JPH08236896A - Printed board device - Google Patents

Abstract

PURPOSE: To eliminate the additional application of sheet to a printed board device, which is provided by mounting electronic components on a printed board. CONSTITUTION: A printed board 16 is provided with a through hole 15, the diameter of the through hole 15 on the printed board rear side 19 is smaller than that on the printed board front side 18. During the reflow process, since the the hole diameter on the printed board front side is large, metal particles of cream solder 17 are prevented from being sucked up to the printed board front side 18 on the printed board top face, even with the capillary phenomenon of the cream solder 17, because the a space between the hole 15 of the printed board 16 and a lead terminal 6 is small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board device in which electronic parts are mounted on a printed circuit board.

[0002]

2. Description of the Related Art A conventional printed circuit board device will be described below.

In a conventional printed circuit board device, as shown in FIG. 3, an electronic component 3 is mounted on a printed circuit board 2 having a through hole 1. The electronic component 3 had the element 4 inside the metal case 5. The element 4 has a lead terminal 6 that is electrically connected, and the lead terminal 6 is led out from the metal case 5 and inserted into the hole 1 of the printed board 2. On the printed circuit board 2, the cream solder 7 is applied to the back surface 9 of the printed circuit board in advance (the application state of the cream solder is not shown), and the electronic component 3 is mounted on the printed circuit board 2 and then reflow soldering is performed.

[0004]

However, in such a conventional structure, part of the cream solder 7 travels through the gap between the hole 1 of the printed board 2 and the lead terminal 6 and rises in the hole 1 during reflow. It was considered that the end portion 10 of the metal case 5 and the lead terminal 6 were short-circuited by the cream solder 7a. The reason for this is that the cream solder 7 is a mixture of metal particles and liquid flux, and during reflow, the liquid flux is sucked up in the holes 1 of the printed circuit board 2 by a capillary phenomenon and at the same time lifts the metal particles.
Further, a boundary surface 11 between the metal case 5 of the electronic component 3 and the substrate 2
The cream solder 7 spreads over the end 10 of the metal case 5.
It was considered that the lead terminal 6 was short-circuited by the cream solder 7a. In order to prevent this, as shown in FIG. 4, an insulating sheet 12 is inserted between the metal case 5 of the electronic component 3 and the boundary surface 11 between the printed circuit boards 2 and soldered. As shown in FIG. 5, the sheet 12 has the lead terminals 6 so that the lead terminals 6 of the electronic component 3 can be inserted.
Holes 13 having substantially the same interval as are provided. Since the hole 13 has substantially the same hole diameter as the lead terminal 6, even if the cream solder 7 moves up through the gap between the hole 1 of the printed board and the lead terminal 6, the lower surface 1 of the sheet 12 is
It is cut off at 4 and the cream solder 7 does not rise any further. Therefore, the cream solder 7a does not short-circuit between the end 10 of the metal case 5 and the lead terminal 6. However, the method of inserting the sheet 12 requires the sheet 12, and there is a problem that it takes time and effort to insert the lead terminal 6 of the electronic component 3.

The present invention solves such problems, and an object of the present invention is to provide a printed circuit board device which does not require insertion of a sheet.

[0006]

In order to achieve this object, the through hole of the printed circuit board device of the present invention has a smaller hole diameter on the back side of the printed circuit board than on the front side of the printed circuit board on which electronic components are mounted. In addition, the hole diameter on the back surface side of the printed circuit board is made substantially equal to the lead terminal diameter.

[0007]

With this structure, the through hole of the printed circuit board into which the lead terminal of the electronic component is inserted has a small hole diameter on the back surface of the board (hole diameter of the cream solder application surface), so that even if reflow occurs, there is a capillary phenomenon of cream solder. However, since the gap between the through hole of the printed circuit board and the lead terminal is narrow, the metal particles of the cream solder cannot be sucked up onto the surface of the printed circuit board. Even if sucked up, since the through hole of the printed board is widened on the electronic component device side, the gap between the through hole of the printed board and the lead terminal is widened and the capillary phenomenon is eliminated. Therefore, since the metal particles of the cream solder do not suck up, the metal case end of the electronic component and the lead terminal are not short-circuited. Therefore, it is not necessary to add a sheet to the boundary surface between the electronic component and the printed circuit board.

