JP2014232785A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board using a sleeve for a through hole, which can reduce manufacturing cost.SOLUTION: A printed wiring board comprises an insulating substrate 2, a plurality of wiring patterns and through holes 4a, 4b for establishing electrical connection among the plurality of wiring patterns. Each of the through holes 4a, 4b is composed of an open hole which pierces the insulating substrate 2 and a slit sleeve 5 where a slit is formed over the entire length and in a longer direction of a conductive sleeve body having a hollow cylindrical shape. The split sleeve 5 has a circle cross section having a diameter in an unloaded condition, which is larger than a diameter of a cross section of the open hole, and the split sleeve 5 is held by an inner periphery of the open hole by an elastic force of the split sleeve 5.

Description

  The present invention relates to a printed wiring board including an insulating layer and a plurality of conductor layers.

  The printed wiring board is provided with an insulating layer and a single-layer or multilayer conductor layer. The conductor layer is arranged on the surface or inside of the insulating layer and is a circuit (wiring pattern) for connecting various components to achieve a function designed according to the purpose. This wiring pattern is formed using a printing technique. In the printing technique, for example, there is a method (subtractive method) in which an unnecessary portion of copper foil is removed from a copper foil pasted on the entire surface of an insulating substrate as an insulating layer to leave a wiring portion. In this subtractive method, the circuit pattern is formed by covering the wiring pattern shape with a mask film that has been photographed and exposing it to a portion of the wiring pattern that is desired to remain as wiring, and then dissolving with a solvent. It is. Applications of printed wiring boards include surface mounting technology where chip components are fixed (mounted) on a substrate by soldering (mounting) to form an electronic circuit, or chip patterns are not used and wiring patterns are used as signal transmission paths And may be used as a high frequency circuit.

  In response to demands for miniaturization and high density integration of printed wiring boards, complex printed wiring boards having multiple (multiple) conductor layers have been developed. Through holes are used to electrically connect each conductor layer. In general, a through hole is formed of a conductive material (through a through hole formed perpendicular to a wiring pattern (that is, perpendicular to a printed wiring board) by a processing method such as laser processing, drilling, or etching. For example, copper plating). This through hole achieves electrical connection between a plurality of conductor layers. Production techniques suitable for mass production have been established for printed wiring boards, and in particular, through holes can be mass-produced at low cost using plating.

  On the other hand, when the production quantity is small, it is considered that plating is not performed for forming the through hole, and electrical connection is achieved using another conductive member. In recent years, a technique for forming a through hole by inserting a small and cylindrical member (sleeve) into a through hole for a through hole has been reported as a method for forming a through hole. As a method for fixing the sleeve in the through hole for the through hole, a method has been proposed in which a terminal having a spring property, which is a component different from the sleeve, is inserted into the sleeve and the sleeve is deformed and held.

  For example, in the sleeve disclosed in Japanese Patent Laid-Open No. 2005-116463, a press-fit terminal is introduced on the inner surface of the sleeve, and the contact pressure with the through hole of the printed wiring board is secured by the urging force of the press-fit terminal.

JP 2005-116463 A

  In a printed wiring board using a sleeve for a through hole, when the sleeve is fixed using another component as in the above technique, the number of components increases and it is difficult to reduce the manufacturing cost.

  Therefore, an object of the present invention is to provide a printed wiring board that can reduce the manufacturing cost in a printed wiring board that uses a sleeve for a through hole.

  For the purpose of solving the above problems, the present invention provides a printed wiring board including an insulating layer, a plurality of conductor layers, and a through hole that electrically connects the plurality of conductor layers. A split hole in which a slit extending over the entire length in a longitudinal direction is formed in a conductive sleeve body having a hollow cylindrical shape, and the split sleeve has a circular cross section in an unloaded state. The printed wiring board is characterized in that the diameter is larger than the diameter of the cross-section of the through hole and is held on the inner peripheral surface of the through hole by the elastic force of the split sleeve.

  The split sleeve may be made of an insulating material having elasticity and a conductive material formed on the surface of the insulating material.

  The conductive material may include solder plating, and the solder plating and the conductor layer may be joined by melting the solder plating by heating.

  The connection part of the said conductor layer and the said split sleeve may be joined by fusion | melting of thread solder or cream solder.

  The conductive material may include at least one of tin plating, copper plating, and solder plating.

  According to the present invention, it is possible to reduce the manufacturing cost in a printed wiring board using a sleeve for a through hole.

1 is a perspective view of a printed wiring board according to a first embodiment of the present invention. It is the elements on larger scale of the printed wiring board concerning a first embodiment of the present invention. It is X-X 'sectional drawing of the printed wiring board which concerns on 1st embodiment of this invention. It is a perspective view of the split sleeve which concerns on 1st embodiment of this invention. It is explanatory drawing which shows the elasticity of a split sleeve. It is explanatory drawing of the manufacturing process of a printed wiring board. It is explanatory drawing which inserts the sleeve which concerns on 1st embodiment of this invention in a through-hole.

