JPH05335742A - Multilayer interconnection board and interlayer connection method therefor - Google Patents

Abstract

PURPOSE:To improve the reliability of an interlayer connection, and to facilitate a change of the connection in a type of multilayer interconnection board in which an interlayer connection is effected by inserting a conductive pin into a through-hole formed in a multilayer interconnection board. CONSTITUTION:Substrate resin layers 1 surrounding a through-hole 2 are degenerated by dissolution or the like, which, in turn, causes patterns 3 to be relatively projected to the inside of the through-hole 2. Thereafter, a spring pin 6 is inserted into the through-hole 2, so that the pin comes into contact with the projections.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a front surface and a back surface of a substrate made of an insulating resin, or a multilayer wiring board having a conductive pattern inside the board in addition to the front surface and the back surface. The present invention relates to a multilayer wiring board in which continuity is secured between the wiring boards.

[0002]

2. Description of the Related Art The structure of a conventional multilayer wiring board is shown in FIG. In the figure, 1 is a substrate resin layer, 2 is a cylindrical through hole provided in the substrate resin layer, 3 is a pattern made of a conductive thin film provided inside the substrate resin layer 1, 4 is copper plating, and 5 is Noble metal plating, 6 is a spring pin. The through hole 2 is opened by a drill or the like after forming the pattern 3 inside the substrate resin layer 1, and the pattern 3 is exposed on the inner wall of the through hole 1 when opened. The ring-shaped copper plating 4 is raised in contact with the exposed pattern 3. Further, a precious metal plating 5 is applied to cover the surface of the copper plating 4. The spring pin 6 is inserted into the through hole 2 so as to be pressed against the precious metal plating 5.

The structure of the spring pin 6 is shown in FIG. Generally, the spring pin 6 is formed by processing a metal piece that can be elastically deformed to some extent into a plate shape and further bending the metal piece into a cylindrical shape. The features that can be seen in the concrete shape are that the ends of the metal pieces facing each other by bending work form a corrugated groove 6a, and that both ends 6b and 6c of the spring pin 6 are directed inward. It is folded and rounded. Such a spring pin 6 is generally used by inserting it into a hole having an inner diameter slightly smaller than the maximum diameter of the pin. When the spring pin 6 is inserted into the hole, the outer circumference of the spring pin 6 is pressed and the radius is reduced. At this time, the groove 6a becomes narrower as the radius decreases, which facilitates the deformation of the spring pin 6. The groove 6a has a wavy shape because when the spring pin 6 is inserted into the hole and the groove 6a becomes narrow, the wavy portion is fitted so that the wavy portion, that is, both sides of the groove 6a. This is to prevent the spring pin 6 from being deformed in the axial direction, that is, in the vertical direction in the drawing.

Another method has been known when the pattern to be connected is exposed on both surfaces of the substrate resin layer. This method will be described with reference to FIG. FIG. 10 is a cross-sectional view showing another conventional connection structure. In the figure, 7 is a conductive and solid connecting pin, and 8 is solder. Other,
The elements having the same reference numerals as those in FIG. 8 are the same as those in FIG. However, the point that the pattern 3 is exposed on both front and back surfaces of the substrate resin layer 1 is different from the structure shown in FIG.

In order to connect the patterns 3 on both front and back surfaces of the substrate resin layer 1 with such a structure, the following method has been adopted. First, the pattern 3 is formed on the substrate resin layer 1. After that, the through hole 2 is opened by a drill or the like (not shown). The inner diameter of this through hole 2 is
Unlike the conventional example described at the beginning, it is slightly larger than the outer diameter of the connecting pin 7. Then, the connection pin 7 is inserted into the through hole 2. At this time, since the connecting pin 7 may fall off from the through hole 2 if it is left as it is, the connecting pin 7 is supported by a jig (not shown), or an adhesive for temporary fixing is applied to the connecting pin 7 before the through hole 2. Prevent the connecting pin 7 from falling off by inserting it into the connector 2.
After that, pour the melted solder 8 around the connection pin 7,
The continuity between the pattern 3 on one side and the connection pin 7 is secured. Then, the substrate is turned over, and the pattern 3 and the connection pin 7 are soldered in the same manner.

