JPS61194893A - Formation of conductive circuit on substrate - Google Patents

Abstract

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

Description

TECHNICAL FIELD The present invention relates to a method of forming conductive paths on the surface of a substrate according to a predetermined shape.

[Prior Art and its Problems] Substrates having conductive paths on the surface and inside thereof have been known for a long time. A good example is a printed circuit board. According to printed circuit board technology, conductive paths are formed on the surface of the substrate by an additional process that adds the conductive pattern itself or by a removal process that removes unnecessary parts of the conductive material and leaves the desired conductive pattern. There is.

A prior art example of combining additive and subtractive processing techniques is disclosed in US Pat. No. 3,438,127 (Lehtonen patent). In this patent, a mold with extended protrusions is used to form a grooved substrate, and a conductive material is provided in the grooves of the substrate. In the above-mentioned patent, electroless plating is used to accumulate conductive material in the grooves.
(lating) and electroplating are recommended.

The technique described in the above-mentioned patent has the drawback of requiring a number of processing steps, which is not economically advantageous and wastes a lot of production material.

For example, when the entire surface of a substrate is plated, conductive materials other than the grooves must be removed by polishing or machining.Furthermore, the substrate may be coated with wax or plating to control the areas to be plated or coated. In cases where careful processing is required with materials that cannot be used, not only is there an additional step of coating the substrate with wax or other suitable material, but the wax must be removed afterwards, and the removed wax is usually Furthermore, the known techniques described above do not lend themselves well to automation in forming conductive paths on the surface of a substrate.

[Object of the Invention] The present invention is to provide a method that solves the above-mentioned conventional problems.

The present invention is a method for forming a path made of a predetermined material in a groove of a predetermined width provided on the surface of a substrate, the method comprising: (a) preparing a substrate having a groove of a predetermined width on the surface; depositing a layer of reverse electrolyzable material approximately 173 times the width of the groove on the entire exposed surface of the substrate, including the exposed walls, substantially uniformly and in a direction substantially perpendicular to the exposed surface; filling with a reverse electrolyzable material and covering the top of the groove and the exposed surface of the substrate with the reverse electrolyzable material; (c) removing the layer from the surface of the substrate substantially uniformly and exposing the layer by a reverse electrolyzing method; It is characterized in that the layer is removed in a direction perpendicular to the surface so that the layer remains approximately only in the groove.

[Summary of the Invention] According to the present invention, first, a substrate having grooves that specify the shape of a conductive path is prepared, and then the method described in U.S. Pat.
The substrate is then processed according to the prior art disclosed in US Pat. No. 2,796,509 to enable a conductive material to be provided on the surface of the substrate. The conductive material is then deposited substantially uniformly on the exposed surface of the substrate by an electroplating method. do. Note that as long as the conductive material can be accumulated almost uniformly on the exposed surface of the substrate, other methods can be used without being limited to electroplating.Next, the substrate is placed in an electroplating bath, and the exposed surface of the substrate is Accumulate the desired substance. This accumulation of the desired material is continued until the thickness of the desired material layer reaches approximately one-third of the width of the groove. Accumulation of the desired material in the grooves occurs at approximately three times the rate at which the material accumulates in the plane of the substrate. This is because the trench has exposed walls on three sides, so the trench is filled at a faster rate than the flat surface of the substrate, until the surface of the substrate is covered with conductive material and becomes flat with almost no irregularities. Then, the conductive material layer is gradually and substantially uniformly removed. In the case of electroplating, the polarity of the substrate is reversed to that in which the desired material is deposited, and the conductive material deposited on the substrate is removed from the substrate except in the trenches. Other methods of removing accumulated substances.

This is a method of removing metal or conductive material from the surface of a substrate using an etching solution. In this way, the conductive material is left only inside the groove, and the conductive material on other surfaces of the substrate is removed.

