JPS5952554B2 - Manufacturing method of printed wiring board - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in a method for manufacturing printed wiring boards.

BACKGROUND ART Conventionally, printed wiring boards in which a circuit pattern made of a conductor layer is formed on the surface of an insulating substrate made of resin have been widely used.

However, this type of printed wiring board has the problem of high thermal resistance and poor heat dissipation, and has been subject to significant restrictions on miniaturization. In other words, since the resin substrate is mainly composed of resin material, it has low thermal conductivity and does not contain resistors, transistors, or I/O devices that generate a large amount of heat.
When an electric element such as C is mounted, heat from this electric element cannot be effectively removed. For this reason, there have been problems such as difficulty in reducing the size of printed wiring boards on which electric elements that generate a large amount of heat are mounted. In addition, the method of forming a conductor layer on a resin substrate using an electroless plating method, that is, the aditetsubu method, requires special chemical treatment when roughening the surface of the resin substrate in order to increase the adhesion with the conductor layer. And so. The present invention has been made in consideration of the above circumstances, and its purpose is to improve the heat dissipation properties and realize miniaturization when manufacturing printed wiring boards, as well as to improve the heat dissipation properties of the printed wiring boards and to realize the miniaturization of the printed wiring boards. It is an object of the present invention to provide a method for manufacturing a printed wiring board that can strengthen the adhesion without requiring chemical treatment.

First, an overview of the present invention will be explained. The present invention is a method in which a ceramic layer is formed by spraying an insulating ceramic material onto the surface of a resin substrate, and then a conductor pattern is formed on the ceramic layer. Therefore, according to the present invention, the conductor layer forming the conductor pattern comes into contact with the ceramic layer having excellent thermal conductivity, and it is possible to significantly improve heat dissipation. Therefore, even when an electric element that generates heat is mounted, the device can be made smaller. Further, since the ceramic layer formed by thermal spraying firmly adheres to the resin substrate and the conductor layer, it is possible to improve the adhesion between the resin substrate and the conductor layer. below,
The details of the invention will be explained by means of illustrated embodiments.

FIGS. 1a to 1e are diagrams showing the manufacturing process of a printed wiring board according to an embodiment of the present invention.

First, as shown in FIG. 1A, a resin substrate 1 such as a glass-epoxy substrate is prepared, and the upper surface (surface) of this substrate 1 is roughened. Then, a ceramic material having excellent insulation and thermal conductivity is thermally sprayed onto the upper surface of the substrate 1 to form a ceramic layer 2 as shown in FIG. 1B. Here, if the thermal spraying conditions are appropriately selected, a part of the thermal sprayed ceramic material can be embedded into the resin substrate 1, as shown in FIG. 2, which is a partially enlarged view of FIG. Strong adhesion between ceramic layer 1 and ceramic layer 2 is ensured. As the ceramic material to be thermally sprayed, alumina, zirconia, magnesia, titania, boron nitride, silicon nitride, aluminum nitride, etc. may be used alone or a composite material containing these as main components can be used. The thickness of the ceramic layer 2 by thermal spraying is 10 [μm] or more.
00 [μm] or less is preferable. This is ceramic layer 2
If the thickness is less than 10 [μm], the effect of dissipating heat and ensuring adhesion when a conductive layer is formed will be insufficient. In addition, the thickness of the ceramic layer 2 is 200 [μm]
] If this is the case, problems such as a decrease in adhesion between the resin substrate 1 and the ceramic layer 2 due to the difference in thermal expansion between the resin substrate 1 and the ceramic layer 2 occur. Next, two methods were used to form a conductive pattern on the thermally sprayed ceramic layer 2.

The first conductor pattern forming method is a method using electroless plating. First, palladium colloid, which will become the nucleus of electroless plating, is deposited on the ceramic layer 2, and then a reverse pattern of the required circuit is formed as shown in FIG. 1C. Print Messuki Resist 3 on the surface. Next, as shown in FIG. 1d, a metal layer (conductor layer) 4 is deposited in a desired pattern in an electroless plating bath.
Thereafter, the resist 3 is removed to produce a printed wiring board as shown in FIG. It goes without saying that the conductor pattern can also be formed by a known method that uses electrolytic plating in combination. The feature of this first conductor pattern forming method is that the thermal sprayed ceramic layer 2 is formed on the resin substrate 1.
It has been found that the ceramic material serves as a good base layer for the electroless plating layer. To explain this mechanism, the ceramic material flying through the high-temperature plasma gas collides with the substrate 1 in a molten state.

