JPH04162593A - Drilling through multilayer printed wiring board and formation of land pattern - Google Patents

Abstract

PURPOSE:To provide a longer life to a drill which is used for drilling of a multilayer printed wiring board by a method wherein when forming land patterns on internal layer pattern-formed substrates which constitute the multilayer printed wiring board, only the land patterns that are connected to wiring patterns are formed, and drilling is performed after laminate-molding of substrates for internal layer use and substrates for external layer use with prepregs put between the substrates for internal layer use and external layer use. CONSTITUTION:On internal layer pattern-formed substrates 10 which constitute a multilayer printed wiring board 14 which is not yet subjected to drilling, only such land patterns 11 as are connected to wiring patterns 12 are formed at the places corresponding to the places where through holes 9 are formed. When drilling the multilayer printed wiring board 14 for the through holes, the holes are made with a drill 15, with the drill 15 passing through a copper foil.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for drilling holes in a multilayer printed wiring board and a method for forming a land pattern.

[Prior art] As electronic devices become smaller and more densely packaged, printed wiring boards are becoming more densely packed. A multilayer printed wiring board with this technology has been put into practical use. Through holes are used for conduction between the inner and outer layers of a multilayer printed wiring board.

On the other hand, in recent years, printed wiring boards have been designed using ComputerA.
This is often done using a computer-aided design (CAD) system. The printed wiring board is designed using the CAD system in the following steps.

■Create a pin table (shown in FIG. 4) that combines the lands set for each layer regarding component holes necessary for component mounting.

■Place the components to be mounted externally and assign the specified data of the pin table to all the component holes.

■Lands are formed at the positions where through holes are formed in all layers, including the outer and inner layers. Taking the case of a 6-layer board as an example, the fifth
As shown in the figure, when the runt 2a is formed on the component surface 1 of the first layer (2), the inner layer pattern surface 3 of the second layer (2), the power supply (V CC) surface 4 of the third layer (2), and the fourth layer (2) Lands 2a, 2b, and 2c are automatically formed on the ground (GND) surface 5 of , the inner layer pattern surface 6 of the fifth layer V, and the solder surface 7 of the sixth layer (2). V
The lands 2c formed on the CC plane 4 and the GND plane 5 are formed in a pattern opposite to the other lands 2a' and 2b.

(2) Necessary wiring patterns 8 are formed for all layers (FIG. 6).

Then, pattern data for each layer is created based on the design drawing created as described above, and a pattern film for photoetching is created. Then, a conductor pattern is formed on each layer using the patterned film. Therefore, as shown in FIG. 2, the inner layer pattern-formed substrate 10 is formed with runts 2b, which were provided as marks for detouring through holes during the wiring design work, and are not connected to the wiring pattern 12 and are ultimately There are many unnecessary isolated land patterns 13.

[Problems to be Solved by the Invention] The isolated runt pattern 13 formed on the inner pattern-formed substrate 10 does not adversely affect the performance of the multilayer printed wiring board. However, as shown in FIG.
1 or the isolated land pattern 13. That is, the number of copper foil layers (runt patterns) that the drill must penetrate during drilling increases.

Penetrating the copper foil with a drill places an extra burden on the drill compared to penetrating the insulation layer, so if the copper foil is penetrated many times, the drill will be easily damaged and the drill will need to be replaced sooner. There is a problem in that it leads to an increase in manufacturing costs.

Particularly in recent years, with the increase in the density of wiring, the number of through holes formed in multilayer printed wiring boards has increased, and the number of through holes has increased. ~Tens of thousands of through holes are formed. Since drilling is performed by stacking multiple multilayer printed wiring boards, it is not possible to drill all the through holes with one drill in a multilayer printed wiring board with many through holes. The drill will need to be replaced. When this drill is replaced frequently, work efficiency decreases by the amount of time required.

Also, the smaller the diameter of the drill used for drilling, the more likely it is to be damaged, which means that the drill needs to be replaced sooner. Therefore, if an unnecessary land pattern is present on the inner layer pattern forming substrate, the above-mentioned problem will be exacerbated. It becomes noticeable.

