JPS5932917B2 - Multilayer wiring board manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a multilayer wiring board, and more particularly to a method of economically manufacturing a wide variety of multilayer wiring boards with different wiring connections.

Conventionally, when multilayer wiring boards used for mounting multichip LSIs and the like are used in large computers, etc., multilayer wiring boards with over 100 different types of wiring connections are required.
Since it is a typical high-mix, low-volume product, there were problems in terms of economy.

In order to clarify this problem, an example of a conventional method for manufacturing a multilayer wiring board will be explained with reference to FIGS. 1 to 5.
Figure 1 is a wiring connection diagram taken as a model. Here, terminals Y2, Y1', Y4' and X1 are connected, terminals Y3, Y2', X5 and X3' are connected, and terminals Y5, X2, X2' and X5' are connected.
We will explain the case where this wiring connection is realized using, for example, the most common thick-film multilayer wiring board. First, each layer pattern is designed.
The wiring is divided into a first conductor layer and a second conductor layer, respectively.
The conductor layer is patterned with a predetermined wiring width and wiring pitch. The insulating layer that insulates the first conductor layer and the second conductor layer is
A pattern is designed in which holes for through holes are formed at locations where connections are to be made between the wiring in the first conductor layer and the second conductor layer. Furthermore, in order to make the through-hole connection more reliable, a pattern (hereinafter referred to as a through-hole connection pattern) is designed in which the through-hole hole in the insulating layer is filled with a conductor. Once the pattern for each layer is designed, a photomask for each layer pattern is manufactured, and then a screen for printing each layer is made for each layer using these photomasks. The above is the preparatory work before manufacturing. Then the actual manufacturing work begins.

Gold paste is printed on the substrate using a screen on which the pattern of the first conductor layer has been made, and after drying, it is fired at a high temperature to form the first conductor layer as shown in FIG. Here, 1 is a substrate, and 2 is a first conductor layer. Next, a paste of crystallized glass is printed on the first conductor layer using a screen on which the pattern of the insulating layer has been made, and after drying, it is fired at a high temperature to form the insulating layer as shown in Figure 3. do.

Note that the insulating layer is formed in two layers to reduce the occurrence of pinholes. That is, the step of forming the insulating layer is repeated twice. Here, 3 indicates the insulating layer, and 4 indicates the hole drilled for through-hole connection. Next, the insulating layer 3 is formed using a screen on which a through-hole connection pattern is made.
A gold paste is printed on top, dried, and then fired at a high temperature to fill the through-hole hole 4 with a gold conductor 5, as shown in FIG.

Finally, gold paste is printed using a screen on which the pattern of the second conductor layer has been made, dried, and then fired at a high temperature to form the second conductor layer 6 as shown in FIG. With the above steps, a thick-film multilayer wiring board is completed, but it is obvious that the wiring connections in FIG. 5A are exactly the same as the wiring connections in FIG. The method for manufacturing a thick-film multilayer wiring board formed by the method has the following problems. The first problem concerns the manufacturing cost of the multilayer wiring board.

As explained above, for each type with different wiring connections, each pattern of the first conductor layer, insulating layer, through-hole connection, and second conductor layer is designed, a photomask for each layer pattern, and a screen made of each layer pattern is prepared. In the case of a wide variety of products, these expenses will be considerable, and if only a small quantity is produced, the proportion of the design cost, mold cost, and tooling cost in the manufacturing cost of the multilayer wiring board is very large. In terms of man-hours, since high-mix, low-volume production is involved, work efficiency is lower in any manufacturing process compared to small-mix, mass production. If we consider such printing work, it becomes clear how inefficient work efficiency is in high-mix, low-volume production. We perform most of the preparatory work such as setting the screen to the screen, aligning the screen and substrate, trial printing and adjusting the printing conditions to find the optimal printing conditions, and post-work such as collecting the paste on the screen and cleaning the screen. This process is time-consuming, and the process of printing on the substrate itself can be completed in an extremely short time. These preparatory work and post-work are necessary each time the screen is replaced, that is, each time each product type and each layer pattern is printed, and if only a small amount of printing is to be performed, the work efficiency is extremely reduced. Regarding material costs, expensive paste is wasted when measuring the viscosity of the paste for each type of product and each layer pattern printed, when it adheres to screens, etc. and cannot be recovered, and during trial printing to find the optimal printing conditions. If the number of printed sheets is small, the wasted amount will be tens of times the amount actually printed on the board and used. As mentioned above, regarding manufacturing costs,
It is clear that design costs, mold costs, jig costs, material costs, and processing costs are all going up in high-mix, low-volume production, leading to an astonishing increase in costs.The second problem is the number of days required for manufacturing. There is.

