JP2012151297A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problems in the past occurring when dealing with a trouble of solder defective caused by blast of air from a rear face side of a through hole, into which a lead of an electronic component is inserted, in the case where the air inside the through hole expands during flow soldering and the electronic component occupies the surface side of the through hole; the problems in the past are high cost due to a protrusion formed on a surface of the printed wiring board for lifting up the electronic component, and blast of air inside the through hole from the rear face when the through hole is occupied though an air vent port for discharging air trapped in a depression of a bottom of the electronic component is provided.SOLUTION: A communication route communicating with a through hole is formed for opening an internal space of the through hole to the atmospheric air even if an electronic component is firmly attached to a surface of a printed wiring board in such a way as to occupy the through hole.

Description

  The present invention relates to a printed wiring board in which an electronic component is mounted on the front surface side and a lead wire of the electronic component is soldered on the back surface side.

  In the conventional printed wiring board of this type, a foil-like material made of a conductive material such as copper foil is attached to the back surface, and the foil-like material is formed into a desired shape by etching or the like. And the circular part which solders the lead wire of an electronic component is provided in a part of the foil-like part, and the site | part called a land is formed. A through hole penetrating the printed wiring board is formed in a substantially central portion of the land.

  The electronic component is provided with a lead. When the lead is inserted into the through hole from the front surface side of the printed wiring board, the lead protrudes from the center of the land on the back surface side of the printed wiring board. In this state, flow soldering is performed by pouring the molten metal into a solder bath with the back surface facing downward. With this flow solder, the lead and the land are electrically connected via the solder.

  In the soldering process, the printed wiring board is heated. Then, the air inside the through hole expands. However, if the electronic component is in close contact with the surface of the printed wiring board and the surface side of the through hole is blocked, the expanded air escapes to the back side, and at that time, the solder intervening between the land and the lead Air vent holes may be formed. Then, troubles such as poor contact occur in the soldered portion due to aging.

  Therefore, in order to prevent such air holes from being formed in the solder, a plurality of protrusions are formed on the surface of the printed wiring board so that the electronic component does not adhere to the surface of the printed wiring board. There is known one in which the side is not blocked by an electronic component (for example, see Patent Document 1).

  Also, if the bottom of the electronic component is recessed and air is trapped in the recessed part, another air vent hole is formed in the printed wiring board so as to communicate with the recessed part, and the lead is inserted. It is known that even if the air in the hole and the air in the recessed portion expand, the air can pass through the air vent hole (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 2000-196215 (FIG. 2) Japanese Patent Laying-Open No. 2005-93665 (FIGS. 2 and 3)

  In the device described in Patent Document 1, a gap is ensured between the electronic component and the printed wiring board, so that the surface side of the through hole is not blocked. Therefore, even if the air in the through hole expands, air escapes not to the back surface side to be soldered but to the front surface side, so that no air escape hole is formed in the soldered portion. However, a protruding portion must be separately provided on the surface of the printed wiring board, resulting in a problem that the cost is increased due to an increase in man-hours.

  Moreover, in what was described in patent document 2, since it is only necessary to form the air vent hole similar to the through hole, the cost does not increase, but the bottom surface of the electronic component is flat and closes the surface side of the through hole. In this case, since the through hole does not communicate with the air vent hole, it is impossible to eliminate the possibility that a hole is formed in the solder when the air in the through hole expands.

  Then, this invention makes it a subject to provide the printed wiring board which can escape the air in a through-hole, without providing a protrusion on the surface in view of said problem.

  In order to solve the above problems, a printed wiring board according to the present invention has a through-hole into which a lead wire of an electronic component is inserted, and the lead wire is inserted into the through-hole from the front surface side and is attached to the back surface side. In the printed wiring board for soldering the lead wire to the land, the internal space of the through hole communicates with the through hole into which the lead wire of the electronic component that is in close contact with the surface side and closes the surface side of the through hole is inserted. It is characterized in that a communication passage that opens the air to the atmosphere is formed.