  Hereinafter, a printed wiring board according to a first embodiment of the present invention will be described with reference to the drawings.

  1 is a perspective view of the printed wiring board according to the first embodiment of the present invention, FIG. 2 is a partially enlarged view of the printed wiring board of FIG. 1, and FIG. 3 is the printed wiring board of FIG. It is sectional drawing of XX '.

  The printed wiring board 1 includes an insulating substrate 2 as an insulating layer, a wiring pattern 3 as a conductive layer formed on the front and back surfaces of the insulating substrate 2, and a through-hole that electrically connects the wiring patterns 3 on the front and back surfaces. 4 is provided. The through hole 4 includes a through hole penetrating the insulating substrate 2 and a split sleeve 5 held on the inner peripheral surface of the through hole. The through hole 4 is used, for example, when the wirings of the wiring pattern 3 intersect with each other while being insulated. As shown in FIGS. 2 and 3, the through holes 4 a and 4 b and the wiring 3 b on the back surface of the insulating substrate 2 are electrically connected. As a result, the electric signal passing through the wiring pattern 3 on the front surface is transmitted from the through hole 4a to the wiring 3b on the back surface, further transmitted to the front surface wiring 3c via the through hole 4b, and intersects the wiring 3a while being insulated. Can be.

  As shown in FIGS. 4 and 5, the split sleeve 5 includes a conductive sleeve body 6 having a hollow cylindrical shape and a slit 7 formed over the entire length of the sleeve body 6 in the longitudinal direction. The sleeve body 6 is formed of a material having elasticity (spring property). By providing the slit 7 formed in the sleeve body 6, the split sleeve 5 can have an elastic force in the short direction perpendicular to the longitudinal direction. As a material of the split sleeve, phosphor bronze having both conductivity and elasticity (spring property) can be used. A split sleeve in which a conductive material (tin plating, copper plating) is formed on the surface of an insulating material having elasticity can also be used.

  In FIG. 5, the solid line shows the split sleeve 5 in an unloaded state, and the broken line shows the split sleeve 5 ′ deformed by applying a load in the short direction. The deformed split sleeve 5 'is subjected to a restoring force in the short direction to return to the unloaded split sleeve 5 by elastic force.

  The through hole of the through hole 4 has a cylindrical shape, and a cross section in the short direction perpendicular to the longitudinal direction is circular. Further, the split sleeve 5 is partially cut by the slit 7, but the cross section in the short direction is circular. The split sleeve 5 is formed such that the cross-sectional diameter in the short direction in a no-load state is slightly larger than the cross-sectional diameter of the through hole of the through hole 4. For this reason, in order to insert the split sleeve 5 into the through hole, it is necessary to deform the split sleeve 5 by applying a load so that the diameter of the cross section of the split sleeve 5 is smaller than the diameter of the cross section of the through hole. The split sleeve 5 is deformed in this manner and inserted into the through hole (FIG. 7), and the load is released after the insertion, so that the split sleeve 5 is self-held inside the through hole by the restoring force of the split sleeve 5 itself. .

  Next, a manufacturing process of a wiring pattern of the printed wiring board 1 having an insulating layer and two conductive layers on the front and back surfaces will be described.

  FIG. 6 is an explanatory diagram of a printed wiring board manufacturing process. First, an insulating substrate 2 having a copper foil as a conductive layer bonded to the entire surface is prepared on the front and back surfaces (FIG. 6A). Next, a through hole 8 for a through hole is processed at a predetermined position by using drilling or laser processing (FIG. 6B). In this state, the conductive layers on the front and back surfaces are still in an insulating state.

  In the conventional printed wiring board, after that, copper plating is formed in the through hole 8 for the through hole (inner peripheral surface) by the chemical copper plating technique, and further, the inside of the through hole 8 of the through hole is formed by electroplating. And copper plating is formed in the whole copper foil surface (FIG.6 (c)). Thereby, the conductive layers on the front surface and the back surface are electrically connected through the through holes. Next, the copper foil on the surface is etched to form a wiring pattern so as to obtain a circuit according to the purpose (FIG. 6D).

  In order to obtain a through-hole having high-quality conductivity, (1) the surface roughness of the hole surface is reduced, and the uncoated portion is eliminated. (2) Processes such as surface cleaning prior to plating using acid and alkaline cleaning solutions, and (3) optimization of plating conditions and equipment stability are required. Plating treatment can be carried out many times at once by using a plating agent in a plating treatment facility. For this reason, although the plating process is suitable for mass production, there is a possibility that the plating agent is wasted when it is produced in a small amount.