When it comes to large-scale circuits like multi-chip LSIs, it is unreasonable to expect perfection at the design stage.
Several cycles of prototyping, evaluation, and design changes are required.Therefore, there is an especially strong demand to shorten the time required for manufacturing multilayer wiring boards as much as possible.Moreover, the manufacturing period can be shortened even at the mass production stage. This is a major advantage and is necessary.In contrast, in the conventional method, each layer pattern is sequentially formed on the substrate after designing each layer pattern, manufacturing a photomask, and making a screen, which requires a considerable amount of work. It is impossible to make a wide variety of products in a short time because it takes several days, and as mentioned in the first problem, the work efficiency decreases.The third problem is the second problem.
Related to the above problem, it is often necessary to change wiring connections after a multilayer wiring board is completed or after an IC chip or the like is mounted. In that case, it would be a big economic loss to rebuild from scratch, and there is often not enough time to do so. Therefore, in that case, you would have to change the wiring connections for the completed product. However, it is difficult to deal with this problem using conventional methods.For example, where new connections need to be made, thin conducting wires are soldered,
Alternatively, there is no other way than to connect by thermocompression bonding, but it requires very detailed work and is time-consuming, so it is virtually impossible to change multiple locations.Additionally, unnecessary wiring connections must be cut. Since the lower wiring is covered with an insulating layer and is not exposed, it is subject to severe restrictions. The problem in Figure 4 concerns quality.We want to manufacture products with stable quality with little variation within the same product type or between product types, but this is quite difficult with conventional methods.

This is mainly due to printing work. In printing work, the working conditions change every time the screen is replaced, so even if the optimal printing conditions are set, it is not sufficient, and differences in printing quality such as printing film thickness, printing dimensions, printing defects, etc. occur between types. This affects the electrical characteristics and, in some cases, causes variations in quality that may even affect reliability. In addition, the quality of printing becomes stable only after a certain number of sheets are printed continuously, but in the case of small-lot production, printing ends before reaching that stable area, so the quality of the same product that is produced continuously can be unstable. It can be said that there is considerable variation. Above, we have discussed the problems with conventional methods using the thick-film method for manufacturing multilayer wiring boards as an example, but there is no difference in the manufacturing of other multilayer wiring boards in which each layer is sequentially made with individual patterns. However, the problem was more or less similar to that described above.The purpose of the present invention is to provide a method for manufacturing multilayer wiring boards of various types with different wiring connections economically, reliably, and with high yield. In particular, the method for manufacturing a multilayer wiring board according to the present invention includes the steps of forming a layer of wiring conductors in a certain pattern on a board, and exposing a plurality of predetermined portions of the wiring conductors over substantially the entire conductor width. It is characterized by comprising the steps of covering the wiring conductor with an insulating layer having at least an outlet, and cutting the wiring conductor exposed at the exposed hole at the exposed hole selected according to the required pattern. Alternatively, the method for manufacturing a multilayer wiring board according to the present invention includes the steps of forming a first layer of wiring conductors on a substrate, and exposing a plurality of predetermined portions of the first layer of wiring conductors over substantially the entire conductor width. a step of forming an insulating layer having an exposed opening and a predetermined interlayer connection port; and a step of forming a wiring conductor of the second layer by connecting a predetermined portion with the wiring conductor of the first layer through the l gap; The method is characterized in that it includes a step of removing a predetermined portion of the first layer wiring exposed in the exposure hole.

In the present invention, the wiring conductor pattern of the first layer or the second layer is formed of a standard pattern consisting of repeating a certain pattern, respectively, and a predetermined wiring pattern is formed by arbitrarily cutting each circuit pattern. Alternatively, the present invention can provide a wide variety of multilayer wiring boards having arbitrary wiring connections including at least two conductor layers. In manufacturing, the first conductor layer pattern, insulating layer pattern, second conductor layer pattern, and if necessary through-hole connection patterns are standardized and the second conductor layer pattern is made into the same standard multilayer wiring board regardless of the product type. After forming up to the first conductor layer, the first conductor layer, the second conductor layer, and the first conductor layer and second conductor layer are formed, depending on the wiring connection of each product.
The present invention aims to obtain a wide variety of multilayer wiring boards having arbitrary wiring connections by selectively cutting or removing predetermined portions between the conductor layers of the first conductor layer pattern. For example, the second conductor layer pattern is arranged in the X direction, for example in the Y direction.
After making a multilayer wiring board with a structure in which wiring is arranged in a lattice pattern at a constant pitch in the direction and all the intersections are connected through holes, the first conductor layer, the second conductor layer, and the through holes in between are selectively connected. Any wiring connection can be obtained by cutting to A wiring board with wiring is to be realized.0 First, a standardized pattern for each layer of a multilayer wiring board is designed0.
Here, running up and down in FIG.
2-X2' is arranged in the first conductor layer, and a conductor layer running in the left and right lateral directions, for example in the Y1-Y1'' direction, is arranged in the second wiring layer. , 1st
The standardized pattern of the layers runs uniformly in the vertical direction, that is, in the vertical direction in the figures explained below, between the terminals X1-X1'', X2-X2'', ...X5-X5 in Figure 1.
On the other hand, the standardized pattern of the second layer also runs uniformly in the horizontal direction, between the terminals Y1-Y1', Y2-Y2 in Fig. 1.
5. Make five patterns such as connecting Y5-Y5'' to each other.Next, make a photomask based on the standardized pattern for each layer, and make a screen for each layer pattern.0This In addition to the wiring connection shown in FIG. 1, the work may be done only once, regardless of the number of types of wiring boards required, including cases where changes are required, for example.