This retained heat and momentum cause the ceramic particles to stick to the resin substrate 1. Then, the flying ceramic powder is deposited on the ceramic. In this case, the ceramic layer 2 does not completely fuse with the previous ceramic layer, but instead leaves a space and is deposited one after another in a very complex shape, so the surface of the ceramic layer 2 becomes extremely rough as shown in Figure 2 above. It has a complicated structure. When metal is deposited on this surface by electroless plating, the legs of the plating grow into the intricate pores of the ceramic layer 2, as shown in FIG. 2 and the substrate 1 is firmly secured. In other words, the resin substrate 1 and the conductor layer 3 are firmly attached. On the other hand, the second conductor pattern forming method involves printing and forming a thermal spray resist in a reverse pattern of the desired pattern on the resin substrate 1 having the thermal sprayed ceramic layer 2, and then thermal spraying a conductive metal by selecting thermal spraying conditions. This is a method of selectively forming conductor patterns.

The conductive metal may be copper, aluminum, nickel, silver, gold, etc., but copper or nickel is preferred from the viewpoints of electrical conductivity, solderability, and economy. Moreover, a normal resin resist is sufficient as the thermal spray resist.

Here, the reason why a conductive layer is formed selectively is explained. Since the surface on which the conductive pattern is to be deposited is the surface of the thermally sprayed ceramic layer 2, the surface is roughened as mentioned above, and the thermally sprayed metal film is easily deposited. . On the other hand, since the sprayed resist layer has a smooth surface made of resin, by reducing the spray speed of the metal spray, the sprayed metal powder is deposited only on the ceramic layer, and the sprayed metal powder is deposited on the resist layer. It is easily possible to select conditions that do not allow deposition. In this way, a desired conductor pattern can be formed by both the first and second methods. Next, a step of impregnating the voids of the thermally sprayed ceramic layer 2 with a heat-resistant resin is performed.

This method of impregnating the resin may be performed by performing an impregnation treatment after forming the ceramic layer 2, but in this case, it is necessary to eliminate the surface irregularities of the ceramic layer 2 to ensure strong adhesion between the ceramic layer 2 and the conductor layer 4. Since this cannot be ensured, it is necessary to remove the resin remaining on the surface layer by steam cleaning or the like. Alternatively, after forming the conductor pattern,
A method may also be used in which a heat-resistant resin is impregnated from the surface layer by a vacuum impregnation method or the like, impregnated into the ceramic vine layer 2, hardened, and then ground 5 until the conductor layer 4 is exposed. When impregnated with a resin, it has the effect of preventing a decrease in insulation resistance due to moisture adsorption in the ceramic layer 2 and improving the mechanical brittleness of the sprayed film. The impregnating resin that can be used here is preferably a thermosetting resin with good insulation properties, such as epoxy resin, diallyl phthalate resin, 1,2 polybutazinine resin, polyimide resin, thermosetting acrylic resin, polyester resin, bismaleimide. Resin, silicone resin, etc. can be used.

Thus, according to the method of this embodiment, heat dissipation performance can be greatly improved compared to conventional printed wiring boards, thereby making it possible to miniaturize the circuit.

Moreover, the adhesion between the resin substrate 1 and the conductor layer 3 can be strengthened, and reliability can be improved. moreover,
The manufacturing process also has advantages such as being relatively simple. Furthermore, when a printed wiring board was actually produced by applying the method of the present invention, the following results were obtained.