[0006]

However, the above-mentioned conventional connection method has the following problems. First, in the method described at the beginning, the plating thickness of the copper plating inside the through hole 2 may be uneven. Therefore, there is a problem in that the contact pressure of the spring pin 6 with respect to the noble metal plating 5 cannot be uniformly adjusted depending on the position and number of patterns, the plating thickness, and the like. This may lead to a phenomenon in which, in an extreme case, the spring pin 6 does not come into contact with the noble metal plating 5 at a specific pattern at all, so that conduction cannot be established. Further, even if electrical continuity is obtained, contact pressure changes in the long term due to aging of material, particularly substrate resin layer 1, thermal expansion strain, or plastic deformation that occurs in the spring pin 6, causing poor electrical continuity. Possibility, long-term reliability was not satisfactory.

Further, in the method described below, an increase in the number of steps is inevitable due to the fixing of the connecting pin 7 and the soldering. Also, in order to use soldering, in order to disconnect the connection pin 7 again by disconnecting the connection pin 7 after completing the connection,
It took time and effort to remove the solder 8 from the surface of the pattern 3 and pull out the connection pin 7. Further, since the soldering process inevitably applies heat to the substrate resin layer 1, the number of connection processes may be limited.

[0008]

In order to solve the above-mentioned problems, in the present invention, the substrate resin layer is melted inside the through hole to enlarge the inner diameter of the through hole, and the pattern is formed inside the through hole. After projecting to the above, the projecting portion is plated, and then a spring pin corresponding to the enlarged inner diameter is inserted into the through hole.

[0009]

According to the method described above, the spring pin inserted into the through hole comes into contact with the pattern protruding into the through hole through the plating to secure the conduction.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a connection structure according to an embodiment of the present invention. In the drawings, the elements having the same reference numerals as those in the drawings for explaining the conventional technique are the same as those in the conventional art. In the connection structure according to FIG.
A major difference from the first conventional technique is that the pattern 3 projects inside the through hole 2. Hereinafter, steps for realizing such a structure will be described step by step.

First, as shown in FIG. 2, a through hole 2 is opened in the substrate. This perforation may be performed by cutting using a drill or the like (not shown) as in the prior art. At this time, the inner diameter of the through hole 2 is several tens of μm to 0.1 mm larger than the desired diameter.
Keep it small. However, the dimensional accuracy with respect to the inner diameter of the through hole 2 does not have to be high, so as long as it is a method capable of forming the through hole 2 in the substrate resin layer 1 and the pattern 3 collectively, as a method of punching , Various methods can be adopted.

Next, a solution is applied to the inside of the through hole 2 to dissolve the substrate resin layer 1 around the through hole 2,
Degenerate. The solution used here may be appropriately selected depending on the material of the substrate resin layer 1, but for the glass epoxy copper clad laminate which is the most common printed board, commercially available permanganate is used. It is preferred to use a salt. Such a solution is applied to the inside of the through hole 2 by, for example, a method of directly dropping it inside the through hole 2. Then, the substrate resin layer 1 around the through hole 2 is dissolved and degenerates, and the pattern 3 that is not dissolved is formed.
Project relatively inside the through hole 2.

At this time, the speed of degeneracy and the amount of degeneracy can be arbitrarily set depending on the concentration of the solution, the coating amount, the ambient atmospheric temperature, and the like. Regarding the amount of degeneracy, normally, about several tens of μm is sufficient even in consideration of nonuniformity of the amount of degeneracy within the same through hole 2 and expansion of the substrate resin layer 1. If this amount of shrinkage is too large, the spring pin 6
Fixing becomes incomplete, and if it is too small, the amount of protrusion of the pattern 3 into the through hole 2 may be insufficient.Therefore, consider the conditions of using the board to some extent and study the optimal amount of degeneracy. It is desirable to do.