Next, the ceramic substrate 1 is printed using a screen on which a standardized first conductor layer pattern according to the present invention is printed.
Gold paste is printed on it to a thickness of about 10 μm, dried and fired at a high temperature to form the first conductor layer 2 as shown in FIG.

Subsequently, as shown in FIG. 7, five through-hole connection holes 4 are formed for each wiring pattern 2 on the first-layer wiring pattern 2 at the portions that intersect with the second-layer wiring pattern, and the through-hole connection holes are formed on the first-layer wiring pattern 2. and the same number of wiring patterns 2 in parallel.
is selectively coated with crystallized glass paste to a thickness of approximately 30 μm twice so as to have an exposed opening 4″ that exposes almost the entire width of the conductor, and then fired to form the insulating layer 3. 0 Next, as shown in Fig. 8, all the through-hole connection holes 4
A conductor layer is filled with gold paste or the like using a screen method or the like and fired to prevent disconnection of the interlayer connection due to breakage at the end and improve reliability. The five second-layer wiring patterns 6 running in the second layer are formed by applying gold paste to a thickness of about 10 μm using a screen method and firing them. Conductive connections are made through through-hole connections 4 at all intersections. Here, a standard multilayer wiring board is obtained in which the first-layer wiring pattern 2 running in the vertical direction and the second-layer wiring pattern 6 running in the left-right direction are all connected at their intersections in a matrix. As can be seen, the standard multilayer wiring board of order 0 can be called a standard multilayer wiring board as shown in Fig. 9 because it is formed in exactly the same way using a standardized pattern regardless of the product type. In the wiring board, the first layer wiring pattern 2 is placed in the exposed opening 4'',
The second layer wiring pattern 6 exposed on the surface can be removed at any desired portion, or if only interlayer connection is not required, the through-hole connection conductor 5 can be selectively removed by etching or the like. For example, the wiring board shown in Fig. 1 can be obtained, and in order to obtain a multilayer wiring board with 0 wiring connections, an example of which will be explained in detail below, a photomask shown in Fig. 10 is designed and manufactured. 0 This photomask is used for chemical etching of conductors using a negative type photoresist, and the dark areas include a portion 7 where the first conductor layer is removed, a portion 8 where the second conductor layer is removed, and a portion 8 where the first conductor layer is removed. It consists of a conductor layer and a part 9 for removing the through-hole connection between the second conductor layer, and by combining these parts, any wiring connection can be obtained by chemical etching, and the standard shown in FIG. When a negative photoresist is applied to the entire surface of the multilayer wiring board, exposed using the photomask shown in FIG. 10, and then developed, the photoresist in the areas corresponding to 7, 8, and 9 in FIG. 10 is removed. The gold conductor in that area is exposed.A positive photoresist may be used here.In this case, the transparent and dark areas of the photomask shown in Figure 10 are reversed.Next, the wiring board after development is etched with gold. The exposed part of the gold is etched away by immersing it in a liquid such as an aqueous solution of iodine and potassium iodide for a suitable period of time. After that, the photoresist is peeled off to obtain the multilayer wiring board shown in Figure 11. Here, 10 , 11, 12 indicate the gold-etched parts.0 Wiring connections in Figure 11 are external terminals X1-X5, Yl-Y5, Xl'-X5', Y
It goes without saying that the wiring connections shown in FIG. 1 are satisfied with respect to Y1'' to Y5'.

