JPH0519319B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a multilayer printed wiring board used in various electronic devices and used to mount electronic components.

(Prior art) In general, electronic component standards for printed wiring boards assume a basic grid (usually 2.54 mm), which is a matrix-like grid with fixed intervals, and an auxiliary grid, which is divided into equal parts. Through-holes are provided at grid positions to mount electronic components such as ICs, and necessary wiring is provided at auxiliary grid positions. As electronic devices have become more sophisticated in recent years, there has been an increasing demand for higher density in multilayer printed wiring boards. Unused via holes are commonly used.

This via hole for non-component mounting is provided in an auxiliary grid position different from the basic grid, so in order not to interfere with wiring at other auxiliary grid positions, the diameter is smaller than that of the through hole for component mounting. Therefore, the cutting resistance during drilling of this via hole is greater than that of a through hole for mounting components, resulting in a decrease in machinability. This is because machinability generally decreases as the diameter of the through hole becomes smaller.

Around the through-hole connection portion of the inner layer pattern, the outer layer base material and the inner layer pattern peel off due to cutting resistance during drilling, although there are differences in degree. The degree of this peeling increases as the machinability decreases. Therefore, in a via hole with a small diameter, the peeling is more likely to occur than in a through hole for mounting components due to decreased machinability.

In particular, when a micro-diameter via hole penetrates a wide pattern (usually called a solid pattern) such as an inner layer power supply pattern or an inner layer ground pattern and is connected in an inner layer, the The adhesion between the prepreg serving as the outer layer base material and the inner layer pattern is weak, and the above peeling is likely to occur. This difference in adhesion is due to the fact that in the latter case, the prepreg adheres more strongly to the exposed resin part of the base material around the land pattern than to the copper surface of the inner layer base material. This is due to improved sexual performance.

By the way, the reason why the prepreg adheres more strongly to the base resin part than to the copper surface of the inner layer base material is as follows. Physically, since electrolytic copper foil is generally used as the copper foil for the base material, the resin part of the base material exposed by removing the copper foil has a surface area that is smaller than that of the copper surface that has been subjected to treatments such as polishing and oxidation. The roughness is quite high. Furthermore, from a chemical standpoint, the adhesion between resins is considerably stronger than the adhesion between resin and copper (copper oxide).

The peeling appears as an appearance defect called haloing. This haloing is a common method in which an oxide film is formed on the copper surface of the base material in order to improve the adhesion strength when the copper surface of the base material and the prepreg are brought into close contact with each other in the manufacturing process of multilayer printed wiring boards. However, in this method, peeling between the outer layer base material and the inner layer pattern occurs around the through hole connection portion of the inner layer pattern,
When acid, etc. seeps into the gap during pre-plating treatment, the oxide film partially dissolves and the area appears whitish, an appearance defect that occurs due to the deterioration of insulation resistance. This may cause defects such as increased peeling between the outer layer substrate and the inner layer pattern, and cracks in through-hole plating.

Conventionally, no measures have been taken to deal with only the haloing that occurs around the connection portion of the inner layer solid pattern to the via hole. To explain this conventional situation with reference to FIGS. 8 and 9, the via hole 22 for non-component mounting formed at the auxiliary grid position on the board surface has no boundary with the inner layer pattern 25, which is a solid pattern. They are directly and completely connected. That is, the multilayer printed wiring board 21 does not have a pattern missing part around the connection part 28, and no means was taken to prevent the inner layer pattern 25 and the outer layer base material 30 from peeling around the connection part 28. be.

As a countermeasure for this, the applicant and others previously filed a patent application in 1983.
In No.-282608, we proposed the multilayer printed wiring board described below. This multilayer printed wiring board is shown in Figure 10~
To explain with reference to FIG. 12, a pattern missing portion 43 is formed around a connecting portion 48 of the inner layer pattern 45, which is a solid pattern, to a non-component mounting via hole 42 formed at an auxiliary grid position on the board surface. This is a multilayer printed wiring board 41 characterized in that the pattern missing portion 43 is formed to form an inner layer land portion 47 and an inner layer land portion 47.
This shape allows formation of a connection pattern 46 that electrically connects the inner layer pattern 45 and the inner layer pattern 45 . In such a multilayer printed wiring board 41, in the pattern missing portion 43, the prepreg 50a and the exposed base resin portion 51a are different from the prepreg 50.
a and the inner layer pattern 45, this strong adhesion improves the adhesion between the prepreg 50a and the inner layer land portion 47, and the outer layer base material 50 formed by curing the prepreg 50a. Separation between the inner layer land portion 47 and the inner layer land portion 47 is less likely to occur, and haloing is suppressed.