However, conversely, by changing the outer diameter of the spring pin 6 inserted into the through hole 2, it is possible to relatively flexibly deal with the fluctuation of the amount of shrinkage. Therefore, it is advantageous to suppress the occurrence of dimensional defects by first making the inner diameter of the through hole 2 opened by cutting or the like a little smaller and making the amount of degeneration larger. Further, in this case, the amount of protrusion of the pattern 3 into the through hole 2 is inevitably large, so the contact area between the pattern 3 and the spring pin 6 is increased, and the contact resistance is reduced. Further, there is an advantage that the reliability of conduction can be improved. Also, when the number of layers of the board is large, that is, many patterns 3 are formed on one board.
Even if the two overlap, it is good to keep the amount of degeneracy large. This is because in the vicinity of the pattern 3, the dissolution liquid may not efficiently permeate due to the influence of the surface tension of the dissolution liquid, and the amount of degeneracy may be smaller than in other portions. Further, even when the interval between the patterns 3 is narrow, it is considered that the same phenomenon occurs and the degeneracy does not easily occur. Therefore, in general, it is desirable to allow a large amount of degeneracy for a substrate having a large number of layers of pattern 3. A state in which the substrate resin layer 1 is degenerated in this way is shown in FIG. In the figure, 3a is a protruding portion of the pattern 3 exposed inside the through hole 2 due to the contraction of the substrate resin layer 1.

After that, the solution remaining inside the through hole 2 is removed. The dissolution liquid may be removed in the step of cleaning the entire substrate, which is essential for manufacturing the substrate. After completely removing the dissolved solution, the spring pin 6 is inserted into the through hole 2 to obtain the conduction between the patterns 3 in the simplest form. That is, if the spring pin 6 having an outer diameter slightly larger than the inner diameter of the contracted through hole 2 is inserted into the through hole 2, the protruding portion 3a is crushed by the spring pin 6, and as shown in FIG. Then, the protrusion 3a and the spring pin 6 come into contact with each other over a wide range. At this time, the diameter of the spring pin 6 can change due to the elasticity of the spring pin 6 itself, so the allowable range for the selection of the diameter of the spring pin 6 is relatively wide. It is necessary to select a spring pin 6 with a diameter larger than the diameter of the hole 2 for a secure connection. In addition, if particularly high reliability is required for the connection due to design requirements or the like, the spring pin 6 may be inserted after the protrusion 3a is plated with the precious metal 5a.

Although the case where the pattern 3 is provided inside the substrate resin layer 1 has been described so far, the pattern 3 is provided on the surface of the substrate resin layer 1, that is, the second pattern in the prior art section. Even in the case described in the above, it becomes possible to secure the continuity in the same manner. FIG. 5 shows a state in which the through holes 2 are provided in the substrate on which the pattern 3 is provided on the surface of the substrate resin layer 1. Even in such a case, a cutting process may be used to provide the through hole 2, but it is desirable to take care so that the pattern 3 is not separated from the substrate resin layer 1 during cutting. Specifically, when cutting with a drill, apply a backing plate (not shown), which may be cut with the substrate and the substrate, to the surface opposite to the surface where the cutting is started, and the tip of the drill is patterned. It is necessary to devise such as distributing the load applied to 3. It is also effective to fix the substrate with a clamp (not shown) or the like to suppress chatter vibrations that tend to occur during cutting, and to adjust the cutting speed so as not to increase it too much.

After that, as in the first embodiment, a solution is applied to the inside of the through hole 2 to shrink the substrate resin layer 1 as shown in FIG. At this time, if the base resin layer 1 is relatively thick as shown in FIG. 6, that is, if the space between the patterns 3 is wide, the dissolution liquid remains relatively unaffected by the effect of surface tension and relatively quickly through-holes. It is thought that it permeates around 2. In this case, degeneration itself may be accelerated, and accordingly, a low-concentration solution is used, and the ambient temperature is lowered.
It is desirable to make adjustments such as suppressing the amount of the solution to be applied. Of course, as described above, the dissolution liquid is less susceptible to the influence of surface tension, but if the base resin layer 1 is relatively thick, the area to be degenerated, that is, the through hole.
Since the surface area of No. 2 is also increased, there is also a factor that increases the amount of the necessary solution. Therefore, in determining the actual degeneration condition, it is desired to effectively combine various conditions by experiments and the like.