[0008]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a printed circuit board device according to an embodiment of the present invention. In FIG. 1, the electronic component 3 is mounted on a printed board 16 having a through hole 15. The electronic component 3 has an element 4 inside a metal case 5. A lead terminal 6 electrically and mechanically connected to the element 4.
The lead terminal 6 is led out from the metal case 5 and inserted into the hole 15 of the printed circuit board 16. On the printed board 16, the cream solder 17 is applied in advance to the soldering lands 20 on the back surface 19 of the printed board (the application state of the cream solder is not shown), and the lead terminals 6 of the electronic component 3 are inserted into the through holes of the board 16. After being inserted in 15, reflow soldering is performed to connect the lead terminals 6 of the electronic component 3 and the soldering lands 20 of the printed board 16 by soldering.

FIG. 2 is a partially enlarged sectional view showing a soldered state of the through hole 15 of the printed board 16 and the lead terminal 6 in FIG. The through hole 15 of the printed circuit board 16 into which the lead terminal 6 of the electronic component 3 is inserted has a hole diameter B on the printed circuit board rear surface 19 side smaller than a hole diameter A on the printed circuit board front surface 18 side on which the electronic component 3 is mounted, and B
The dimensions are substantially equal to the diameter of the lead terminal 6. The B dimension is about 1.5 to 2.0 times, preferably about 1.5 times the diameter of the lead terminal 6. That is, the through hole 1
5 is important for the relationship of A> B, and the printed circuit board surface 1
The hole diameter on the 8 side is expanded. That is, it has a taper that spreads from the back surface of the printed circuit board toward the front surface. This also serves to improve the insertability of the lead terminal 6.

[0011]

As described above, according to the present invention, the through hole of the printed board is made smaller in diameter on the back side of the printed board than on the front side of the printed board, and the hole diameter on the front side of the printed board is expanded. Therefore, even if there is a capillary phenomenon of the cream solder during reflow, the gap between the hole of the printed board and the lead terminal is narrow, so that the metal particles of the cream solder cannot be sucked up to the upper surface of the printed board. Even if sucked up, the through hole of the printed circuit board is widened on the front surface side of the printed circuit board, so that the gap between the hole of the printed circuit board and the lead terminal is widened and the capillary phenomenon is eliminated. Therefore, since the metal particles of the cream solder do not suck up, the metal case end of the electronic component and the lead terminal are not short-circuited. Therefore, it is not necessary to add a sheet to the boundary surface between the electronic component and the printed circuit board.

Further, if the hole diameter on the surface side of the printed board is tapered, the workability of inserting the lead terminal into the through hole of the printed board is improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a printed circuit board device according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of the main part of FIG.

FIG. 3 is a sectional view of a conventional printed circuit board device.

FIG. 4 is a cross-sectional view showing a state in which a sheet is inserted into a boundary surface between a metal case and a board of a conventional electronic component.

FIG. 5 is a perspective view of a conventional seat.

[Explanation of symbols]

 3 Electronic Components 4 Element 6 Lead Terminal 15 Through Hole 16 Printed Circuit Board 18 Printed Circuit Board Front Side 19 Printed Circuit Board Back Side

Front page continuation (72) Inventor Nobuyoshi Kozuka 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A printed circuit board having a through hole, and lead terminals mounted on the upper surface of the printed circuit board and connected to elements housed inside a metal case are mounted on the printed circuit board through the through hole. A printed circuit board having an electronic component, wherein the through hole has a hole diameter smaller on the printed circuit board rear surface side than the printed circuit board front surface side on which the electronic component is mounted, and the hole diameter on the printed circuit board rear surface side is substantially equal to the lead terminal diameter. apparatus. 2. The through hole has a taper extending from the back surface of the printed board toward the front surface of the printed board.
The printed circuit board device described.