Solid mechanical connection before solder is applied?

[W3SLK]

I remember the 2M NASA standards. What a drag in the bag. No coffee, no cigarettes and some guy looking over your shoulder. I had to remediate at least 2 times before I passed. I still think I did my better soldering being high on coffee and my eyes dripping tears as a result of the smoke from the cigarette hanging from my mouth! They used to take our solder joints and run them under a microscope to see if we used the proper amount of heat and no cold joints existed. What a pain!

[k4kyv]

All the soldering precautions in the world won't prevent failures caused by the notorious "tin whiskers" that grow on connections made with EU-mandated lead-free solder.

[N3DRB The Derb]

The Keller Weller KESTER stuff circulating through the hamfest circuit last year by the rollfulls has proven to be damn good solder - I hope I see more at Richmond because I'm gonna buy 9 rolls worth if it's still 3 bucks a roll. need the 2 other sizes. It fluxes great and wets like a new puppy on yer floor. What time brings, I dunno, but it works.

[W3RSW]

All the soldering precautions in the world won't prevent failures caused by the notorious "tin whiskers" that grow on connections made with EU-mandated lead-free solder.

Boy, your right on that one Don.
If the electronic world thinks the current, draconian lithium battery fires are spontaneous, wait 'till consumer and military circuits start imploding in increasingly random flakes all over the place from those solder shorts.

Unintended consequences ought to be high on the syllabus of 'green courses' everywhere.

Political science now has a new meaning. Ask Al.

[K3ZS]

Can you buy lead-tin solder at retail outlets now in the U.S.?  If not, I will have to go to a hamfest and stock up also.

[W1RKW]

Can you buy lead-tin solder at retail outlets now in the U.S.?  If not, I will have to go to a hamfest and stock up also.

A couple of years ago I went on a solder buying binge when word of banning tin/lead solder was in the news.  Got around 40 rolls of various types and sizes.

[WQ9E]

Can you buy lead-tin solder at retail outlets now in the U.S.?  If not, I will have to go to a hamfest and stock up also.

Still available from Mouser and others but probably not too many more years.  I stocked up last year.

Even if it disappears it will be available at hamfests for years I am sure.  But I prefer to buy the basics from stores and use my hamfest time stalking items which truly are difficult to find.

[K9PNP]

If whomever had my Viking II before me had made good mechanical connections before soldering, I would probably have less time invested troubleshooting after doing the initial rebuild.  Little things like cold solder joint on HV rectifier tube socket; made a nice arcing sound when it pulled apart a little.  And, on the other end of the spectrum, the big globs of solder on certain terminal strips like the one holding the modulation transformer secondary wires.  The globs were so close, I'm lucky the air was relatively dry.  Yeh, I hate to take good connections apart later, but I still believe in the old military version of connections.  Even mine are good for only so many G's.

[WQ9E]

I have to dig out the article I cited earlier but one of the reasons listed for not doing mechanically solid was that it could hide a cold solder joint. 

[K5UJ]

Last time I checked about two months ago I could get leaded solder at home depot.  In the tool dept. near where they have the welding equipment.  Solder has gotten expensive.

[Jim KF2SY]

I think the answer to original post would be
"sometimes" and/or "it depends"  if the item resides in our real world of a non-vibrating cozy hamshack,
then wrap or don't wrap accordingly.  Also, I would think stranded is easier on delicate switches and
such than solid with stiff teflon coating.  The stresses,application (current), and environment should be taken into account on a case by case basis. 

Here is a link to the ol' MIL 2000A standard circa 1995.  No superceding document, but I beleive IPC
standrds are the industry baseline now.  Enjoy -- and don't read this while driving or operating heavy machinery.  Recommended for occasional insomnia.

https://assist.daps.dla.mil/docimages/A/0000/0006/7966/000000148792_000000139462_DDOMCHAMQJ.PDF?CFID=4334763&CFTOKEN=10774777&jsessionid=5c3017abef78c8470af0667c357e23c5e736

 

[W3SLK]

Now, let me throw a monkey wrench in all this. Having stated that I attended the US Navy's version of NASA Micro/Miniature Soldering School and learned to solder on joints that were mechanically sound, a lot of the equipment I did work on, especially the computers and other peripherals in the data chain were 'wire wrapped' onto the terminals. Typically these were at the card slots or on mother board/buss-es where a square pin extended out the back and a 'wrapping gun', (not to be confused with Eminem's gun), was used to put roughly 6~8 turns of wire on the pins. I was stationed aboard an aircraft carrier where every time they would launch a plane, you would feel the jolt of the catapult piston throughout the ship. Say what you want, but these wire wraps withstood many mechanical vibrations and continued to work until decommissioned.

[k4kyv]

Yeh, I hate to take good connections apart later, but I still believe in the old military version of connections.  Even mine are good for only so many G's.

Exactly what pulls apart when non-mechanically sound, but properly soldered joints are subjected to vibration and G's? In ordinary chassis work, I have never seen anything except cold joints and "rosin" joints pull apart even when I deliberately tried to do so. The wire would pull in two or the solder lug would pull out of the terminal strip or tube socket first.

OTOH I have seen solder jobs where the solderer was excessively skimpy with solder, and just barely applied enough to tack the components in place, and you could literally pull the wire loose.

If the wire shifts before the joint cools, leaving that crystalline texture, it can be repaired by re-applying heat, and adding a little more solder if necessary.

One place you DO want a solid mechanical connection before soldering is on antennas.  I don't like to use lead/tin for antenna work because the solder tends to deteriorate in the elements. NEVER use lead/tin for ground connections, radials or other applications where it will contact the soil.  My experience has been that in about a month, the soil minerals combined with moisture turn the solder into a white powder and the connection literally falls apart. Instead, I use silver alloy brazing rods available from plumbing supply shops, heated with Mapp Gas. The brazed connections in my 28 years-old radial system are still as good as the day I made them.

Here's an interesting article from 2005 regarding tin whiskers.
http://mae.pennnet.com/Articles/Article_Display.cfm?Section=ARTCL&ARTICLE_ID=238657&VERSION_NUM=2&p=32