In addition to etching removal, a trimming method using a laser or the like may be used.Next, a second embodiment of the present invention will be explained with reference to FIGS. 12 and 13.In this embodiment, the above-mentioned first The shape of the second layer wiring pattern in the embodiment is changed as shown in FIG. 12. In other words, in the first embodiment, the second layer wiring pattern 6 was formed directly on the through hole connection hole 4 However, in this embodiment, the second layer wiring pattern 6'' running in the horizontal direction is formed so as to run on a line apart from the through-hole connection hole 4, and is connected to the through-hole connection hole 4 by a protruding branch-like pattern. and when the interlayer connection made by the through-hole connection hole 4 is unnecessary, the through-hole connection conductor 5
This is achieved by removing the branch-like portions of the second-layer wiring pattern 6 instead of removing the conductor pattern 6, and providing a cutout inside the second-layer conductor pattern 6 as in the first embodiment. This is a highly reliable method that eliminates the need for a standard multilayer wiring board configured in this manner. The gold conductor No. 6 was selectively irradiated with a laser beam using a laser processing machine to cut it, and the wiring connection shown in FIG. 1 was realized as shown in FIG. 13.

The points indicated by 13, 14, and 15 in the figure are examples of the parts where the gold conductor is cut by the laser beam. As explained above, according to the present invention, the following effects are obvious. The first effect of the invention is that when manufacturing multiple types of multilayer wiring boards with different wiring connections, they can be manufactured in exactly the same manner except for the process of sorting the types, so that the conventional high-mix, low-volume production can be improved by eliminating the process of sorting the types. This means that we have been able to shift to the highly desirable production system of mass production of one type, and it is possible to significantly reduce the manufacturing cost of multilayer wiring boards. All that is required is design and photomask production screen printing.
Design costs, mold costs, and jig and tool costs can be significantly reduced compared to the conventional four-layer system.Material costs and processing costs can also be reduced considerably by mass production. In printing operations, the ability to print in large quantities with one screen set-up reduces the amount of time required for preparatory work and post-work, and also reduces the percentage of paste wasted. Extremely significant reduction in material and processing costs is achieved.According to the above, according to the present invention, the work of sorting the types is added in the manufacturing process, but overall it is possible to achieve a significant reduction in the manufacturing cost of multilayer wiring boards. 〇Second aspect of the present invention
The effect of this is that mass production improves work efficiency and makes it possible to manufacture a wide variety of products in a short period of time.
It is also possible to stock-produce the standard multilayer wiring board in advance, and in that case, the multilayer wiring board with the desired wiring connections can be produced by hand in an extremely short period of time, which is highly effective. A third effect of the present invention is that it is easy to change the wiring connections of the multilayer wiring board even after it is completed.

This means that by connecting the parts cut or removed during product classification with solder or conductive adhesive, the original standard multilayer wiring board can be restored, and any wiring connections can be made from there. As can be easily understood from the above, even if an 0C chip or the like is installed, unnecessary wiring connections can be selectively cut at points 13, 14, and 15 in Fig. 13 using a laser beam. Also, the necessary wiring connections can be made by selectively connecting points 13, 14, and 15 using, for example, solder or conductive adhesive.0 Wiring connections can be changed without using any conductive wires. The fourth effect of the present invention is that the only work that differs depending on the product is the classification work, so there is little variation in quality between products. Finally, high-quality products can be obtained because they can be manufactured in a stable quality range through mass continuous production.
The present invention has great industrial value because it can solve all of the conventional problems.The above description is based on the case where the present invention is applied to the production of a thick-film multilayer wiring board. However, it is clear that the four inventions of the present invention can be applied to the production of multilayer wiring boards, such as printed boards or thin film circuit boards, using other techniques, and the effects of the present invention will not be diminished in the slightest in that case. 〇Also, in the embodiment of the present invention, the method of separating or cutting by chemical etching and laser beam has been explained, but the method is not limited to this method.
Any other method of cutting the conductor can be used.Furthermore, although the present invention has been described using a wiring board with two conductor layers, the present invention can be applied even if a conductor layer is added. It goes without saying that the standard wiring patterns of each layer are almost linear in the above embodiments, but the present invention is not limited to such a shape, but can be any shape, and can be applied to any desired shape. Circuit connections can be realized by a standard wiring pattern on the first layer, a standard wiring pattern on the second layer, and selective separation of interlayer connections between the first and second layers.

[Brief explanation of the drawing]

Figure 1 is a wiring diagram given as an example, and Figures 2 to 5 illustrate the process of manufacturing a multilayer wiring board by a conventional method.A is a plan view, and B is a cross-sectional view in each figure (AO)A-N. shows.

Claims (1)

[Claims] 1. A step of forming a layer of a wiring conductor on a substrate, a step of forming an insulating layer having at least an exposure opening that exposes a plurality of predetermined portions of the wiring conductor over substantially the entire width of the conductor, and A method for manufacturing a multilayer wiring board, comprising the step of selectively removing the predetermined portion of the wiring conductor that is exposed.