[BC] Soldering D-sub Pins

[Gregory Muir]

Crimp style contacts have been used on aerospace equipment for as long as I 
can remember.  During my stint in the Air Force in the late 60's we were 
using crimped contacts at that time in our fighter aircraft.  This included 
the F-105 and A7 birds.  Of course, there was also the assortment of 
soldered types too depending on who manufactured the assemblies.  Regarding 
the current consensus of crimped contacts on aircraft the FAA states in 
their requirements that connectors using crimped contacts are generally 
chosen for ease of assembly and maintenance.  And they can be used for all 
applications except those requiring a hermetic seal which then requires 
soldered connections.  You can read more in FAA FAR 25.1529.  And, of 
course, this does not address the thousands of soldered joints in various 
electronics assemblies that populate today's aircraft.

SAE International, which sets standards for both automotive and aerospace 
hardware (including aircraft) also publishes several standards for soldered 
connections.  Of note is the current SAE AS4461, "Assembly and Soldering 
Criteria for High Quality/High Reliability Soldered Wire and Cable 
Termination in Aerospace Vehicles."

During the 1980's I was involved in space satellite design with the 
government.  Our reliability for both soldered and crimped connections was 
assured by workmanship standards such as the one you had mentioned 
(NASA-STD-8739-4).  Each assembly worker had to complete a one-week course 
on both solder and crimp skills before they could become certified for 
assembly tasks.  Then each completed end item was inspected and certified 
prior to submission for either final assembly or spares storage.  The main 
determining factor regarding selection between crimped or soldered 
connections was that of the environment the connections would be working in. 
Since soldering was prone to outgassing in a space vacuum environment and 
many of my designs incorporated precision optical components which were very 
cold and subject to gaseous material condensation, I often opted for crimped 
contacts.  Of course, the wire insulation was also critical and Teflon was 
the material of choice but not entirely "clean" for the application.

As for the solderless crimp termination, it has been commonly known that AMP 
was the frontrunner in this technique since the early 1940's.  Obviously 
many other manufacturers quickly jumped on the bandwagon in the early stages 
to copy their approach.  It is interesting to note that during the 1960's 
AMP encountered some difficulty in obtaining aerospace approvals on some of 
their crimp products while a few other manufacturers had improved upon the 
process and went ahead and won acceptance.  It wasn't very long before AMP 
caught up and again secured the market.

Greg Muir



----- Original Message ----- 
From: <RichardBJohnson at comcast.net>
To: "Broadcasters' Mailing List" <broadcast at radiolists.net>
Sent: Friday, April 11, 2008 9:44 AM
Subject: Re: [BC] Soldering D-sub Pins


>
> Well...."the rest of the story...." It used to be that every electrical
> connection in aircraft was REQUIRED to be soldered. As aircraft
> aged, the soldered connections failed and circuits opened up [2].


<snip>

> Cheers,
> Richard B. Johnson