Cracking that causes pressure leakage in glass connector headers can be alleviated by manipulating the pin bridgewire connectors. This initiates the surface and meniscus cracks. Dry blasting the header surface with a fine abrasive then removes the cracks

Eckert, R. W.

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Bridg ass 
ader 
May 1967	 Brief 67-10148 
NASA TECH BRIEF	 G 
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. 
Cracks in Glass Electrical Connector Headers Removed
by Dry Blasting with Fine Abrasive 
The problem: 
Explosive cartridges that have two or four pin 
bridgewire connections, designed to mate with female 
connectors, contain a glass header which insulates 
the pins from the case. These connectors typically 
exhibit cracking of the glass around the pins. If left 
alone, these cracks can propagate through the glass
header causing a pressure leakage failure of the insu-
lator. Failure analyses have shown that most of these 
cracks, with few exceptions, are superficial and do 
not affect the integrity of the glass header. However, 
no satisfactory inspection criteria have been available 
to nondestructively distinguish between these and 
serious cracking. The only previous solution was to 
accept no cracks.
(continued overleaf) 
Now
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
Government 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=19670000148 2020-03-11T20:48:40+00:00Z
The solution: 
Manipulate each pin, following the fusing opera-
tion, to initiate the surface and meniscus cracks. Then 
dry blast the header surface with a fine abrasive, such 
as a household cleanser. 
How it's done: 
The major source of the cracking is the relatively 
minor flexing of the electrical pins after the header 
is fused. Slight pin movement, which occurs during 
operations such as cleaning, attachment of mating 
connectors for electrical tests, and installation • of 
shorting devices, easily chips and cracks the thin 
glass meniscus around the pin. The cracks produced 
in these areas propagate for various distances away 
from the pins through the relatively high stressed 
surface area. Surface cracking or spalling may also. 
occur independently of meniscus cracking due to the 
stress level on the surface. 
To remove the cracks, each pin is manipulated by 
hand with a cylindrical tool to initiate the surface and 
meniscus cracks. The header surface is. dry blasted 
with a fine abrasive to remove the thin weak areas of 
the meniscus cracks and the header surface which 
have been loosened by the pin manipulation. This. 
treatment results in a glass header which is free of 
superficial cracks, and no longer contains the highly 
stressed surface or weak meniscus areas.
Notes: 
I. Similar cracking of the header has been observed 
in cases where hard epoxies have been used as a 
header seal. Although no tests have been con-
ducted to date, a similar solution should be 
applicable. 
2. Inquiries concerning this innovation may be di-
rected to:
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B67-10148 
or to:
New Technology Representative 
General Dynamics/Convair Division 
Mail Zone 103-19 
5001 Kearny Villa Road 
San Diego, California 92112 
.Reference: B67-10148 
Patent status: 
No patent . action is cbntemplated by NASA. 
Source: R. W. Eckert

of General Dynamics/Convair Division

under contract to

Lewis Research Center

(Lewis-381) 
Brief 67710148	 Category 03


Cracks in glass electrical connector headers removed by dry blasting with fine abrasive

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