JPH06326439A - Terminal structure and connecting method of printed wiring board - Google Patents

Abstract

PURPOSE:To obtain a terminal structure of a printed wiring board of high reliability where adjacent electrodes are prevented from deteriorating in insulating properties between them due to moisture absorption and connections are protected against breakage caused by a reduction in connection strength due to a decrease in connection pitch. CONSTITUTION:Electrodes 111a and through-holes 12a formed on a connecting surface 18a of a first printed wiring board 1a are surrounded with a peripheral pattern 13a. Electrodes and a peripheral pattern are formed on the connecting surface of a second printed wiring board 1b confronting and corresponding to the first printed wiring board 1a. The electrodes 111a and the peripheral pattern 13a formed on the connecting surface 18a of the first printed wiring board 1a and the electrodes and the peripheral pattern formed on the second printed wiring board 1b are made to overlap each other, and previously coated spare solder 2 is heated by a thermocompression bonding means or the like to connect the electrodes 11a and the peripheral pattern 13a together, and the electrodes 11a are completely enveloped with the peripheral pattern 13a and enhanced in connection reliability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal structure and a connecting method for electrically connecting printed wiring boards to each other.

[0002]

2. Description of the Related Art When soldering printed wiring boards directly to each other, the method shown in FIG. 6 is generally used. That is,
A plurality of electrodes 11a for electrical connection are provided on one surface (hereinafter referred to as a connection surface) 18a of the base material 17 of the first printed wiring board 1a.
An electrode group 111a composed of
a is a back side surface (hereinafter referred to as a back surface) through a through hole (not shown)
It is connected to the wiring pattern 19a. Although not shown, the connection surface 18b of the second printed wiring board 1b is not shown.
Electrode group 111a on connection surface 18a of first printed wiring board 1a
The electrode group having a shape and arrangement corresponding to,
Similarly to the printed wiring board 1a, each electrode is connected to the wiring pattern (not shown) on the back surface 19b through a through hole.

When connecting the printed wiring boards 1 having such a structure to each other, the electrode group of at least one of the printed wiring boards is coated with the preliminary solder 2 in an amount necessary for soldering in advance, and the first printing is performed. The electrode group 111a of the wiring board 1a and the electrode group of the second printed wiring board 1b are superposed, and the connecting portion is heated by means such as thermocompression bonding (heating direction: X) to connect the electrode groups.

[0004]

However, when soldering is performed as described above, the connected electrode group is exposed to the air, so that the base material between the electrodes and the flux residue between the electrodes are exposed under high temperature and high humidity. Is very easy to absorb moisture, and there is a problem that reliability is deteriorated due to deterioration of insulation between adjacent electrodes due to moisture absorption. Especially in recent years, since the connection pitch has become finer, the interval between adjacent electrodes has become very narrow,
The above problems are becoming more likely to occur. Also,
Since the area of the electrode itself is reduced due to the miniaturization of the connection pitch, the connection strength for each electrode is reduced, and the problem that the connection portion is easily broken due to external force or environmental change also arises.

The present invention solves the above problems,
An object of the present invention is to provide a terminal portion structure of a printed wiring board capable of obtaining a highly reliable connecting portion and a connecting method.

[0006]

In order to achieve the above object, a terminal structure of a printed wiring board according to the present invention has a terminal portion for connecting printed wiring boards to each other and electrically connects both printed wiring boards. A pattern of a shape surrounding the connection electrode group is provided on the outer periphery of the connection electrode group for, and the connection electrode group is connected to the signal line on the back surface of the printed wiring board through the through hole.

In the terminal structure of the printed wiring board according to the present invention, at least one through hole is provided in the base member inside the pattern surrounding the connection electrode group for electrical connection, and the through hole is formed after the soldering is completed. The hole may be closed.

In order to achieve the above object, the method of connecting terminals of a printed wiring board according to the present invention is to connect a printed wiring board having any of the above terminal structures by soldering in a vacuum atmosphere. .

In the printed wiring board terminal connecting method according to the present invention, the printed wiring board having any one of the above terminal structures can be soldered in a dry atmosphere.

[0010]

Embodiments of the present invention will be described with reference to the drawings.
It should be noted that in the following description, the parts common to the conventional ones will be denoted by the common reference numerals.

FIGS. 1A to 1D are views showing a first embodiment of a terminal portion structure of a printed wiring board according to the present invention. An electrode group 111a for electrical connection is formed on the connection surface 18a of the base material 17 of the first printed wiring board 1a.
1a is connected to the wiring pattern 14a on the back surface 19a through the through hole 12a, and is connected to the electrode group 111a and the through hole 1a.
A pattern (hereinafter referred to as an outer peripheral pattern) 13a that completely surrounds the 2a is formed around the 2a. Although the through hole 12a is formed within the range of the electrode 11a, it may be formed outside the range of the electrode 11a and connected to the electrode 11a by a wiring pattern as shown in FIG.