The present invention has been made in view of the above problems, and includes:
The first object is to provide a method for drilling holes in a multilayer printed wiring board that can extend the life of the drill used in the drilling process for forming through holes in the multilayer printed wiring board.

A second object is to provide a land pattern forming method suitable for carrying out the above-described hole-drilling method.

[Means for Solving the Problem] In order to achieve the first object, in the invention according to the first claim, when a land pattern is formed on an inner layer pattern forming substrate constituting a multilayer printed wiring board, the wiring pattern is Only the land patterns to be connected were formed, and the substrates for the inner layer and the outer layer were laminated and molded with prepreg sandwiched between them, and then holes were punched.

Further, in order to achieve the second object, in the invention described in claim 2, the conductor pattern design of the multilayer printed wiring board is performed by Computer Aided Design (
(CAD) system, first create lands at all positions where through holes will be formed, then conduct wiring work, and then remove lands on the inner layer pattern surface that are not connected to the wiring pattern. The land data and the wiring data were deleted, and a pattern film created based on the subsequent data was used to form a pattern on the inner layer pattern forming substrate.

[Function] In the invention described in the first claim, since there is no unnecessary land pattern on the inner layer pattern forming substrate constituting the multilayer printed wiring board, when drilling a hole in the multilayer printed wiring board, l" l) The frequency of penetrating the copper foil with the drill is significantly lower than in the past.Therefore, the drill becomes less painful, extends the life of the drill, and increases the number of holes that can be drilled with one drill.

Further, in the second aspect of the invention, the conductor pattern of the multilayer printed wiring board is designed using a CAD system. At the initial stage of design, lands are formed at all positions corresponding to through holes on the component surface, inner layer pattern surface, etc. of each layer constituting the multilayer printed wiring board. Then, after the wiring work is performed, by performing an isolated land deletion operation, lands that are not connected to the wiring pattern among the lands on the inner layer pattern surface are automatically deleted based on the land data and wiring data stored in the CAD system. will be deleted. Since a pattern film is created based on this data, isolated land patterns are not formed on the inner layer pattern forming substrate, but only land patterns connected to wiring patterns are formed.

[Example] Hereinafter, an example in which the present invention is embodied in a 6-layer board will be described as follows.
This will be explained according to Figure 6. Incidentally, the same parts as those in the prior art are given the same reference numerals and detailed explanations will be omitted.

A multilayer printed wiring board is formed by multilayer lamination molding in the same way as in the past, with prepregs sandwiched between an outer layer substrate and an inner layer substrate, and between the inner layer substrates. The difference from the conventional method is that an isolated land pattern is not formed on the inner pattern-formed substrate.

That is, conventionally, as shown in FIG. 2, the inner layer pattern-formed substrate 10 had not only land patterns 11 connected to the wiring patterns 12, but also a large number of isolated land patterns 13 not connected to the wiring patterns 12. . However, in this invention, as shown in FIG. 3, only the land pattern 11 connected to the wiring pattern 12 is present on the inner pattern-formed substrate 1o.

As shown in FIG. 1(a), the inner layer pattern formed substrate IO constituting the multilayer printed wiring board 14 before drilling
The land pattern 1 connected to the wiring pattern 12 is shown in FIG.
1 is present at a position corresponding to the formation position of through hole 9. Therefore, when drilling the through holes 9 in the multilayer printed wiring board 14, the number of times the drill 15 penetrates the copper foil to make the holes is limited to the necessary minimum. For example, when using the inner layer pattern forming substrate 1o of FIG. 2 in which the isolated land pattern 13 exists, the drill 1
The number of times the copper foil is penetrated is 21 times, but when the inner layer pattern formed substrate 1o of FIG. Therefore, the drill 15 is less likely to be damaged during drilling,
The life of the drill 15 is extended, the time for replacing the drill is delayed, and the cost of drilling is reduced. Furthermore, when drilling a large number of holes in the multilayer printed wiring board 14, it is not necessary to replace the trill or the number of times the trill needs to be replaced can be significantly reduced, improving work efficiency.