It is clear that according to the method described above, circuits with different patterns can be processed in succession. That is, the substrate is placed in an electroplating bath for a predetermined time (time to form a layer of a desired thickness, determined experimentally) and then taken out;
Place it in a reverse electrolytic tank and remove the conductive material leaving it only in the grooves0
The substrate is then removed from the reverse electrolytic bath and cleaned to complete the desired conductive pattern.

The substrate is preferably made of green or fired ceramic (green is a granular mixture mixed with a binder and molded into a desired shape), but substrates made of other materials, such as plastic, can also be used. The substrate in the green state can be used, for example, in U.S. Pat. No. 2,939,199, U.S. Pat. No. 4,197.118, U.S. Pat.
A green substrate disclosed in No. 756 or the like can be used. The green substrate provided with conductive paths can also be doped with other substances inside the mold, for example by the method disclosed in US Pat. No. 4,374,457.

The conductive material that accumulates on the substrate may be a single metal or an alloy as long as it can be fixed to the substrate. An example of such an alloy is an alloy of 58% iron and 48% nickel. It is. The reason for this is that the coefficient of thermal expansion of this alloy is approximately equal to the coefficient of thermal expansion of # aluminum (suitable as a substrate material). In order to accumulate the above-mentioned alloys on a substrate, it is well known that the substrate is treated with iron ions and nickel ions.
It may be placed in an electrolytic solution with an ion ratio of 58:42.

Furthermore, this specification discloses a cross-section of a groove that improves the shape of the groove and mechanically strengthens the fixation of a conductive material provided in the groove.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a simplified cross-sectional view of a portion of a substrate similar to that shown in the above-mentioned US Pat. No. 4,379,457. The substrate shown here is preferably made of aluminum oxide (ceramic), but is not limited to this, and may be made of other ceramics such as beryllium oxide, or may be made of materials such as plastics well known to those skilled in the art. It is also possible to do this. It should be noted that any of these materials can be used for the substrate according to the invention, which is designated with reference numeral 1 and has a two-dimensional surface 7 on top. This surface 7 has grooves 3 for receiving conductive material and wells 5 for receiving semiconductor chips and the like. The shape of the conductive pattern to be formed is determined by the shape of the groove 3 on the substrate surface. The present invention relates to a method for forming a conductive path inside the groove 3.

FIG. 2 is a simplified cross-sectional view of one of the grooves 3 in FIG. 1, enlarged. FIG. 2 also shows the conductive material 9 being formed on the surface of the substrate l. The step of coating the conductive material 9 is to provide the conductive material 9 substantially uniformly over the entire exposed portion of the substrate l, and any method may be used as long as the conductive material 9 can be provided substantially uniformly. Uniform coating of can be achieved by electroplating or other well known techniques.

As can be seen from FIG. 2, the growth (accumulation) of conductive material in the grooves 3 is approximately three times as large as in the planar surface 7. The reason for this is as follows. That is, the growth of the conductive material is uniform over the entire exposed surface, since there are three exposed surfaces inside the groove 3. Therefore, when the thickness of the conductive layer 9 reaches approximately 1/3 of the half width of the groove 3, the entire groove 3 is filled with the conductive material, and the surface of the substrate 1 having the conductive material 9 becomes as shown in FIG. As shown, it is clear that it approaches a plane.

On the other hand, regarding the recess 5, the width of the recess 5 is much larger than the thickness of the conductive layer 9 to be accumulated.

As shown in FIG. 4, the corners are slightly rounded, and the conductive material is uniformly accumulated on the entire wall of the recess 5.

FIG. 5 shows how the conductive material 9 has accumulated on the substrate 1. The conductive material 9 is then removed at a uniform rate from the entire surface of the substrate 1 by conventional methods, e.g. by electroplating. When a conductive substance is accumulated, the direction of the current is reversed to uniformly remove the conductive substance from the surface of the substrate (reverse electrolysis method).As mentioned above, the surface of the conductive layer 9 is a flat surface with almost no irregularities. (see Fig. 5), it is possible to remove all the conductive material from the flat part 7 of the substrate 1, except for the vicinity of the corners of the groove 3 and the recess 5 (the conductive material in this part is indicated by 11). Yes (see Figure 6).

