US 6,785,960 B2 · Wave solder application for ball grid array modules

Abstract

A method for fabricating a printed circuit board assembly comprising a via, wherein the method inhibits the flow of molten solder into the via during a wave soldering step, thereby preventing heat transfer that might otherwise degrade a solder joint at a top pad that is thermally coupled to the via. The method comprises the steps of: (1) fastening a bottom component to the bottom surface of the circuit board by a screening and reflow of solder paste that also generates a solder plug in the via; (2) fastening top components to the top surface of the circuit board by a screening and reflow of solder paste, wherein the top components comprise ball grid arrays and other surface mount devices that are to be affixed to pads which are connected to vias; and (3) wave soldering the bottom surface to affix additional components onto the circuit board, such as pin-in-hole components placed on the top surface. The solder plug formed in the via during the first step prevents molten solder from flowing into the via during the subsequent wave soldering step, thereby inhibiting heat transfer from the molten solder to the solder joint at the top pad.

Claims17

Dependent claims

A method for constructing a printed circuit board assembly, comprising the steps of:

(a) providing a printed circuit board comprising:
a top surface comprising a top pad, wherein the top pad is electrically connectable to a top component;
a bottom surface;
and
a via extending through the circuit board from the top surface to the bottom surface, wherein the via is electrically connected to the top pad, and wherein the via includes an opening at the bottom surface;
(b) forming a plug in the via by inserting a volume of material into the via through the opening in the via;
and
(c) contacting an end of the plug with molten solder, wherein the end of the plug is at the bottom surface, and wherein the plug obstructs flow of the molten solder into the via.

5 more elements

A method for constructing a printed circuit board assembly, comprising the steps of:

(a) providing a printed circuit board comprising:
a top surface comprising a top pad, wherein the top pad is electrically connectable to a top component;
a bottom surface;
a middle layer between the top surface and the bottom surface comprising an electrical circuit pattern;
and
a via extending through the circuit board from the top surface to the bottom surface, wherein the via is electrically connected to the top pad, wherein the via is electrically connected to the electrical circuit pattern, and wherein the via includes an opening at the bottom surface;
and
(b) plugging the via while installing a bottom component onto the bottom surface, by a process comprising the steps of:
screening solder paste, wherein the screening inserts solder paste into the opening in the via to form a solder mass within the via and onto a bottom pad located on the bottom surface to form a solder layer;
placing the bottom component on the bottom surface, wherein the bottom component is in mechanical and electrical contact with the solder layer;
and
reflowing the solder mass and the solder layer, wherein the solder mass is redistributed within the via so as to form a plug in the via, and wherein the bottom component is mechanically and electrically affixed to the bottom surface;
and
(c) installing the top component on the top surface, wherein a contact element of the top component is mechanically and electrically affixed to the top pad.

11 more elements

Dependencies are inferred from the claim text.

Wave solder application for ball grid array modules

Life of this patent

Wave solder application for ball grid array modules

Life of this patent

Abstract

Claims17