However, in this multilayer printed wiring board 41, the connection pattern 46 is
When the width (the distance between the two pattern missing parts 43 sandwiching the connection pattern 46) is increased, the haloing penetrates the connection pattern 46 and the inner layer pattern 45
It may spread to. There are two possible causes of this phenomenon: First of all, if the connection pattern 46 is wide, the prepreg 50a in the pattern missing part 43 and the exposed base resin part 5
Prepreg 50a due to strong adhesion with 1a
This means that the improvement in adhesion between the connection pattern 46 and the connection pattern 46 is weaker at the center of the connection pattern 46, and the second
Second, stress during drilling tends to concentrate on the connection pattern 46 due to the formation of the pattern missing portion 43.

(Problems to be solved by the invention) The present invention has been made in view of the above-mentioned circumstances.
The problem to be solved is haloing around the connection area of the inner layer solid pattern with the non-component mounting via hole formed at the auxiliary grid position on the board surface. A pattern missing part is formed around the connecting part of the inner layer solid pattern to the via hole formed at the auxiliary grid position on the substrate surface, and this pattern missing part forms an electrical connection between the inner layer land part and this and the inner layer pattern. In a multilayer printed wiring board on which a connection pattern is formed, the connection pattern may penetrate from the inner layer land part through the connection pattern, and the inner layer pattern may penetrate through the connection pattern from the inner layer land, which occurs only when the width of the connection pattern (the distance between the two missing pattern parts sandwiching the connection pattern) is wide. It is a haloing that spreads into the pattern.

The object of the present invention is to connect the inner layer land portion and connection pattern formed around the connection portion of the inner layer solid pattern to the non-component mounting via hole formed at the auxiliary grid position on the board surface, and the outer layer base plate. The object of the present invention is to provide a multilayer printed wiring board that has improved adhesion to the prepreg material and suppresses the occurrence of haloing in the inner layer land portions and connection patterns.

(Means for Solving the Problems) The means taken by the present invention to solve the above problems are as follows: is formed, an inner layer land portion 7 is formed in the via hole 2, and an inner layer pattern 5 is formed around the inner layer land portion 7 on the same layer as the inner layer land portion 7. 7 and the inner layer pattern 5 surrounding it, there is a layer 2 that electrically connects them.
A pattern missing portion 3 is formed by leaving more than one connection pattern 8, and a pattern removal portion 4 is formed outside the connection pattern 8 on the inner layer pattern 5 and is separated from the connection pattern 8 and the pattern missing portion 3. is formed, and the interval between the inner layer land portion 7 and the outer periphery of the pattern removed portion 4 is equal to or less than the basic lattice, and the pattern missing portion 3 and the pattern removed portion 4 are formed in an arc shape concentric with the inner layer land portion 7, Furthermore, the multilayer printed wiring board is characterized in that the connection pattern 6 is located within a fan shape formed by the arc portion constituting the pattern removal section 4 and the center of the inner layer land section 7.

Next, the means of the present invention will be explained in more detail with reference to FIGS. 1 to 3.

FIG. 1 shows one of the multilayer printed wiring boards according to the present invention.
FIG. 2 and FIG. 3 are cross-sectional views of the - line part and - line part of FIG. 1, respectively.

In the multilayer printed wiring board 1 shown in FIG. 1, non-component mounting via holes 2 formed at auxiliary grid positions on the board surface are connected to an inner layer pattern 5 which is a solid pattern. A pattern missing portion 3 is formed around the connecting portion 8 between the via hole 2 and the inner layer land portion 7.
A connection pattern 6 is formed to electrically connect the inner layer land 7 and the inner layer pattern 5, and is further separated from the connection pattern 6 and the pattern missing portion 3 on the outside of the connection pattern 6 on the inner layer pattern 5. It is characterized in that a pattern removal section 4 is formed.

The pattern missing portion 3 and pattern removed portion 4 of this multilayer printed wiring board are, for example, inner layer land portions 7.
The connection pattern 6 is located within a sector formed by the arc portion forming the pattern removal portion 4 and the center of the inner layer land portion 7. Further, the distance between the inner layer land portion 7 and the outer periphery of the pattern removal portion 4 which is the largest distance from the inner layer land portion 7 is, for example, equal to or less than the basic lattice spacing. The specific shapes of the pattern missing portions 3 and pattern removal portions 4 include fan shapes as shown in FIG. 4, as well as the shapes shown in FIG. Or a fan shape as shown in Figure 6,
Various shapes shown in FIG. 7, in which the shapes of the pattern missing portion 3 and the pattern removing portion 4 in FIG. 6 are changed, are effective. Also, the hole diameter of via hole 2 is, for example,
The diameter is 0.7 mm or less.

