HOW MANY WRAPS BEFORE SOLDERING?

October 4, 1957 was a day of well earned celebration in the Soviet Union for it was on that day they beat the United States in launching the first artificial satellite which they called “Спутник” (Sputnik) meaning “co-traveler”, “traveling companion” or “satellite”. This was the beginning of the “Space Race” which diverted some of the tension caused by the “Cold War.”

The United States was not able to successfully launch an artificial satellite until April 28, 1958. Prior to that successful launch the US had blown up two rockets on the launch pad. After that success they blew up four more rockets before finally again succeeding.

NASA, which came into existence in 1958, found the reason for the failure was do to not bad engineering but was the result of poor quality control especially in the area of soldering. NASA developed some changes in soldering technique. These changes not only virtually eliminated solder connection failure but also reduced the weight of the vehicle and payload.

Prior to the new standards of soldering a wire being soldered to a terminal was wrapped at least a full 365 degrees and most of the times two or three times then it was soldered. NASA standards said a wrap was to be no more then 90 degrees.

Another change NASA instituted was the way a PC board was loaded. Up to that time when a component was placed in a PC board the leads were bent and run through the board then bent again to run along the trace then it was trimmed and soldered. The new NASA standards called for the leads to be bent at least the diameter of the lead away from the component, inserted into the lead holes with the leads sticking straight out, and then the leads were cut almost flush with the board trace and soldered.

The main complaint with the NASA standards of soldering was if a solder connection was missed that component could fall out, a wire could fall off the connector, or it would fail when tested especially if vibrated during test. The funny thing about that argument is it is exactly right and that is why it makes it the best way to do the job. Using the old standards a missed solder connection may test well when first made but it is a failure waiting to happen as the contact ages. If a component falls out or if the wire drops off the connection so it is easy to see before testing repair can be made at that time. If the unit is vibrated during testing so missed solder connections will fail at that point it will prevent failure later during more critical operating conditions.

When constructing a project carefully clean the surface of each solder joint with a pencil eraser. A little rosin flux can be added to the surfaces to be soldered to prevent oxidation and help conduct heat. Use sufficient heat to melt the solder quickly and melt the solder on the contact surfaces and not on the soldering iron. Use very little solder. Clean flux residue with denatured alcohol using an acid brush while the it is still hot but the solder is solid.

By following these few soldering tips your completed project should give you many years of failure free service. Another added advantage is defective components can be removed with little effort so they can be replaced.

I was taught these standards while working as a technician for the US Army at the Sacramento Army Depot in 1968.  A lot has changed sense those days but I still apply these standards on all my projects. And by applying them while working in the commercial two way radio industry my solder connections did not fail.  Oh I had people tell me I was not doing it right but they still did not fail.

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4 Responses to HOW MANY WRAPS BEFORE SOLDERING?

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