Next, a method for forming a land pattern on the inner pattern-formed substrate 10 will be described.

The design of the conductor pattern on the inner layer pattern forming board is done using Computer Aided Design as in the past.
(CAD) system. The design procedure is also the same as before. That is, first, a pin table 16 as shown in FIG. 4 is created.

Next, a component to be mounted externally is placed on the screen of the CAD system, and the position data of all the component holes is input, and predetermined data of the pin table is assigned to each component hole. Next, based on the data, the fifth
As shown in the figure, lands 2 are placed at positions corresponding to through-hole formation positions for all layers from the 1st layer to the 6th layer.
A to 2C are arranged. And this land 2a~2c
Wiring is performed for each layer based on.

Conventionally, a pattern film for photoetching is created based on the pattern data created in the work up to this point. Therefore, as shown in FIG. 2, a large number of isolated land patterns 13 are formed on the inner layer pattern-formed substrate 10. On the other hand, in the present invention, after the wiring is completed for each layer, the isolated land deletion operation is performed. This operation is performed based on a determination as to whether or not wiring data having the same position data as that of each land exists for each land.

The position data of each land is represented by one set of X coordinate data and Y coordinate data, and the wiring data is represented by two sets of X coordinate data and Y coordinate data each indicating the position of its end. Therefore, the fact that the wiring data has the same position data as the land position data means that the wiring is connected to the land. If there is no wiring data having the same position data, the land is determined to be an isolated land and is deleted.

By storing the program data for performing the above-mentioned work in the storage device of the CAD system, the CAD system automatically performs the work of comparing and determining the position data of each land and the wiring data. After the isolated lands are deleted, a pattern film for photoetching is created based on the pattern data. Therefore, by using this pattern film, only the land pattern 11 connected to the wiring pattern 12 is formed on the inner pattern-formed substrate 10, as shown in FIG.

Note that the present invention is not limited to the above embodiments,
As a method of forming only the land pattern 11 connected to the wiring pattern 12 on the inner layer pattern forming substrate 10,
A method may be adopted in which the conductor pattern is designed without creating isolated lands from the beginning.

[Effect of the invention] As detailed above, according to the invention described in the first claim,
Since there are no unnecessary lands on the inner layer pattern forming board, when drilling holes in multilayer printed wiring boards, the frequency of the drill penetrating the copper foil is significantly lower than in the past, making the drill less likely to cause damage. Longer life and more holes that can be drilled with one drill.

Further, according to the invention set forth in the second claim, a land pattern when implementing the invention set forth in the first claim can be easily created on the inner layer pattern forming substrate.

[Brief explanation of drawings]

FIG. 1(a) is a sectional view of a multilayer printed wiring board before drilling according to an embodiment of the present invention;
Figure (b) is a cross-sectional view of the multilayer printed wiring board after drilling, Figure 2 is a plan view of the inner layer pattern-formed board with isolated land patterns, and Figure 3 is a cross-sectional view of the multilayer printed wiring board after hole-drilling. FIG. 4 is a partial view of the pin table, and FIGS. 5 and 6 are C
FIG. 7 is a schematic perspective view showing the order of conductor pattern design by the AD system, and is a cross-sectional view of a multilayer printed wiring board after drilling in a conventional example.

Claims (2)

[Claims] 1. When forming the land pattern (11) on the inner layer pattern forming substrate (10) constituting the multilayer printed wiring board (14), only the land pattern (11) connected to the wiring pattern (12) is formed, and only the land pattern (11) for the inner layer and the outer layer is formed. A method for drilling holes in a multilayer printed wiring board, which comprises laminating and molding a board with prepreg sandwiched therebetween, and then drilling the board. 2. Comp for conductor pattern design of multilayer printed wiring board
This was done using a uterAided Design (CAD) system, first creating lands (2a to 2c) at all positions where through holes (9) will be formed, then wiring work, and then forming the inner layer pattern surface (3). land (2b)
Of these, the lands (
2b) based on land data and wiring data, and forming a pattern on an inner layer pattern forming substrate (10) using a pattern film created based on the subsequent data.