(Actions of the Invention) By adopting the above-mentioned means, the present invention has the following effects.

In the pattern missing part 3 formed around the connection part 8 with the non-component mounting via hole 2 formed at the auxiliary grid position on the board surface of the inner layer pattern 4, which is a solid pattern, the prepreg 10a and the exposed base resin As described in the "Prior Art" section, the portion 11a adheres more strongly than the prepreg 10a and the inner layer pattern 5, and this strong adhesion causes the prepreg 10a to adhere to the inner layer land 7 and the connection pattern 6. Prepreg 10 improves adhesion
Outer layer base material 1 formed by curing a
0 and the inner layer land portion 7 and the connection pattern 6, suppressing haloing in the inner layer land portion 7 and the connection pattern 6, and preventing similar peeling in the pattern removal portion 4 formed on the outside of the connection pattern 6. The strong adhesion further improves the adhesion between the prepreg 10a and the connection pattern 6, makes peeling between the outer layer base material 10 formed by curing the prepreg 10a and the connection pattern 6 more difficult to occur, and improves the adhesion between the prepreg 10a and the connection pattern 6. This suppresses the haloing that penetrates the connection pattern 6 from the portion 7 and spreads to the inner layer solid pattern 5.

Especially when the hole diameter of via hole 2 is 0.5 mm or less,
The measures taken by the present invention have a remarkable effect and suppress haloing.

Furthermore, when the connection patterns 6 are formed at at least two locations, the reliability of the electrical connection between the via hole 2 and the inner layer pattern 5 does not deteriorate due to hole misalignment or the like.

Further, since the distance between the inner layer land portion 7 and the outer periphery of the pattern removed portion 4 having the largest distance is equal to or less than the basic lattice spacing, the shielding effect of the inner layer pattern 5 is not reduced.

Further, the pattern missing portion 3 and the pattern removal portion 4 are formed by an arc portion formed concentrically with the center of the inner layer land portion 7, and the connection pattern 6 is formed between the arc portion forming the pattern removal portion 4 and the inner layer land portion 7. Since the pattern removal portion 4 is located within the fan shape formed by the center of the pattern removal portion 4, the effect of improving the adhesion between the prepreg 10a and the connection pattern 6 by forming the pattern removal portion 4 is increased.

Next, the present invention will be explained in detail using examples.

(Example) Example 1 The multilayer printed wiring board 1 has an 8-layer structure in which a power supply pattern or a ground pattern, each of which is a solid pattern, is provided on the second and seventh layers, and the solid pattern portion is provided with an auxiliary pattern on the board surface. Of the via holes 2 for non-component mounting with a hole diameter of 0.4 mm formed at the grid positions, 64 holes are connected, and the pattern shown in Figure 4 is missing around the connection part 8 with the via hole 2 in the solid pattern part. It was manufactured by forming a portion 3 and a pattern removal portion 4.

Multilayer printed wiring board 1 produced in this way
The harrowing of the 264 via holes was evaluated. The evaluation was performed by polishing and removing the patterns of the first and eighth layers and a part of the outer layer base material 10 between the first and second layers and between the seventh and eighth layers.
Regarding the haloing that occurred around the connection part 8 with the via hole 2 of the layer ground pattern, the width (distance from the connection part 8) was measured using a 100x microscope.

As a result, 10 haloings with a width of 0.05 mm or more and less than 0.1 mm occurred, and no haloing with a width of 0.1 mm or more occurred.

Example 2 In Example 1, the hole diameter of via hole 2 was
It was set to 0.7mm. The multilayer printed wiring board 1 thus produced was evaluated for haloing in the same manner as in Example 1. As a result, the width is 0.05mm or more, 0.1
Haloing of less than mm occurred in 4 places,
No haloing of 0.1 mm or more occurred.

Example 3 In Example 1, the pattern missing portion 3 had the shape shown in FIG. The thus produced multilayer printed wiring board 1 was evaluated for haloing in the same manner as in Example 1. As a result, six haloings with a width of 0.05 mm or more and less than 0.1 mm occurred, and no haloing with a width of 0.1 mm or more occurred.

Comparative Example 1 In Example 1, the pattern removal portion 4 was not formed. The thus produced multilayer printed wiring board 41 was evaluated for haloing in the same manner as in Example 1. As a result, there were 34 haloings with a width of 0.5 mm or more and less than 0.1 mm, and 10 haloings with a width of 0.1 mm or more, of which 2 went up to connection pattern 6, 4 went through connection pattern 6, It had spread to inner layer pattern 5.

