David A Walcott

US Patent:

52941990, Mar 15, 1994

Filed:

Oct 29, 1992

Appl. No.:

7/968547

Inventors:

Harry D. Boersen - Holland MI
John M. Eldred - Holland MI
Robert K. Hayes - Fruitport MI
Vince J. Jasinski - Grand Rapids MI
Kim A. Pattee - Holland MI
Clinton A. Peterson - Holland MI
David L. Walcott - Zeeland MI

Assignee:

Venturedyne, Ltd. - Milwaukee WI

International Classification:

G01N 360

US Classification:

374 57

Abstract:

The invention is an improvement in a thermal stress screening system of the type using a single type of liquid for alternately transferring heat to and from the product. In the improvement, the product is confined in a single chamber during alternate heat transfer. That is, the system provides "one chamber" thermal stress screening. The system includes a plurality of tanks, one each for hot and cold liquid, and a heat exchanger associated with each tank so that the liquid in a tank is maintained at the proper temperature for stress screening. An improved method for thermally stress screening products, e. g. , printed circuit boards, includes the steps of placing the product in a chamber, flowing cold liquid into the chamber, draining the cold liquid from the chamber and flowing hot liquid into the same chamber.