JPS6235693A - Circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a circuit board with a novel configuration.

[Conventional technology]

Currently, circuit boards such as printed circuit boards are mainly manufactured using the etching method or the additive method, but the line width of the conductive pattern is usually about 20 μm using the etching method and 100 to 150 μm using the additive method. However, in recent years, with the miniaturization of packaging technology and miniaturization of devices, there has been a demand for smaller circuit boards, and for discrete ICs, etc., the line width is required to be thinner than 100 μm. By the way, in order to meet this demand, various attempts have been made in the past, especially using the above-mentioned additive method, but in this additive method, ceramics are often used as one of the substrate materials.In this case, for example, , Ceramic circuit boards are made by printing conductive wires on a thin sheet-like ceramic plate and firing it.

That is, by printing pulverized conductor powder together with a binder,
Metal powder is sintered to reduce electrical resistance. There is also a method of creating the conductive part by plating. That is, for example, a conductive pattern is created by appropriately activating a ceramic plate to deposit plating. in this case,
There is a method in which plating is deposited on the entire surface of the substrate and then etched leaving the conductive portions, and a method in which plating is deposited only on the conductive portions.

[Problem that the invention seeks to solve]

By the way, the line width of the conductive portion, that is, the circuit portion of the printed circuit board manufactured by the above-mentioned former manufacturing method is determined by the printing accuracy, so the limit value of the line width that can be obtained is about 100 μm.
Furthermore, since the printed circuit boards manufactured by either of the latter methods described above go through a printing process, only line widths of approximately the same degree can be obtained, and in the latter case, the adhesion to the substrate is weak, which poses a practical problem.

SUMMARY OF THE INVENTION In view of these problems, an object of the present invention is to provide a circuit board in which conductive portions having an extremely narrow line width of 100 μm or less can be obtained uniformly and with high precision.

[Means and effects for solving the problem] In the circuit board according to the present invention, the conductive pattern is formed as a groove on the surface of the electrically insulating sheet-like substrate material, and the groove is filled with a conductive material. ing. A ceramic sheet or a plastic sheet is used as the substrate material, and a metal such as copper or nickel is used as the conductive material.

〔Example〕

Hereinafter, the present invention will be specifically explained using an example in which ceramic is used as the substrate material. In Figure 1, 1
2 is a ceramic substrate in which a groove 1a of a predetermined depth corresponding to a circuit pattern is formed; 2 is a conductive material such as copper or nickel filled in the groove 1a; It is necessary that it has a trapezoidal shape that spreads toward the surface of the upper substrate 1. That is, the opposing side surfaces of the groove 1a may be flat or part of a spherical or ellipsoidal surface, but the apex angle θ of the side surface is 90° or more, the angle between the substrate surface and the groove side surface, that is, the cutting point. It is necessary that the angle θ2 is 90° or less.

Next, a method for manufacturing the ceramic substrate 1 will be explained.

Normally, it is difficult to cut ceramics, and it is difficult to form the grooves 1a by cutting. Therefore, the groove processing is performed at the raw material stage, that is, the so-called green sheet stage.
This is done by pressing a stamper, which has a convex part corresponding to the circuit pattern and a concave part in other parts, onto a green sheet placed on a plastic film carrier.

Stampers include roll-shaped stampers and flat-plate stampers, and stampers made of various materials such as metal, plastic, and rubber can be used. These stampers are created by applying the production method of ordinary letterpress printing plates, but if the pattern requires high density and high precision, a letterpress plate obtained by high-precision ultraviolet exposure baking can be electroformed. It is created by transferring it onto a high hardness metal such as nickel. Such a stamper can also be obtained using a laser-sensitive resist, but when using a laser beam, not only can the trapezoidal cross section of the groove be freely selected, but also the program data for creating the circuit network can be directly used to drive the laser. Above 6 explained how to manufacture circuit boards using green sheets, which have the advantage of being able to be used as data.
This circuit board can also be manufactured using a mixture of ceramic raw materials and a binder. In this case, the mixed material is poured into a mold incorporating the stamper, or injection molded or compression molded using the mold, and then fired.

Next, a method of filling the groove la with the conductive material 2 will be described.

Metals such as copper and nickel are generally used as the conductive material 2, and these metals can be used by activating the surface of the ceramic substrate 1 obtained as described above using, for example, tin chloride or palladium chloride. Thereafter, by electroless plating, it is deposited over the entire surface or partially at necessary locations, thereby filling the grooves la. At this time, if it is necessary to make the metal layer sufficiently thick, electrolytic plating may be used in combination.In addition, vapor deposition, sputtering, etc. may be used to fill the ala with the conductive material 2. A vapor phase method may be used, or a method of directly filling metal paste, amalgam, etc. may be used, but when using a vapor phase method, it is necessary to combine it with an electrolytic plating method to obtain a sufficient thickness of the metal layer. It is also possible to secure it. Also, when using metal paste or amalgam, etc., hardening or ? Even if processes such as fI melting are added, line width accuracy is not affected.

The thus obtained ceramic plate with conductive material is completed by removing the conductive material adhering to the surface portions other than the portions corresponding to the grooves. The conductive material is removed by appropriate means such as mechanical polishing (grinding 1) and depolishing (etching 51).

In the above embodiments, the case where ceramic is used as the substrate material has been explained, but the present invention is not limited to this. Any suitable material selected from inorganic materials that can be formed by compression molding may be used.

According to experiments, it was possible to obtain a conductive pattern with a line width of 30 μm and a thickness of 30 μm with extremely high reproducibility.

〔Effect of the invention〕

According to the present invention, it is possible to provide a circuit board in which the line width and line spacing of conductive parts can be made extremely small and uniform, and therefore, it is possible to realize a wiring network with hole density wiring and hole precision. I can do it. Further, according to the present invention, since the conductive portion is recessed into the inside of the substrate, the bonding force between the substrate and the conductive portion is strong and the R-shaped portion will not peel off from the substrate under any usage conditions. Not only can it withstand long-term use, but also the board surface and the surface of the conductive part are on the same plane, so there is an advantage that the mounted components can be mounted reliably and accurately. Furthermore, according to the present invention, it is possible to finish with a relatively small number of steps without going through processes that have elements that make the dimensions unstable, such as printing, baking, firing, melting, and etching, so miniaturization is easy. It has the advantage that it can be manufactured at low cost.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a circuit board according to the present invention, and FIG. 2 is a partially enlarged view of FIG. 1. 1...Substrate material, 1a0. ... Groove, 2... Conductive material.

Claims (3)

[Claims] (1) A circuit board formed by forming a groove corresponding to a circuit pattern in an electrically insulating substrate material and filling the groove with a conductive material. (2) The circuit board according to claim (1), wherein ceramic is used as the substrate material and metal is used as the conductive material. (3) The circuit board according to claim (1), wherein plastic is used as the substrate material and metal is used as the conductive material.