  Therefore, in the present invention, the split sleeve 5 is used in the through hole instead of plating. In this case, without proceeding to the plating process (FIG. 6C), the process proceeds to a process of forming a wiring pattern by etching the copper foil on the surface (FIG. 6E). Thereafter, a load is applied to the split sleeve 5 to be deformed and inserted into the through hole for the through hole, and the load is released from the split sleeve 5. The split sleeve 5 abuts on the inner peripheral surface of the through hole by its own restoring force and is held in the through hole (FIG. 6F).

  According to the embodiment of the present invention described above, the following operations and effects can be obtained.

(1) Since the split sleeve 5 includes a conductive sleeve body 6 having a hollow cylindrical shape and a slit 7 formed over the entire length in the longitudinal direction of the sleeve body 6, the split sleeve 5 is penetrated by its own restoring force. It can be held on the inner peripheral surface of the hole. For this reason, since the split sleeve 5 does not need to use another component for holding | maintaining on an internal peripheral surface, it is possible to reduce manufacturing cost.

(2) Since the through hole 4 can be formed without performing the plating process, it is possible to eliminate the waste of the plating agent in small-scale production.

  Next, a second embodiment of the present invention will be described.

  The split sleeve in this embodiment is made of an insulating material having elasticity and a conductive material formed on the surface of the insulating material, and solder plating is used as the conductive material. Other configurations of the printed wiring board of the present embodiment are the same as those of the first embodiment.

  The split sleeve is deformed by applying a load and inserted into the through hole for the through hole. By releasing the load from the split sleeve, the split sleeve comes into contact with the inner peripheral surface of the through hole by a restoring force and is held in the through hole. . In this held state, the solder plating and the wiring pattern (conductor layer) are joined by heating and melting the solder plating.

  As a method for heating and melting the solder plating, for example, there is a method in which a soldering iron is directly applied to the wiring pattern of the printed wiring board and the surface vicinity of the printed wiring board of the split sleeve, or a method in which the soldering iron is brought close. There is also a method of placing a printed wiring board in a heating furnace such as a reflow furnace maintained at a temperature at which the solder melts.

  According to the embodiment of the present invention described above, the following operations and effects can be obtained.

(1) The split sleeve is brought into contact with the inner peripheral surface of the through hole by a restoring force, and is held in the through hole, and in a multi-state, the solder plating of the split sleeve is heated and melted, whereby the split sleeve and the wiring pattern are separated. An electrical connection can be made reliably. Thereby, it is possible to obtain a highly reliable through hole.

(2) Since the split sleeve is held in the through hole by its own restoring force, it is not necessary to hold the split sleeve or separate parts to hold it until the solder plating is melted and solidified. is there. For this reason, it becomes possible to reduce the load of the operation | work which melts the solder plating of a split sleeve, and it is possible to reduce manufacturing cost.

  Next, another embodiment of the present invention will be described. In this embodiment, thread solder or cream solder is used for the connection portion between the wiring pattern (conductor layer) and the split sleeve.

  First, the split sleeve is inserted into the through hole for the through hole and held on the inner peripheral surface of the through hole by a restoring force. Next, thread solder or cream solder is added to the connection portion between the wiring pattern and the split sleeve. By heating in this state, the thread solder or cream solder is melted. Thus, the wiring pattern and the split sleeve are reliably electrically connected. The split sleeve can be composed of an insulating material having elasticity and a conductive material formed on the surface of the insulating material. As the conductive material, tin plating, copper plating, or solder plating is used. Can do.

  As mentioned above, although embodiment of this invention was described, embodiment described above does not limit the invention which concerns on a claim. In addition, it should be noted that not all combinations of features described in the embodiments are necessarily essential to the means for solving the problems of the invention.

1 Printed wiring board 2 Insulating substrate (insulating layer)
3 Wiring pattern (conductive layer)
4 Through hole 5 Split sleeve 6 Sleeve body 7 Slit 8 Through hole

Claims (5)

In a printed wiring board comprising an insulating layer, a plurality of conductor layers, and a through hole that electrically connects the plurality of conductor layers,
The through-hole is composed of a through-hole penetrating the insulating layer and a split sleeve in which a slit extending over the entire length in the longitudinal direction is formed in a conductive sleeve body having a hollow cylindrical shape,
The split sleeve is characterized in that a diameter of a circular cross section in an unloaded state is larger than a diameter of a cross section of the through hole, and is held on an inner peripheral surface of the through hole by an elastic force of the split sleeve. Printed wiring board.   2. The printed wiring board according to claim 1, wherein the split sleeve is made of an insulating material having elasticity and a conductive material formed on a surface of the insulating material. The conductive material includes solder plating,
The printed wiring board according to claim 2, wherein the solder plating and the conductor layer are joined by melting of the solder plating by heating.   The printed wiring board according to claim 2, wherein a connection portion between the conductor layer and the split sleeve is joined by melting of solder wire or cream solder.   The printed wiring board according to claim 4, wherein the conductive material includes at least one of tin plating, copper plating, and solder plating.

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