JP2005222770A - Connection structure of printed circuit board and connection method of printed circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connection structure of printed circuit boards with small electric terminal parts, capable of making high-density connection in an apparatus. <P>SOLUTION: In connecting the printed circuit boards, an adhesive sheet made of either thermoplastic resin or thermosetting resin is pinched between the electric terminal parts as connection parts. Here, the electric terminal parts of the printed circuit boards are heated and pressurized, and an adhesive is made to flow into air space formed by conductor circuits to bond each insulation material with the other of the printed circuit boards. With this, an interval between the conductor circuits of the electric terminal parts can be narrowed, and as a result, the electric terminal parts can be made smaller to allow connection of the high-density printed circuit boards. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a connection structure for connecting electrical terminals arranged on a printed circuit (electric circuit) board and a method for connecting the printed circuit board.

  As a method of connecting the terminal part of an electric circuit, a connection using a connector, a soldering method in which solder is reflowed to a conductor circuit of a terminal part of an electric circuit, and a terminal part of another electric circuit is bonded and heated. There is. By connecting and integrating a plurality of printed circuit boards by these methods, a printed circuit board having a complicated structure can be manufactured at a low cost.

  As an example of a method for connecting electrical terminals of a printed circuit board using a connector, an insulating intermediate member is fitted between two printed circuit boards, and a conductive metal fitting presses the conductive pattern of the printed circuit board. There is a method of making various electrical circuits using various printed circuit boards, and improving the yield of the printed circuit board material by using the electrical connector having a contact structure. (For example, see Patent Document 1)

In addition, as an example of a method of connecting the electric terminal portion of the printed circuit board by soldering, using a solder containing a substance that generates a gas at the time of melting, the generated gas breaks the oxide film on the solder surface, Since a new surface is exposed, there is a soldering connection method that eliminates the need for flux. (For example, see Patent Document 2)
Japanese Patent Laid-Open No. 05-266952 Japanese Patent Application Laid-Open No. 08-162753

FIG. 6 is a diagram illustrating an example of a printed circuit board connected by a connector. A connector 23 is fixed to the end of the conductor circuit 22 formed on the surface of the printed circuit board 21. By inserting the connector 24 joined to another printed circuit board into the connector 23, the printed circuit boards are electrically joined together.
FIG. 7 is a diagram illustrating an example of a connection portion of a printed circuit board circuit by soldering. A conductor circuit 22 is formed on the surface of the printed circuit board 21. The conductor circuit 22 extends to a terminal 25 which is a connection portion of the printed circuit board, and is not shown in the figure, but is soldered to a terminal of another printed circuit board similarly listed, and the circuit board 21 is other Electrically connected to the printed circuit board.

In recent years, circuit miniaturization has progressed in printed circuit boards, and portable communication devices such as mobile phones are required to be further miniaturized. Therefore, there is a demand for miniaturization and space saving in the connection part of printed circuit boards. It is increasing. On the other hand, in the connection structure of the printed circuit board electrical terminal portion using the conventional connector, the distance between the conductor circuits of the electrical terminal portion of the printed circuit board is limited due to the size of the connector itself and the restrictions on the distance between adjacent connection portions. There was a limit to narrowing.
On the other hand, in the connection of the printed circuit board by soldering, when the distance between the adjacent conductor circuits is small, when the solder layer is formed on the conductor circuit surface by reflow or when the solder is reheated, There is a risk that the solder may adhere between the two and the circuit may be short-circuited. In order to prevent this short circuit, it has been difficult to reduce the interval between the conductor circuits in the electric terminal portion.
In addition, it is necessary to precisely match the corresponding terminals of the printed circuit board to be connected, which is also a factor that hinders circuit miniaturization. Further, it is necessary to heat the electrical terminal portion to a temperature equal to or higher than the melting point of the solder at the time of connection, and there is a problem that the printed circuit board is easily damaged by heat.

  Therefore, the problem in the present invention is that the printed circuit board can reduce the interval between the conductor circuits of the electrical terminal portion of the printed circuit board and can reduce the size of the connection portion so that high-density wiring in the device is possible. It is to provide a connection structure for a substrate.

  In order to solve such a problem, the invention described in claim 1 is to form a plurality of conductor circuits coated with insulation except for an electrical connection portion on an insulating base material, and to electrically connect to other circuit boards. In the printed circuit board connection structure including the electrical terminal portions where the plurality of conductor circuits are exposed, an adhesive is narrowed to the opposing electrical terminal portions of the printed circuit board, and the electrical terminal portions are connected to each other. It is a connection structure of a printed circuit board.

  The invention described in claim 2 is characterized in that the conductor circuit of the electric terminal portion of at least one of the printed circuit boards is convex toward the conductor circuit side where the cross section of the conductor circuit is opposed. 1 is a connection structure of one printed circuit board.

