JP2655447B2 - Multilayer printed wiring board for surface mounting and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed wiring board for surface mounting and a method of manufacturing the same, and more particularly, to a multilayer printed wiring board having surface mounting pads for mounting surface mounting components. The present invention relates to a wiring board and a method for manufacturing the same.

[Conventional technology]

Conventionally, the surface of a multilayer printed wiring board for mounting a surface mounting component (hereinafter referred to as a multilayer printed wiring board) is provided with surface mounting pads having a flat surface structure. The electrical connection between the component leads and the surface mounting pads of the printed wiring board has been performed via cream solder or the like. The method for manufacturing such a multilayer printed wiring board has no difference from the normal method for manufacturing a multilayer printed wiring board.

That is, in the case of a multilayer printed wiring board, a printed wiring board on which a circuit pattern is formed on one or both sides is heat-pressed through a plurality of prepregs to form a multilayer laminate, and after the through holes are formed, copper plating is applied to the entire surface. Then, a through hole is formed, and then a surface mounting pad is formed simultaneously with the surface circuit by a print-etching method.

[Problems to be solved by the invention]

Since the surface mounting pads of the conventional multilayer printed wiring board described above have a flat surface, the surface mounting of the surface mounted component leads and the multilayer printed wiring board can be compared to the method of soldering after inserting the component lead into a normal through hole. There is a disadvantage that the mechanical strength of the solder joint with the pad is not sufficient.

An object of the present invention is to provide a multilayer printed wiring board having high mechanical strength at a solder joint between a surface mounting component lead and a surface mounting pad.

[Means for solving the problem]

The surface mounting multilayer printed wiring board of the present invention has a surface mounting pad having a concave portion formed on the surface, and the side and bottom surfaces of the inner surface of the concave portion of the surface mounting pad are copper-plated. The diameter of the plane cross section circle of the recess of the pad is larger than the lead diameter of the surface mounting component to be mounted, and the bottom surface of the recess of the surface mounting pad is 3 mm from the surface conductor layer surface and the surface.
It is located on the same plane as the inner conductor layer surface located between the conductor layer surfaces of the layers.

The method for producing a multilayer printed wiring board for surface mounting according to the present invention includes the steps of: forming a through hole in a laminated board having copper foils on both sides, forming a through hole by performing copper plating on the entire surface including the inner wall of the through hole; Only forming a circuit by a normal printing-etching method, a step of applying a water-soluble or solvent-soluble resin to a surface on which the circuit is not formed and filling the through-hole with a resin, and the resin of the laminated plate The coated surface is arranged on the outside, and a laminated board having copper foil on both sides in advance is printed via a prepreg together with a double-sided printed wiring board and a single-sided printed wiring board having a conductor pattern formed on both sides or one side by a normal printing-etching method. A step of forming a multilayer laminate by thermocompression bonding, a step of dissolving and removing a resin adhering to the surface and the concave portions of the multilayer laminate, and providing a through hole in the multilayer laminate. After copper plating is performed on the entire surface including the inner wall of the through hole and the bottom surface of the concave portion, a surface mounting pad having a conductive circuit, a through hole and a concave portion is formed on the surface by a normal printing-etching method, and the through hole and the concave portion are formed. Applying a solder resist to portions other than the surface mounting pads.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

1 (a) and 1 (b) are a main part plan sectional view and a main part longitudinal sectional view for explaining the structure of a first embodiment of the present invention. Here, FIG. 1 (a) is a sectional view taken along the line BB 'of FIG. 1 (b), and FIG. 1 (b) is a sectional view taken along the line AA' of FIG. 1 (a).

As shown in FIGS. 1 (a) and 1 (b), the structure of the embodiment shown in FIG. 1 comprises a multilayer printed wiring board 30, an intermediate body 9, a conductive circuit 7 embedded inside, a conductive pattern 11, Hall 24,
It is composed of a conductive circuit 26, a surface mounting pad 27 and a solder resist 28 formed on the surface.
Has a concave portion 21 at the center, and has a structure in which the lead 41 of the mounted surface mount component 40 fits into the concave portion 21, and when soldering is performed by ring-shaped solder or solder paste, the solder is It is structured to be embedded in portions other than the leads 41.