  According to the above configuration, when an electronic component having a shape that closes the surface side of the through-hole is mounted, the internal space of the through-hole passes through the communication path without forming a protrusion on the surface of the printed wiring board. Communicate with the atmosphere. For this reason, even if the air in the through hole expands, the air expanded through the communication path is released to the atmosphere, so that the pressure in the through hole does not increase.

  In addition, the communication path may be opened on the back side by making the through hole into a long hole shape, but in that case, the land may be cut by the communication path, and between the land and the lead. The amount of solder intervening in the solder may be reduced. In order to prevent a decrease in the amount of solder, the communication path may be prevented from opening on the back surface of the substrate.

  As is clear from the above description, the present invention communicates the through-hole into which the lead is inserted into the atmosphere with the electronic component mounted thereon, so that the air in the through-hole is land side even if flow soldering is performed. Therefore, no hole is formed in the solder through which air has escaped.

The figure which shows the structure of one embodiment of this invention The figure which shows the state before inserting an electronic component Diagram showing the flow of expanded air during soldering The figure which shows the state which provided the communication groove

  FIG. 1 shows a state in which a light emitting diode P as an electronic component is mounted on an example of a printed wiring board 1 according to the present invention. Reference numeral 2 denotes a communication path that communicates with a through hole 3 to be described later and extends to the outside of the light emitting diode P.

  Referring to FIG. 2, the through hole 3 through which the lead L of the light emitting diode P is inserted is machined by a drill. The through-hole 3 is provided at a position where the light-emitting diode P is mounted. At this time, a tooth tool such as a drill that forms the through-hole 3 is moved in the horizontal direction while penetrating the printed wiring board 1. A communication path 2 communicating with 3 is formed. Generally, since the drilling of the through hole 3 is performed by an NC-controlled machine tool, the communication path 2 is formed in the machining process for forming the through hole 3 only by changing the machining program of the machine tool. Can do.

  Referring to FIG. 3, when lead L is inserted into through hole 3 and light emitting diode P is mounted on the surface of printed wiring board 1, printed wiring board 1 is poured into the solder bath in this state, and printed wiring board 1. Solder the back side of A land 11 made of copper foil is deposited on the back surface of the printed wiring board 1, and the molten solder in the solder bath adheres to both the land 11 and the lead L to form a solder portion S. The lead L is electrically connected to the land 11. At the time of this soldering, the air in the through hole 3 is heated and expands. However, the expanded air is released to the atmosphere through the communication path 2, so that it is not ejected to the solder part S side.

  By the way, in the said embodiment, when forming the communicating path 2, the tooth tool which penetrated the printed wiring board 1 is moved to the horizontal direction as it is, and the communicating path 2 is formed, Therefore A part of land 11 is a tooth tool. Disconnected. If the remaining land 11 has a sufficiently large area, soldering can be performed without any problem. However, when cutting of the land 11 is not desired, the communication groove 4 is formed as a communication path as shown in FIG. You may make it not penetrate the back surface of the printed wiring board 1. FIG. In this case, the through-groove 4 may be formed in any way, but for example, grooving may be performed using a rotating tooth tool C for a slotter.

  In addition, this invention is not limited to an above-described form, You may add a various change in the range which does not deviate from the summary of this invention.

DESCRIPTION OF SYMBOLS 1 Printed wiring board 2 Communication path 3 Through-hole 4 Communication groove P Electronic component L Lead

Claims (2)

  In a printed wiring board comprising a through hole into which a lead wire of an electronic component is inserted, the lead wire is inserted from the front surface side into the through hole, and the lead wire is soldered to a land attached to the back surface side. It is characterized in that a communication path is formed that opens to the atmosphere inside the through hole in communication with the through hole into which the lead wire of the electronic component that closes the surface side and closes the surface side of the through hole is inserted. Printed wiring board.   The printed wiring board according to claim 1, wherein the communication path does not open on a back surface of the substrate.

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