  According to a third aspect of the present invention, in the conductor circuit of the electrical terminal portion of at least one of the printed circuit boards, the side of the conductor circuit on which the cross section of the conductor circuit is opposed is shorter than the side on the insulating substrate side. 2. The printed circuit board connection structure according to claim 1, wherein the printed circuit board connection structure is trapezoidal.

  Further, the invention described in claim 4 is characterized in that the adhesive narrowed on the insulating material surface of the electric terminal portion of one of the printed circuit boards and the insulating material surface of the electric terminal portion of the other printed circuit board is both insulated. 4. The printed circuit board connection structure according to claim 1, wherein the substrate surface is adhered.

  The invention described in claim 5 is the printed circuit board connection structure according to any one of claims 1 to 4, wherein the adhesive is a thermoplastic or thermosetting resin.

  In the invention described in claim 6, a plurality of conductor circuits which are insulated and coated except for an electrical connection portion are formed on an insulating substrate, and a plurality of conductor circuits for electrically connecting to another circuit board. In the method of connecting a printed circuit board having an exposed electric terminal part, a sheet-like adhesive is narrowed between the other electric terminal parts opposite to one electric terminal part, and then the adhesive is sandwiched between the electric terminals The printed circuit board connecting method is characterized in that the portions are joined by hot pressing.

  The invention described in claim 7 is characterized in that the sheet-like adhesive narrowed between the electric terminal portions is shaped so as to fit into the shape of the conductor circuit arranged in the electric terminal portions. The printed circuit board connection method according to claim 6.

  According to the printed circuit board connection structure of the present invention, in the conductor circuit of the electrical terminal portion of the printed circuit board, the adjoining generated by the solder flowing out of the conductor circuit during the solder reflow process or the reheating of the printed circuit board. It is possible to prevent a short circuit with the conducting circuit. Therefore, it is possible to reduce the distance between the conductor circuits of the electric terminal portions to which the printed circuit board is connected, thereby reducing the electric terminal portions and enabling high-density wiring in the device.

In addition, according to the printed circuit board connection method of the present invention, the adhesive for bonding the electric terminal portion can be easily mass-produced because it is in the form of a sheet, and the material cost compared to connector connection and solder connection. And processing costs are reduced. Moreover, the heating temperature at the time of adhesion can be set lower than the heating temperature at the time of soldering, and damage to the circuit board due to heat can be prevented.
Also, in recent years, the use of lead-free solder that does not contain lead has been increasing in consideration of the impact on the environment, but lead-free solder also has a problem of damaging the stainless steel solder bath in the flow soldering process, Usually, solder has not been completely replaced. Since the present invention does not use solder itself, the present invention is also effective for lead-free connection of printed circuit boards.

The present invention will be described in detail below.
1 and 2 are diagrams illustrating an example of a relationship between an electric terminal portion of two printed circuit boards facing each other and an adhesive sheet narrowed by the electric terminal portion.
In the printed circuit boards 11 and 12, a conductive circuit made of a conductive material is formed on an insulating base made of an insulating material by an etching method or the like, and each circuit board is connected to another circuit board. Electrical terminal portions 13 and 14 are provided as parts. Conductor circuits 15 and 16 having the same shape extending from the printed circuit boards 11 and 12 are formed on the opposing surfaces of the electrical terminal portions 13 and 14.

An adhesive sheet 17 made of a thermoplastic resin or a thermosetting resin is sandwiched between the two electric terminal portions 13 and 14. The adhesive sheet 17 is formed to have the uniform thickness and the dimensions of the electric terminal portions 13 and 14. Further, instead of the adhesive sheet 17, an adhesive layer may be formed by applying an adhesive made of a thermoplastic resin or a thermosetting resin to the surface of the electric terminal portion 14.
Alternatively, the adhesive sheet 17 may be previously formed in a shape that fits with the electric terminal portions 13 and 14, and the electric terminal portions 13 and 14 may be aligned using the adhesive sheet 17.

3 and 4 are cross-sectional views showing the relationship of the adhesive sheet 17 that joins the electric terminal portions 13 and 14.
The cross sections of the conductor circuits 15 and 16 are trapezoidal in which the sides on the side of the conductor circuit facing the electrical terminal portions 13 and 14 are shorter than the sides on the insulating base material side. Moreover, the shape of the cross section of the conductor circuits 15 and 16 may be an arc shape convex toward the opposing conductor circuit side. The conductor circuits 15 and 16 having a trapezoidal cross section can be formed by a plurality of etchings, for example. Details are described below.
First, a normal conductor circuit having a rectangular cross section is formed by the first etching. Further, etching is performed again with masking that covers a smaller area than the first etching. As a result, the side surface of the conductor circuit and the corner portion between the side surface and the surface where the insulating substrate is not in contact are cut away, and a conductor circuit having a trapezoidal cross section is formed.
The pressing force received by the electric terminal portions 13 and 14 is concentrated on the surfaces of the conductor circuits 15 and 16 that are the protruding portions of the electric terminal portions 13 and 14. Further, since the cross sections of the conductor circuits 15 and 16 are convex arcs or trapezoids on the conductor circuit side, the stress of the electric terminal portions 13 and 14 is concentrated and propagated in a smaller area. 17 can be divided.