2 (a) to 2 (m) are longitudinal sectional views of a main part shown in order of steps for explaining a method of manufacturing a multilayer printed wiring board according to the present invention.

First, a 0.1 mm thick glass fiber reinforced epoxy laminate 1 having 18 μm copper foil 2 as shown in FIG. 2 (a) bonded to both sides was prepared, and as shown in FIG. 2 (b) Drill a through hole 3 in the expected portion of pad 27, and
As shown in FIG. 3C, in order to make the entire surface including the inner wall of the through hole 3 conductive, a normal catalyst treatment and an electroless copper plating treatment are performed, and further, a copper plating 4 is formed by applying 20 μm of electrolytic copper plating. Thus, a through hole 5 was formed.

Next, as shown in FIG. 2 (d), an alkali-soluble photosensitive dry film etching resist 6 is laminated on both sides of the laminated plate 1, one surface is entirely exposed, and the other surface is masked. A predetermined circuit pattern was exposed and developed.

Next, as shown in FIG. 2 (e), the laminate 1 is spray-immersed in a copper chloride-hydrochloric acid-based etchant, and the copper foil 2 and the copper plating 4 other than the etching resist 6 are removed by etching. A conductive circuit 7 was formed on one side of the laminate 1 and immersed in an aqueous solution of caustic soda to dissolve and remove the etching resist 6.

Next, as shown in FIG. 2 (f), an alkali-soluble resin 8 was applied by a roller coater from the side opposite to the conductive circuit 7 forming surface of the laminate 1, and the solvent was volatilized at 120 ° C. to be solidified. . At this time, the viscosity of the resin 8 was adjusted so as to enter the inside of the through hole 5 and not to ooze out to the surface of the conductive circuit 7, and the resin 8 was applied and dried while a film was stuck on the conductive circuit 7 side to obtain an intermediate 9. .

Next, as shown in FIG. 2 (g), predetermined portions of the copper foil on both sides of the glass fiber reinforced epoxy resin laminated board having a thickness of 0.3 mm having a copper foil of 70 μm bonded on both sides are removed by etching. On both sides of a double-sided printed wiring board 10 having conductive patterns 11 formed on both sides, glass fiber impregnated with epoxy resin and semi-cured 0.1 mm thick prepregs 12 are arranged three by three. The surface of the obtained intermediate 9 on which the conductive circuit 7 was formed was placed on the inside, and a mirror plate made of stainless steel was further placed on the outside.

Next, as shown in FIG. 2 (h), the multilayer laminate 20 was spray-immersed in an aqueous solution of caustic soda to dissolve and remove the resin 8, thereby forming the concave portion 21.

Next, as shown in FIG. 2 (i), a predetermined portion where the through hole 24 is formed is drilled with a drill to provide a through hole 22.
As shown in FIG. 2 (j), the inner wall of the through hole 22 and the recess 21 are formed.
In order to make the entire surface of the multilayer laminate 20 including the bottom surface conductive, a catalytic treatment and an electroless copper plating treatment are performed, and then an electrolytic copper plating is performed by 30 μm to form a through hole 24 and a copper plating at the bottom of the concave portion 21. Was.

Next, as shown in FIG. 2 (k), an alkali-soluble photosensitive dry film etching resist 25 was laminated on both surfaces of the multilayer laminate 20, and a predetermined circuit pattern was exposed and developed using a mask. .

Next, as shown in FIG. 2 (l), the multilayer laminate 20 is spray-immersed in a copper chloride-hydrochloric acid type etching solution to remove the copper except for the etching resist 25 by etching. 26 and a surface mounting pad 27 are formed, and the etching resist 25 is dissolved and removed with an aqueous solution of caustic soda. As shown in FIG. 2 (m), a solder resist 28 is formed on the surface other than the through hole 24 and the surface mounting pad 27. This was applied to obtain a multilayer printed wiring board 30.

