JPH0821764B2 - Printed board - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a double-sided or multi-layered printed board on which a surface mounting element (hereinafter abbreviated as SMD) is mounted and used.

[Prior Art] The connection of the patterns on the front and back surfaces of a double-sided printed circuit board and the connection of the patterns between the layers of a multilayer printed circuit board are usually performed by partially removing the insulating layer and plating the inside with a copper or the like. This is done by providing through holes.

Also, for example, solder an SMD such as a chip component or flat package type IC on the land on the front side of the printed circuit board,
When connecting the terminals of the SMD to the circuit pattern on the back side or another layer, a through hole is provided at a position slightly apart from the land to make the connection.

[Problems to be Solved by the Invention] As described above, providing the through hole at a position apart from the SMD land has been a hindrance to higher integration of the printed circuit board and improvement of the component mounting density. .

Hereinafter, the reason why the conventional through hole has to be provided at a position apart from the SMD will be described.

As a method of soldering SMD on the land of the printed circuit board, a so-called reflow soldering method is usually used, in which cream solder is applied on the land for SMD in advance by a printing method, etc. It is used. For example, when SMD soldering is performed by the reflow soldering method on a printed circuit board with through holes in the SMD land, during the process of melting cream solder,
The melted cream solder flows into the through holes. As a result, the amount of cream solder to be soldered between the SMD and the land is insufficient, and stable soldering cannot be performed. In addition, the cream solder that has flowed into the through holes may flow out to the pattern on the back surface, which may adversely affect the pattern.Furthermore, near the through holes on the back surface, the heat of the melted cream solder may affect the pattern. This imposes a restriction on component mounting, which means that it is not possible to mount components that require

On the other hand, in order to prevent the inflow of the cream solder into the above-mentioned through hole, if the through hole is previously closed with a filling material such as epoxy resin and reflow soldering is performed, the space between the filling material and the SMD is reduced. Another problem is that the air in the gap created by the heat expands due to heat and the pressure causes the SMD soldering position to shift. When solder is used as the filling material for the purpose of preventing the occurrence of the gap as described above, the molten filling material as described above flows out to the pattern on the back surface and adversely affects the pattern. For this reason, the tendency that component mounting is restricted near the through hole on the back surface becomes remarkable.

For the reasons described above, the conventional through hole is provided at a position slightly away from the SMD land.
High integration of double-sided or multi-layer printed circuit board,
This has been an obstacle to improving the component mounting density.

The present invention has been made in view of the above problems, and its object is to provide through holes used for connecting patterns between front and back or multiple layers at positions of lands for SMD,
Therefore, an object of the present invention is to provide a double-sided or multi-layered printed circuit board in which the area of the wiring pattern portion is small, the component mounting density is high, and at the same time, good soldering can be stably performed.

[Means for Solving the Problems] The above object of the present invention is to solder the surface mount element in a land for soldering a connection terminal of a surface mount element that requires connection through a through hole. It is achieved by a printed circuit board characterized in that a through hole whose inner side is closed and a through hole whose inside is filled with solder is provided.

The position of the through hole of the present invention is preferably a position within the SMD land in consideration of high integration, but the through hole is partially exposed outside the SMD land, for example. Is also effective.

The covering material of the present invention may be any one as long as it can block the solder filling the inside of the through hole so as not to flow out, but the necessary and unnecessary parts of the covering are selectively covered. It is preferable to use a film resist because it can be easily performed by performing the steps of exposure and development, and sufficient strength can be obtained.

Next, a specific example of the method for manufacturing a printed circuit board of the present invention will be described below, but the present invention is not limited to this.

First, a conventional method, ie, drilling of a base material, copper plating in a through hole, formation of an etching mask, and etching are performed to form a pattern including a through hole and a land. Next, a film resist is laminated on both sides, only a necessary portion is exposed and developed, and the resist is coated only on a portion where soldering is not desired. At this time, the non-mounting side entrance of the through hole located in the land is closed with a resist. Next, when a solder leveler process is performed, the inside of the through hole located in the land is filled with solder. When the SMD is soldered to the double-sided printed circuit board manufactured in this way by the reflow soldering method described above,
A double-sided printed wiring board can be obtained. The above is an example of a double-sided printed circuit board, but if a multilayer printed circuit board which is internally formed in advance is used as the circuit board, the multilayer printed circuit board of the present invention can be manufactured in the same manner as the above method.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a partial perspective view showing an embodiment in which an SMD is mounted on a printed board of the present invention. A wiring pattern 104 and SMD lands 103a and 103b are provided on the substrate 1, and SMD2 is soldered to the SMD lands 103a and 103b.

FIG. 2 is a partial sectional view showing an embodiment of the printed circuit board of the present invention. Wiring patterns 104 and 204 and film resists 105 and 205 are formed on the front side and the back side of the substrate 1, respectively, and the wiring pattern 104 on the front side and the pattern 204 on the back side are connected by through holes 8 and 9.

Further, SMD lands 103a and 103b are provided on the front side of the substrate 1. Further, the through hole 8 for connecting the SMD land 103a and the wiring pattern 204 on the back side is located immediately below the SMD land 103a, the inside thereof is filled with the solder 6, and the back side entrance is a film resist 205. It is blocked. Incidentally, the through hole 9 which is not related to the connection of the SMD terminal has a hollow inside as usual, and is not blocked by the film resist 20 either.

FIG. 3 is a partial sectional view showing an embodiment in which the SMD is mounted on the printed board of the present invention. The cream solder 7 is formed on the SMD land 103a of the printed circuit board of the present invention shown in FIG. 2, and the SMD 2 is soldered thereon in a good condition.

4 and 5 are views showing a conventional printed circuit board.

In the printed circuit board shown in FIG. 4, the through hole 8 is provided at a position apart from the SMD land 103a. Therefore, the wiring pattern 104 circulates to the outside, which is inferior to the printed circuit board of the present invention shown in FIG. 1 in terms of compactness.

In the printed circuit board shown in FIG. 5, the through hole 8 is provided immediately below the SMD land 103a, but the inside of the through hole 8 is kept hollow and the back surface is not covered with the film resist 205, and the through hole 8 is formed on the SMD land 103a. This is a printed circuit board after cream solder 7 is formed on and SMD2 is soldered on it.
The cream solder 7 flows into the through hole 8 due to the heat when soldering the SMD2, and the SMD2 and the land 103a.
Is not soldered sufficiently.

[Effects of the Invention] As described above, the printed circuit board of the present invention is
Since the through hole for connecting the terminal of the SMD mounted on the land on the front side and the wiring pattern on the back side is provided in the land, the area of the wiring pattern portion can be reduced and the component mounting density can be increased. Furthermore, the SMD can be stably soldered on the land.

[Brief description of drawings]

1 to 3 are views showing an embodiment of a printed circuit board of the present invention, and FIGS. 4 and 5 are views showing a conventional printed circuit board. 1 ... Substrate, 2 ... SMD, 103a, 103b ... SMD land, 104, 204 ... Wiring pattern, 105, 205 ... Film resist, 6 ... Solder, 7 ... Cream solder, 8, 9 ... … Through holes.

Claims (1)

[Claims] 1. A land for soldering a connection terminal of a surface-mounting element which requires connection by a through hole is closed at an inlet opposite to a side to which the surface-mounting element is soldered. A printed circuit board having a through hole whose inside is filled with solder.