Molded plastic preform facilitates the fabrication of small lots of welded cordwood circuits. The preforms retain the components during welding and electrical checkout and facilitate encapsulation of the welded module when used with a conventional potting shell

Sturman, J. C.

English

NASA Technical Reports Server

Plastic Preform 
March 1968	 Brief 68-10063 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Plastic Preforms Facilitate Fabrication of Welded Cordwood Electronic Modules 
A reliable method has been developed to facilitate 
the fabrication of small lots (prototypes, experimental 
circuits, and other limited production quantities) of 
welded cordwood circuits. The essential feature of this 
method is the use of a molded plastic preform, or 
nesting jig, which retains the components during weld-
ing and electrical checkout. The preform also facili-
tates encapsulation of the welded module when used 
with a conventional potting shell. As the preform
and shell provide considerable structural support for 
the components, relatively soft resins can be used as 
encapsulants, thus permitting modifications or repairs 
to be readily made. 
Large holes in the preform are for transistors. Axial 
lead components fit in the smaller holes, which are 
molded with lands at one end to retain the compo-
nents during the welding operation. Although not a 
desirable operation, drilling out a few holes when 
(continued overleul) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
G.overnment assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19680000063 2020-03-12T05:44:19+00:00Z
necessary for slightly larger components eliminates 
the sloppy fits which would result if larger holes were 
originally molded in the preform. Drilled holes are 
also used for feedthrough of wires, since the holes 
are too small to be economically molded in the pre- 
form. Projections on the faces and sides of the pre- 
form allow it to be centered in the potting shell and 
ensure proper flow of encapsulant.
Note: 
Complete details can be obtained from: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B68-10063 
Patent status: 
No patent action is contemplated by NASA. 
Source: John C. Sturman. 
(LEW-90339) 
Brief 68-10063	 .	 Category 01


Plastic preforms facilitate fabrication of welded cordwood electronic modules

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