(Effects of the Invention) As detailed above, in the present invention, as exemplified in each of the above embodiments, "a via with a hole diameter of 0.7 mm or less that is not used for component mounting is provided at the auxiliary grid position on the board surface. A multilayer printed wiring board 1 in which a hole 2 is formed, an inner layer land portion 7 is formed in the via hole 2, and an inner layer pattern 5 is formed around the inner layer land portion 7 on the same layer, the inner layer 2 is provided between the land portion 7 and the inner layer pattern 5 surrounding it to electrically connect them.
The pattern missing portion 3 is formed by leaving more than one connection pattern 8, and a pattern removal portion 4 is formed outside the connection pattern 8 on the inner layer pattern 5, which is separated from the connection pattern 8 and the pattern missing portion 3. is formed, and the interval between the inner layer land portion 7 and the outer periphery of the pattern removed portion 4 is equal to or less than the basic lattice, and the pattern missing portion 3 and the pattern removed portion 4 are formed in an arc shape concentric with the inner layer land portion 7, Moreover, the multilayer printed wiring board is characterized in that the connection pattern 6 is located within a fan shape formed by the arc portion constituting the pattern removal portion 4 and the center of the inner layer land portion 7. As a result, in the pattern missing portion 3 and the pattern removal portion 4, the prepreg 10a serving as the outer layer base material 10 and the exposed base resin portion 11a serving as the inner layer base material 11 are in close contact with each other, so that the prepreg 9a and the inner layer land portion 7 and Connection pattern 6
The adhesion between the outer layer base material 10 and the inner layer land portion 7 and the connection pattern 6 is improved, and peeling between the outer layer base material 10 and the inner layer land portion 7 and the connection pattern 6 is less likely to occur. This makes it possible to suppress the spread of haloing.

Further, since the distance between the inner layer land portion 7 and the outer periphery of the pattern removed portion 4 having the largest distance is equal to or less than the basic lattice spacing, the shielding effect of the inner layer pattern 5 is not reduced.

Further, the pattern missing portion 3 and the pattern removal portion 4 are formed by an arc portion formed concentrically with the center of the inner layer land portion 7, and the connection pattern 6 is formed between the arc portion forming the pattern removal portion 4 and the inner layer land portion 7.
Since the pattern removal portion 4 is located within the fan shape formed by the center of the pattern removal portion 4, the effect of improving the adhesion between the prepreg 10a and the connection pattern 6 by forming the pattern removal portion 4 is increased.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of a multilayer printed wiring board according to the present invention, FIG. 2 is a sectional view taken along the line - in FIG. 1, and FIG. 3 is a cross sectional view taken along the line - in FIG. 1. 4 to 7 are plan views showing the pattern of the X portion in FIG. 1. FIG. 8 is a perspective view of a partially cut away part of a conventional multilayer printed wiring board, and FIG. 9 is a - of FIG. 8 corresponding to FIG. 2.
It is a sectional view of a line part. FIG. 10 is a perspective view of a partially cut away multilayer printed wiring board proposed earlier by the present applicant, FIG. 11 is a cross-sectional view of the - line part in FIG. FIG. 12 is a plan view showing the pattern of the Y portion in FIG. 10. Explanation of symbols, 1...Multilayer printed wiring board, 2...
... Via hole, 3 ... Pattern missing part, 4 ...
pattern removal part, 5...inner layer pattern (connected to via hole 2), 6... connection pattern, 7...
...Inner layer land part, 8...Connection part, 9...Inner layer pattern (not connected to via hole 2), 10...
Outer layer base material, 11...Inner layer base material.

Claims (1)

[Claims] 1. A via hole 2 with a hole diameter of 0.7 mm or less, which is not used for component mounting, is formed at the auxiliary grid position on the board surface, and an inner layer land portion 7 is formed in this via hole 2. This is a multilayer printed wiring board 1 in which an inner layer pattern 5 is formed around the same layer as the inner layer land portion 7, and the inner layer pattern 5 is electrically connected between the inner layer land portion 7 and the inner layer pattern 5 surrounding the inner layer land portion 7. Connect 2
A pattern missing portion 3 is formed by leaving more than one connection pattern 8, and a pattern removal portion 4 is formed outside the connection pattern 8 on the inner layer pattern 5 and is separated from the connection pattern 8 and the pattern missing portion 3. is formed, and the interval between the inner layer land portion 7 and the outer periphery of the pattern removed portion 4 is equal to or less than the basic lattice, and the pattern missing portion 3 and the pattern removed portion 4 are formed in an arc shape concentric with the inner layer land portion 7, Furthermore, the multilayer printed wiring board is characterized in that the connection pattern 6 is located within a fan shape formed by the arc portion constituting the pattern removal portion 4 and the center of the inner layer land portion 7.