A glass base epoxy substrate J (MEL-44 manufactured by Toshiba Chemical Corporation) with a thickness of 1.6 [Mm] was 100 [Mm]
The substrate was cut to a size of 100 [Mm], and 80 meshes of alumina powder was sandblasted on the surface of the substrate to roughen the surface.
At this time, the distance between the peaks and valleys of the surface unevenness is 10 to 300 [μ
m]. Next, using a plasma spraying machine (Plasma 7M manufactured by Daiichi Metco Co., Ltd.) using argon nitrogen gas,
Alumina powder having a purity of 98% or more and a particle size distribution of 100 μm was thermally sprayed. In this case, the nozzle of the thermal spraying machine is scanned so as to uniformly coat the entire surface of the substrate, and an average of 50 [μ
The amount of alumina sprayed was obtained. Next, palladium colloid was deposited on this substrate by an electroless plating process (P-T-H Process 2 manufactured by Shippray Japan Co., Ltd.) in order to deposit palladium colloid as a core of electroless plating. Furthermore, a screen paste prepared from epoxy resin with a reverse pattern of the required conductor pattern was printed on this and cured by heating. Next, an electroless copper plating bath (Metex 904 manufactured by MacDamide Inc.) was used.
8), a plating thickness of 20 [μm] was obtained. Next, 500 [Ω] prepared from carbon black and phenol resin.
/? ] The printing resistance ink was printed to have a size of 5 [Mm] x 5 [Mm]. Next, 160 [℃]
1 [H] After firing, this was designated as Sample 1. As a comparison sample, a copper-clad glass-epoxy substrate made of the same base material was patterned into the same pattern, and a resistance pattern was prepared using the same resistance ink, which was prepared as Sample 11. Next, a solder resist was printed on both samples 1 and 11, serving as both a protective coat for the resistor and a solder resist, and was baked at 150 [° C.] for 30 [minutes]. Each resistance value is 5
It was possible to adjust within 00 [Ω] ±20 [%].

By applying a power of 1/4 [W] to these resistors, 70 [
As a result of applying a current of 1000 [H] at a cycle of 90 [minutes] 0n30 [minutes] 0ff, data as shown in FIG. 4 was obtained. That is, in Sample 1, the rate of change in resistance was extremely small, as shown by curve A in FIG. 4, and was about -6% even after 1000H. On the other hand, in sample 11, curve B
As shown in Figure 2, the rate of change in resistance was extremely large, about -30% after 100H. In addition, by varying the type of resistor ink and the area of the resistor, the allowable power amount (maximum power amount for which the change in resistance value after 1000 [H] in the above loading test is within ±10 [%]) As a result, we obtained the relationship between allowable power amount and resistor area as shown in the following table. As is clear from this relationship, it has been found that by applying the present invention, the size of the substrate can be significantly reduced even when mounting a heating element.

Regarding the formation of the conductor, instead of the plating method of this example, a screen paste made of the epoxy resin is printed, and a copper conductor is formed by plasma spraying copper powder using nitrogen gas and hydrogen gas as a thermal spray resist. A sample prepared in the same manner as in this example showed the same results as in this example.

Note that the present invention is not limited to the embodiments described above.

For example, the method for forming the conductive pattern is not limited to the electroless plating method or the thermal spraying method, and various methods can be applied. Further, the step of impregnating the ceramic layer with resin is not necessarily necessary, and may be omitted as appropriate depending on the specifications. Further, the sprayed ceramic material forming the ceramic layer and the metal material forming the conductor layer may be determined as appropriate depending on the specifications. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

1A to 1E are diagrams showing the manufacturing process of a printed wiring board according to an embodiment of the present invention, and FIGS. 2 to 4 are diagrams for explaining the operation of the above embodiment. FIG. 1B is a partially enlarged view of FIG. 1B, FIG. 3 is a partially enlarged view of FIG. 1E, and FIG. 4 is a characteristic diagram showing experimental data. ]... Resin substrate, 2... Ceramic layer, 3... Luggist, 4... Conductor layer.

Claims (1)

[Claims] 1. A print characterized in that a ceramic layer is formed by spraying an insulating ceramic material on the surface of a resin substrate, and then a desired conductive pattern is formed on the ceramic layer. Method of manufacturing wiring boards. 2. The method for manufacturing a printed wiring board according to claim 1, wherein the means for forming the conductor pattern is to deposit a conductor layer in a desired pattern on the ceramic layer by electroless plating. . 3. The means for forming the conductor pattern is to print a thermal spray resist on the ceramic layer in a pattern opposite to the desired conductor pattern, and then thermally spray a conductive metal material to form a conductor layer in the desired pattern. A method for manufacturing a printed wiring board according to claim 1, characterized in that: 4. The method of manufacturing a printed wiring board according to claim 1, wherein the ceramic layer is formed only on a desired portion of the surface of the resin substrate. 5. The method of manufacturing a printed wiring board according to claim 1, wherein the ceramic layer is impregnated with a heat-resistant resin.