On the connection surface 18b of the second printed wiring board 11b, the electrode group 11 of the connection surface 18a of the first printed wiring board 1a is provided.
1a and the outer peripheral pattern 13a are opposed to each other, and the electrode group 111b and the outer peripheral pattern 13b having the corresponding shapes and arrangements are formed. Like the first printed wiring board 1a, each electrode 11b is provided on the back surface 19b through the through hole 12a. Wiring pattern 14
It is connected to b. Through hole 12b of first printed wiring board 1a and through hole 12b of second printed wiring board 2b
However, the through holes 12 may be arranged at positions not facing each other.

When connecting the printed wiring boards 1 having the above structure, first, the electrode group 111a and the outer peripheral pattern 13a of the first printed wiring board 1a and the electrode group 111b and the outer peripheral pattern of the second printed wiring board 1b. Overlap 13b. At this time, at least one of the electrode group 11 and the outer peripheral pattern 13 of the printed wiring board 1 is coated with the preliminary solder 2 in an amount necessary for soldering in advance. Next, the connecting portion is heated by means such as thermocompression bonding to connect the electrode group 11 and the outer peripheral pattern 13 to each other. At that time, the through hole 12 is also coated with the preliminary solder 2, and the solder 2 is filled so that the through hole 12 is completely closed.

When the connection is made by the above method, the electrode group 11 for electrical connection has the outer peripheral patterns 13a and 1a.
Since it is completely sealed by 3b, the inside of the outer peripheral patterns 13a, 13b, that is, the electrode groups 11a, 11b does not absorb moisture even in a high temperature and high humidity environment, so that the insulation is not deteriorated and the reliability is improved. Is improved. Also,
Since the connecting portions of the outer peripheral patterns 13a and 13b play a reinforcing role, stress is not applied to the electrode groups 11a and 11b even when an external force is applied, and the connection reliability is improved.

By the way, since the through holes 12a and 12b are exposed on the back surfaces 19a and 19b of both the printed wiring boards 1a and 1b, and the interval between the adjacent through holes 12a and 12b is wider than the interval between the electrodes 11a and 11b, the electrodes Group 11
Although reliability is improved more than when 1a and 111b are exposed, deterioration of insulation due to moisture absorption becomes a problem as the connection pitch becomes finer.

Therefore, as in the printed wiring board 1 of the second embodiment of the present invention shown in FIG. 3, when the through holes 12 are arranged in a zigzag pattern and the rear surface 19 has the wiring pattern 14, the pitch of the electrodes 11 does not change. Also, since the distance between the adjacent through holes 12 becomes wide, deterioration of the insulating property does not easily occur even if moisture is absorbed, and the reliability is improved. Of course, in FIG. 4, the through holes 12 are arranged in a zigzag in two stages, but a zigzag arrangement in three or more stages may be used.

Further, if the outer peripheral pattern is not connected to other patterns and is in an electrically floating state, noise is apt to occur and it becomes difficult to speed up the signal. Therefore, if the outer peripheral pattern 13 is connected to the power supply line 15 on the connection surface 18 and the outer peripheral pattern 13 is always stabilized at the power supply potential as in the third embodiment of the present invention shown in FIG. It is possible to speed up. In the present embodiment, the outer peripheral pattern 13 is connected to the power supply line, but even when connected to the ground line, the outer peripheral pattern 13 is stable at the ground potential, so that the same effect can be obtained.

When a flux containing a large amount of solvent component is used during soldering, the solvent component is volatilized when the electrode group is sealed with the outer peripheral pattern, and the internal pressure of the area sealed with the outer peripheral pattern increases. Stress may be applied to the connection part of the electrode, and the connection reliability may be reduced. Therefore, as in the fourth embodiment of the present invention shown in FIG. 5, an appropriate number of through holes 16 for degassing are provided within the range surrounded by the outer peripheral patterns 13a and 13b of the printed wiring board 1, and the solvent volatilized at the time of soldering. The component is allowed to escape from the through hole 16. Then, the internal pressure of the area sealed by the outer peripheral patterns 13a and 13b is not increased, and the connection reliability is improved. Furthermore, if the through holes 16 are closed with the adhesive 3 or the like after the completion of soldering, the periphery of the electrode group 111 does not absorb moisture even in a high temperature and high humidity environment, so that the insulation is not deteriorated and the reliability is improved. . It should be noted that the through hole 16 is not provided, the solvent component evaporated from the through hole 12 is removed, and after the connection is completed, the adhesive 3 or the solder 2
The through hole 12 may be closed by, for example, the like. The through holes 16 may be provided in at least one printed wiring board.