Further, even in the substrate having the pattern 3 on both the inside and the surface of the base resin layer 1 as in the combination of the first and second embodiments, the base resin layer 1 as described above is also used. It goes without saying that the technology for degenerating is applicable. However, in such a case, there may be a case where the exposed pattern 3 is provided only on one surface of the base resin layer 1, that is, as shown in FIG. In such a case, it is desirable that the dissolution liquid does not adhere to the surface on the side where the exposed pattern 3 is not provided, that is, below the lowermost pattern 3 in FIG. Specifically, after filling a cylindrical pellet (not shown) having an outer diameter similar to the inner diameter of the through hole 2 into a portion where the dissolution liquid is not desired to be adhered, the dissolution liquid is dropped, and after the degeneration, the substrate is removed. There is a method in which the pellet is removed after washing to remove the solution. In such a case, in order to evenly distribute the solution to the corners of the through hole 2, the solution is supplied from a nozzle (not shown) having a diameter sufficiently smaller than the inner diameter of the through hole 2, such as an injection needle. It is desirable to devise such as. Further, in any of the embodiments, as in the case of the first embodiment, the reliability of conduction can be improved by plating the protruding portion of the pattern 3 with a noble metal.

[0019]

As described above, according to the present invention, copper plating or soldering can be omitted in the step of inserting the pin into the through hole of the multi-layer substrate to secure the conduction. Can be omitted and costs can be reduced. In addition, the contact area between the pattern and the pin is increased, and it is less likely to be affected by uneven plating thickness, so that the contact resistance is reduced and the connection reliability is improved. Furthermore, since it is not necessary to apply heat to the board, the work of reinserting the pin can be facilitated at the time of design change and the cost of design change can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state in which a through hole is provided on a substrate.

FIG. 3 is a cross-sectional view showing a state where the substrate resin layer 1 is degenerated.

FIG. 4 is an explanatory diagram showing a contact state between a pattern and a spring pin.

FIG. 5 is a cross-sectional view showing a state in which a through hole is provided in the substrate of the second embodiment.

FIG. 6 is a cross-sectional view showing a state where the substrate resin layer 1 of the second embodiment is degenerated.

FIG. 7 is a sectional view showing a third embodiment of the present invention.

FIG. 8 is a cross-sectional view showing a conventional connection method.

FIG. 9 is an explanatory diagram showing a structure of a spring pin.

FIG. 10 is a cross-sectional view showing another conventional connection method.

[Explanation of symbols]

 1 ... Base resin layer 2 ... Through hole 3 ... Pattern 3a ... Projection 6 ... Spring pin

Claims (4)

[Claims] 1. A through hole which penetrates between patterns of a multilayer wiring board having a plurality of conductive patterns is provided on a surface of a substrate made of an insulating member or inside the substrate, and an insulating material around the through hole is provided. An interlayer in a multilayer wiring board, characterized in that a member is contracted, and a pin having a diameter larger than that of the through hole before contraction is inserted to bring the pin into contact with the plurality of conductive patterns. How to connect. 2. The interlayer connecting method for a multilayer wiring board according to claim 1, wherein a pin whose diameter can be elastically changed is used as the pin. 3. A plurality of conductive members having a substrate made of an insulating member, a through hole penetrating the substrate, and a hole having a diameter smaller than that of the through hole and at least a part of which overlaps with the through hole. And a conductive pin penetrating the through hole and contacting at least a part of the plurality of conductive patterns. 4. The multilayer wiring board according to claim 3, wherein the pin is a pin whose diameter can be elastically changed.