The accumulation and removal of the conductive material described above is accomplished as follows. First, a substrate as shown in FIG. 1 (i.e., the substrate shown in the aforementioned U.S. Pat. No. 4,374,457 patent)
For example, the above-mentioned U.S. Pat. No. 3,438
, 127, or other known techniques, the substrate surface is treated to accumulate a conductive material (in the above description, an electroplatable material) on the surface of the substrate.The substrate is then electroplated. The substrate is placed in a bath, and a conductive material is accumulated on the surface of the substrate to a thickness of about 173 to about 172 times the width of the groove 3. At this point, the direction of the current in the electroplating bath is reversed and the conductive material begins to be removed, so that there is no conductive material on the planar portion 9 of the substrate l and there is conductive material inside the groove 3. Then, the substrate is removed from the electroplating bath and subjected to subsequent steps.

Apart from the above-mentioned case, the conductive material is deposited on the substrate to the desired thickness by electroplating, the substrate is removed from the electroplating bath, and this substrate is placed in another electroplating bath in the reverse manner as in the case of conductive layer accumulation. By any of the methods described here and the method mentioned at the beginning, a current may be passed in the direction.
It is clear that continuous processing is possible.

Yet another method is to use conductive air drying inks often used in thick film silk screen circuit printing. In this method, first, the dirt is completely removed from the substrate so that the appropriately diluted ink completely adheres to the substrate and grooves (i.e., the ink has a minimum contact angle with the substrate). , by spraying the substrate with ink or dipping the substrate in a reservoir of ink so that a thin layer of ink covers the substrate and the ink fills the grooves. Again, use the wetting phenomenon to fill the groove with ink, and
To obtain the same result as shown in Figure 6, the substrate is then cleaned of excess ink by soaking or spraying with solvent or by solvent vapor cleaning, as shown in Figure 6. Make it.

It is clear that if the trench is quite deep, it will be difficult for the current to reach the deepest part of the trench, and the electroplating solution will be dilute in the deepest part of the trench. For this reason, it is desirable to agitate the interior of the electroplating bath in order to minimize the aforementioned depletion and ensure that maximum current reaches the entire surface of the substrate.

Although a preferred embodiment of providing a conductive material on the external surface of the substrate has been described, it is clear that any surface of the substrate accessible to the plating current can be coated with a conductive material. therefore,
It is clear that grooves or holes within the substrate leading to the external surface of the substrate can also be provided with conductive material, provided that these grooves and holes can also be penetrated by the plating solution and reached by the plating current. In this way, electrically conductive paths can also be formed in internal regions of the substrate in one step.

The conductive pattern can be fixed to the substrate mechanically in addition to being fixed to the substrate chemically as described above.

This mechanical method can further reduce the possibility that the conductive pattern will peel off from the substrate. Mechanical fixation of the conductive material is carried out by changing the groove 3 of FIG. 1 in its cross section (perpendicular to the axis of the groove). Figure 7 shows the top surface 3.
5 shows the groove 33 formed in a step shape. FIG. 8 shows an enlarged cross section of the step 37. As shown in FIG. extends upward to the right. On the other hand, the step 39 similarly has a parallelogram cross section, with both sides thereof extending upwardly to the left.

The continuous conductor formed in the groove 33 is fixed in the groove 33,
It is clear that due to its geometry it does not easily disengage from the groove. Furthermore, if such an effect is obtained,
It is clear that cross-sectional shapes other than parallelograms may be used.

