be reduced. Thermal conductivity increases and heat dissipation improves. This means that a small heat sink is sufficient (
Therefore, it can be used as a high-density mounting printed wiring board.

As stated in claim 2, a part of the conductive plate is
By using a manufacturing method that includes a step of forming one layer and a step of forming a conductive layer on the insulating layer, it is possible to create a printed wiring board with a stacked multilayer structure and increase the packaging density. It becomes possible.

As stated in claim 3, gold+! ! The base material is aluminum, and the gold! ! ! Since at least one side of the base material is anodized, aluminum is used as the base material, and the thickness can be easily and accurately controlled as an inorganic insulating layer.An oxide film with high insulation properties can be easily formed, and it also has excellent heat dissipation. Printed wiring boards can be manufactured at low cost.

[Brief explanation of drawings]

Figure 1 (a), (b), (c), (d), (e), (f
) is a cross-sectional view showing the process of manufacturing a printed wiring board of the present invention, FIGS. 2 and 3 are cross-sectional views showing different embodiments of the conductive plate of the present invention after press molding, and FIG. 4(a) , (b) is a sectional view showing different manufacturing method steps of the present invention, FIG. 5(a),
(b), (C), and (d) are cross-sectional views showing steps of a conventional printed wiring board manufacturing method, and FIG. 6 is a cross-sectional view of another conventional printed wiring board. 11, 21...Metal base material Work 2...Insulating material 13.
・・M 15・=−Heat sink insulating layer 31・
...Inorganic insulating layer 33...Conductive plate 83...Conductive layer 22...Organic 32...Insulating layer

Claims (3)

[Claims] (1) A step of mechanically forming at least one of a partially thinned portion and a missing portion on the conductive plate, a step of inorganic insulation treatment on the surface of the metal base material, and a step of forming the conductive plate on the conductive plate. A method for manufacturing a printed wiring board, comprising the steps of: bonding a plate to the metal base material with an organic adhesive; and removing unnecessary portions of the conductive plate to form a circuit pattern. (2) The printed wiring board according to claim 1, which includes the steps of forming an insulating layer on a part of the conductive plate and forming a conductive layer on the insulating layer. Manufacturing method. (3) The printed wiring according to claim 1 and claim 2, wherein the metal base material is aluminum, and includes a step of alumite treatment on at least one side of the metal base material. The manufacturing method of the board.