Further, when the atmosphere around the soldering portion is high in humidity, the high humidity air is also entrained in the area surrounded by the outer peripheral pattern 13 when the soldering is performed, so that the electrode group 111 is formed.
Since the surroundings absorb moisture, the insulation may deteriorate, resulting in a decrease in reliability. In order to solve this, a vacuum atmosphere is created around the attachment area when soldering. As a result, high-humidity air is not caught in the area surrounded by the outer peripheral pattern 13 and the periphery of the electrode portion 111 does not absorb moisture, so that the insulation is not deteriorated and the reliability is improved. The same applies when a dry atmosphere is provided around the soldering portion.

[0020]

As described above, the terminal structure of the printed wiring board according to the first aspect of the present invention has a pattern of a shape surrounding the outer periphery of the connection electrode group for electrical connection on both of the printed wiring boards to be connected. Since the connection electrode group is connected to the signal line on the back surface of the printed wiring board through the through hole,
The electrode group is completely sealed by the outer peripheral pattern, high temperature,
Even under high humidity conditions, the base material and the like around the electrodes do not absorb moisture, and the insulation reliability is improved. Also, because the outer peripheral pattern is connected,
Even if an external force is applied, the electrode group is not directly stressed,
There is also an effect that the connection reliability is improved.

A method of connecting a printed wiring board according to claim 3 is
When connecting the printed wiring board having the terminal structure according to claim 1 or 2, the soldering is performed in a vacuum atmosphere, so that the solvent component of the flux is not caught inside the outer peripheral pattern, and the connecting portion is prevented. Since stress is not applied to the connection, the connection reliability is improved.

A method of connecting a printed wiring board according to claim 4 is
When connecting the printed wiring board having the terminal structure according to claim 1 or 2, since the soldering is performed in a dry atmosphere, it is necessary to involve high humidity air in the outer peripheral pattern during the soldering work. In this case, the periphery of the electrode group does not absorb moisture, and the insulation reliability is improved.

[Brief description of drawings]

1A and 1B are views showing a first embodiment of a terminal portion structure of a printed wiring board according to the present invention, where FIG. 1A is a plan view of a connection surface, FIG. 1B is a plan view of a back surface, and FIG. ) Central section before connection,
(D) is a central sectional view after connection.

FIG. 2 shows an example in which a through hole is formed outside the electrode range.
It is a connection surface top view corresponded to (A).

3A and 3B are views showing a second embodiment of the present invention, in which FIG. 3A is a plan view of a connection surface and FIG. 3B is a plan view of a back surface.

FIG. 4 is a plan view of a connection surface showing a third embodiment of the present invention.

FIG. 5 is a sectional view showing a fourth embodiment of the present invention after connection, which corresponds to FIG. 1 (D).

FIG. 6 is a perspective view showing a conventional structure and method for directly soldering printed wiring boards to each other.

[Explanation of symbols]

 1a First printed wiring board 11a Electrode 111a Electrode group 12a Through hole 13a Outer peripheral pattern 18a Connection surface 19a Back surface 1b Second printed wiring board 11b Electrode 111b Electrode group 13b Outer peripheral pattern 14b Wiring pattern 18b Connection surface 19b Back surface 1 Printed wiring board 2 Spare solder 3 Adhesive 14 Wiring pattern 15 Power supply line 16 Through hole 17 Base material 18 Connection surface 19 Back surface

Claims (4)

[Claims] 1. In a terminal portion for connecting printed wiring boards to each other, a pattern of a shape surrounding the connecting electrode group is provided on the outer periphery of the connecting electrode group for electrical connection to both printed wiring boards. The terminal structure of the printed wiring board, wherein the connection electrode group is connected to the signal line on the back surface of the printed wiring board through the through hole. 2. The printed wiring board terminal structure according to claim 1, wherein at least one through hole is provided in the base material portion inside the pattern surrounding the connection electrode group for electrical connection, and soldering is performed. A terminal structure of a printed wiring board, characterized in that the through hole is closed after completion. 3. A method for connecting a printed wiring board having the terminal structure according to claim 1 or 2, wherein the soldering is performed in a vacuum atmosphere. 4. A method of connecting a printed wiring board having the terminal structure according to claim 1 or 2, wherein soldering is performed in a dry atmosphere.