[Brief explanation of drawings]

FIG. 1 is a simplified cross-sectional view of a part of a substrate on which a conductive material is provided;
FIG. 2 is a partially enlarged sectional view of the groove (FIG. 1) in the process of providing a conductive material, and FIG. 3 is a partial enlarged cross-sectional view of the groove (FIG. Figure 4 is an enlarged cross-sectional view of a recess (Figure 1) provided with a conductive material, and Figure 5 is a cross-sectional view of the substrate (Figure 1) showing the completed accumulation of conductive material. Figure 6 is a cross-sectional view of the substrate showing how the conductive material has been removed leaving some grooves and recesses, Figure 7 is a plan view of the substrate with a conductive pattern formed on the substrate, and Figure 8 is Figure 7. FIG. 9 is a cross-sectional view taken from line 9--9 in FIG. 7. Substrate 3.33: Groove 5: Recess 7 Surface of two substrates 9: Accumulated layer

Claims (1)

[Claims] (1) A method for forming a path made of a predetermined material in a groove of a predetermined width provided on the surface of a substrate, comprising: (a) preparing a substrate having a groove of a predetermined width on the surface; (b) on the entire exposed surface of the substrate, including the exposed walls of the groove;
depositing a layer of reverse electrolyzable material approximately uniformly and generally perpendicular to the exposed surface to a thickness of about 1/3 the width of the trench, filling the trench with the reverse electrolyzable material and filling the trench with the reverse electrolyzable material; (c) removing the layer from the surface of the substrate by a reverse electrolysis method;
A predetermined material is removed substantially uniformly and in a direction substantially perpendicular to the exposed surface of the layer so that the layer remains only substantially in the groove, and the predetermined material is removed in a groove of a predetermined width provided on the surface of the substrate. How to form a path consisting of. 2. The method of claim 1, wherein step (2) includes immersing the substrate in an electroplating solution and electroplating the layer onto the substrate. (3) The layer is made of a conductive material.
The method described in section. (4) The layer is made of a conductive material as claimed in claim 2.
The method described in section. (5) The method according to claim 1, wherein said step (c) includes flowing a current in the opposite direction through said electroplating solution. (6) The method according to claim 3, wherein said step (c) includes flowing a current in the opposite direction through said electroplating solution. (7) The method according to claim 4, wherein said step (c) includes flowing a current in the opposite direction through said electroplating solution. 8. The method of claim 7, wherein said substrate is comprised of an aluminum oxide ceramic and said layer is an alloy of approximately 58% iron and 42% nickel. 9. The method of claim 1, wherein the substrate is a green ceramic, and following step (c), the binder is removed from the substrate and sintered. 10. The method of claim 1, wherein the substrate is an aluminum oxide ceramic and the layer is an alloy of about 58% iron and 42% nickel. 11. The method of claim 2, wherein said substrate is comprised of an aluminum oxide ceramic and said layer is an alloy of approximately 58% iron and 42% nickel. 12. The method of claim 3, wherein said substrate is comprised of an aluminum oxide ceramic and said layer is an alloy of approximately 58% iron and 42% nickel. 13. The method of claim 4, wherein said substrate is comprised of an aluminum oxide ceramic and said layer is an alloy of approximately 58% iron and 42% nickel. 14. The method of claim 5, wherein said substrate is comprised of an aluminum oxide ceramic and said layer is an alloy of approximately 58% iron and 42% nickel. (15) The method of claim 2, wherein the substrate is a green ceramic, and following step (c), the binder is removed from the substrate and sintered. (18) The method of claim 3, wherein the substrate is a green ceramic, and following step (c), the binder is removed from the substrate and sintered. (17) The method of claim 4, wherein the substrate is a green ceramic, and following step (c), the binder is removed from the substrate and sintered. (18) The method of claim 5, wherein the substrate is a green ceramic, and following step (c), the binder is removed from the substrate and sintered. 19. The method of claim 7, wherein the substrate is a green ceramic, and following step (c), the binder is removed from the substrate and sintered. (20) The method of claim 8, wherein the substrate is a green ceramic, and following step (c), the binder is removed from the substrate and sintered. (21) The method of claim 14, wherein the substrate is a green ceramic, and following step (c), the binder is removed from the substrate and sintered.