Solder paste stenciling apparatus and method of use for rework

(12) United States Patent

Mayer

US006253675B1

(io) Patent No.: US 6,253,675 Bl (45) Date of Patent: Jul. 3,2001

(54) SOLDER PASTE STENCILING APPARATUS AND METHOD OF USE FOR REWORK

(76) Inventor: Carl P. Mayer, 43 Pleasant St., Sharon, MA (US) 02067

( * ) Notice: Subject to any disclaimer, the term ol this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.

(21) Appl. No.: 09/342,839

(22) Filed: Jun. 29, 1999

(51) Int. C I. B05C 17/06

(52) U.S. CI 101/127.1; 101/128.21;

101/129

(58) Field of Search 101/114, 127,

101/127.1, 128.21, 128.4, 126, 129

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"Surface Mount Micro-Screener," IBM Technical Disclosure Bulletin, 37 (11) :271-274 (Nov. 1994). Chai, Y. S., "Solder Paste Printing for BGA Rework," Circuits Assembly, pp. 30-31 (Oct. 1997). Hwang, J.S., "BGA Rework Considerations," SMT, pp. 18-19 (Nov. 1998).

Gislao, M.J., "Reworking CSPs," SMT, pp. 63-64 (May 1998).

Goulker, B. R., "Selecting a Metal Stencil," Electronic Packaging & Production, pp. 35, 36, 38, 40, 41 (Oct. 1998). Zamborsky, E., "Fundamentals of BGA Rework," SMT, pp. 76, 78, 79 (Feb. 1999).

Russell, E., "Preparing the Site," PCBAssembly, pp. 20-22, 24 (Feb. 1999).

Miller, G. and Zweig, S., "BGARework and X-Ray Inspection," SMT, pp. 62-64 (Apr. 1999).

Primary Examiner—Ren Yan

(74) Attorney, Agent, or Firm—Hamilton, Brook, Smith & Reynolds, PC.

(57) ABSTRACT

A solder paste stencil printing apparatus and method for applying a controlled pattern and volume of solder paste onto a single area array component site on a populated printed circuit board (PCB). The stencil is a disposable, adhesive-backed, flexible, polymer membrane. The stencil has a plurality of holes in a pattern corresponding to a component site pad pattern on a printed circuit board. A periphery area of the stencil can be folded or shaped to fit into the available space to be stenciled. The method of applying the solder paste to the PCB includes shaping the stencil to fit available space, removing protective adhesive backer layer, aligning stencil with mating pad pattern on the PCB, and adhering stencil to PCB surface. The secure stencil insures efficient, accurate alignment and secure gasketing of stencil apertures to PCB pad pattern. Solder paste is then dispensed onto stencil surface, squeegeed across stencil surface until all apertures are filled level with top surface. Removable adhesive-backed stencil is then peeled away from the PCB surface to reveal finished solder paste pattern. The used stencil is disposed.

21 Claims, 8 Drawing Sheets

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