FIG. 5 is a diagram illustrating a schematic method of bonding the electric terminal portion with an adhesive sheet.
The adhesive sheet 17 is disposed at a position narrowed by the electric terminal portions 13 and 14, and in this state, is heated simultaneously with the pressurization by the hot press (FIG. 5-a). The adhesive sheet 17 that has been heated and has increased fluidity is divided by the pressing force by pressurization and flows out into the gap 18 between the conductor circuits (FIG. 5B). The gap 18 is filled with the resin of the adhesive sheet 17 that has flowed out, and the printed circuit boards 11 and 12 are bonded to each other by bonding the resin to the insulating base material of the electric terminal portions 13 and 14 (FIG. 5-c).

Examples of the present invention are shown below.
A printed circuit board having an electrical terminal portion in which 20 copper conductor circuits of width 20 μm × length 15 mm × thickness 35 μm are arranged at intervals of 200 μm on an insulating base made of polyimide having a width of 10 mm × length of 20 mm × thickness of 25 μm. Two sheets were prepared. An adhesive sheet made of polyethylene resin, which is a thermoplastic adhesive having a thickness of 30 μm, molded to 10 mm × 20 mm was sandwiched between the electric terminal portions facing the surfaces having conductor circuits and pressed. In this state, while applying a pressing force of 0.1 MPa to the outer surface of the electric terminal portion, it was heated to 120 ° C. and held for 2 minutes, and then cooled to room temperature.
This printed circuit board has a width of 10 mm and a thickness of 120 μm, and is greatly reduced in size as compared with a connection part of a printed circuit board by conventional connector processing or soldering.

It is a schematic sectional drawing which shows an example of the connection structure of the printed circuit board of this invention. It is a schematic sectional drawing which shows an example of the connection structure of the printed circuit board of this invention. It is a schematic sectional drawing which shows an example of the connection structure of the printed circuit board of this invention. It is a schematic sectional drawing which shows an example of the connection structure of the printed circuit board of this invention. (A)-(c) It is a schematic sectional drawing which shows an example of each process used as the connection method of the printed circuit board of this invention. It is a schematic block diagram which shows an example of the connection part of the printed circuit board connected by the conventional connector. It is a schematic block diagram which shows an example of the connection part of the printed circuit board circuit by the conventional soldering.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11,12 ... Circuit board, 13, 14 ... Electrical terminal part, 15, 16 ... Conductor circuit, 17 ... Adhesive sheet

Claims (7)

In the connection structure of the printed circuit board including the electrical terminal portion in which the plurality of conductor circuits are formed on the insulating base material and the plurality of conductor circuits for electrical connection with other circuit boards are exposed,
A printed circuit board connection structure characterized in that an adhesive is narrowed between opposing electric terminal portions of the printed circuit board and the electric terminal portions are connected to each other. 2. The printed circuit board connection structure according to claim 1, wherein the conductor circuit of the electric terminal portion of at least one of the printed circuit boards has a convex shape on the side of the conductor circuit facing the conductor circuit. The conductor circuit of the electrical terminal portion of at least one of the printed circuit boards has a trapezoidal shape in which a side of the conductor circuit on which the cross section of the conductor circuit is opposed is shorter than a side on the insulating substrate side. 1 is a printed circuit board connection structure. The adhesive that is narrowed between the insulating material surface of the electrical terminal portion of one of the printed circuit boards and the insulating material surface of the electrical terminal portion of the other printed circuit board bonds the surfaces of both insulating substrates. The printed circuit board connection structure according to claim 1. The printed circuit board connection structure according to claim 1, wherein the adhesive is a thermoplastic or thermosetting resin. In the connection method of the printed circuit board including a plurality of conductor circuits formed on the insulating base material and having an electric terminal portion exposed to be electrically connected to another circuit board,
A printed circuit board characterized in that a sheet-like adhesive is narrowed between the other electrical terminal portions facing the one electrical terminal portion, and then the electrical terminal portions are joined by curing the adhesive. Connection method. 7. The printed circuit board connection according to claim 6, wherein a sheet-like adhesive narrowed between the electric terminal portions is molded so as to fit into a shape of a conductor circuit arranged in the electric terminal portion. Method.

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