The lead of the surface mount component 40 in which the lead 41 shown in FIG. 1 is disposed on the lower surface of the multilayer printed wiring board thus obtained.
Attach a ring-shaped solder to 41 and attach the lead 41 to the surface mounting pad
27, and soldering was performed using a hot air oven. The portions of the surface mounting pad 27 other than the leads 41 of the recess 21 and the surface annular portion of the surface mounting pad 27 were completely filled with solder. Significantly higher solder joint strength was obtained compared to a normal flat surface mount pad without 21.

In the second embodiment, the structure of the surface mounting pad is exactly the same as that of the first embodiment, and a film-shaped alkali-soluble resin is used for forming the alkali-soluble resin 8 in the manufacturing method. The surface mounting pads 27 were formed in exactly the same manner as in the first embodiment except that the inside of the through hole 5 was buried by heating and pressing under reduced pressure on the side opposite to the formation of the multilayer printed wiring board.

The multilayer printed wiring board thus obtained also had the same solder joint strength as that of the first embodiment.

〔The invention's effect〕

As described above, the present invention has an effect of increasing the bonding strength of soldering by providing a structure in which a concave portion is provided in a surface mounting pad of a multilayer printed wiring board. Further, since the lead is fitted into the concave portion, there is also an effect that the position of the component does not shift during positioning of the component before soldering and during soldering.

The advantages of surface mounting are that components can be mounted from both sides, that the inside of the component mounting portion of the multilayer printed wiring board can be used as a wiring area, and that the vertical position of the component is accurately determined. There is almost no change in the multilayer printed wiring board.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are a main part plan sectional view and a main part longitudinal sectional view for explaining the structure of a first embodiment of the present invention, and FIGS. It is a longitudinal section of the important section shown in order of a process explaining a manufacturing method of a multilayer printed wiring board of the present invention. DESCRIPTION OF SYMBOLS 1 ... Laminated board, 2 ... Copper foil, 3 ... Through hole, 4 ... Copper plating, 5 ... Through hole, 6 ... Etching resist, 7 ... Conductive circuit, 8 ... Resin, 9 ... Intermediate, 10 ...
... double-sided printed wiring board, 11 ... conductive pattern, 12 ... prepreg, 13 ... insulator, 20 ... multilayer laminate, 21 ... recess, 22 ... through hole, 23 ... copper plating, 24 ... Through-hole, 25 ... Etching resist, 26 ... Conductive circuit, 27 ...
... Surface mount pads, 28 ... Solder resist, 30 ... Multilayer printed wiring board, 40 ... Surface mount components, 41 ... Leads.

Claims (2)

(57) [Claims] 1. A surface mounting pad having a concave portion formed on a surface thereof, wherein the side surface and the bottom surface of the inner surface of the concave portion of the surface mounting pad are copper-plated, and a plan sectional circle of the concave portion of the surface mounting pad is provided. Is larger than the lead diameter of the surface mounting component to be mounted, and the bottom surface of the concave portion of the surface mounting pad is located on the same plane as the surface conductor layer surface located between the surface conductor layer surface and the third conductor layer surface from the surface. A multilayer printed wiring board for surface mounting, comprising: 2. A through-hole is provided in a laminated board having copper foils on both sides, and copper plating is applied to the entire surface including the inner wall of the through-hole to form a through-hole. Then, a circuit is formed on one side only by a normal printing-etching method. Forming, applying a water-soluble or solvent-soluble resin to the surface on which the circuit is not formed, and filling the through-hole with the resin, and disposing the resin-coated surface of the laminate outside. A multi-layer laminate is prepared by heat-pressing a laminate having copper foil on both sides in advance and a double-sided printed wiring board having a conductive pattern formed on both sides or one side by a normal printing-etching method and a single-sided printed wiring board via a prepreg. And a step of dissolving and removing the resin adhering to the surface and the concave portion of the multilayer laminate, and providing a through hole in the multilayer laminate, and including the inner wall of the through hole and the bottom surface of the concave portion. Applying copper solder, and then applying a solder resist to portions except for surface mounting pads having conductive circuits, through holes and recesses on the surface by a normal printing-etching method. Of manufacturing a multilayer printed wiring board for surface mounting.