Removing relay without damaging pcb (plated through holes)

Defintion of eutectic:

"The lowest temperature at which a mix of two materials will melt. Often the temperature is an anomaly, that is, it is much lower than the melting temperatures of only slightly different mixtures. Lead-tin solder is an example. Lead melts at 327C, tin at 231C. The lowest melting combination is 67 lead, 33 tin (180C). Non-eutectic mixtures have a melting or softening range. Such mixtures do not flow well until thoroughly heated past the softening range."

Jeesh, get a dictionary.

Al

I thought it was 67% TIN and 37% lead.

David

Smitty Two wrote in news: snipped-for-privacy@news.phx.highwinds-media.com:

That is how Tektronix explained it to it's techs when they converted from

60/40 to eutectic 63/37 solder.Eutectic has a narrower plastic range. Now,that is for repair work,I do not know what TEK used in its wavesoldering lines.it makes sense ot use a eutectic alloy on them,too,as motion would have a greater effect on a partially soldified joint.

for REMOVING that relay,I'd use ChipQuik or similar alloy,the joint would melt at around 200 something degrees F,MUCH less chance to apply too much heat to the PCB.

You would think that solder makers would offer an alloy similar to ChipQuik for this purpose,at a more reasonable price,maybe in a 1/2 lb spool.

--
Jim Yanik
jyanik
at
kua.net

(Blushing) I guess spell checkers do not perform arithmetic checks. Thanks for correcting this.

David

We just usually use the hot air bonder. Sorry had to go there.

on

I got lucky and we have a nice Pace desoldering station at work, makes easy work for most items. But, I still have quite a few rolls of different sized wicks for that fun special occasion, or SM work.

Steve wrote in news: snipped-for-privacy@4ax.com:

In TEK's SMD training class,we used a newer Pace desoldering system(than what we had back at the field office),and were told use of wick(or Soldapult) would lift pads,as wick requires more heat to be applied for a longer time. The Pace tip was a lot different for SMD desoldering work.

--
Jim Yanik
jyanik
at
kua.net

We have a very small budget where I work, the smd tip we have is just a very fine point tip instead of one of the chip-size special tips. I mainly use the desoldering tool for thru-hole items, especially tedious ones like 40 pin IC's. I have lifted a few SM pads, but for the most part as long as I'm careful the fine tip and good quality wick do just fine. I've used tech-spray no clean wick with some good results. I had quite a few rolls of some cheaper wick, and the flux on the wick must have gone bad, the solder just doesn't flow to the wick anymore. I've heard solder and wick have a shelf life, I guess I didn't used to believe it until I saw it first-hand.

Steve

You might be able to reactivate the wick using electronic grade isopropyl alcohol. Just put a drop on a length, wipe it clean and try it out on a scrap board.

Al

All that will do is remove even more flux.

Get some good liquid RMA flux (I use Kester 1544) and wet wick it. Touch the end of the wick to the flux, and use it that way. It will do less damage than dry wicking. Also, leaving about 1/8" of used wick when you trim it makes it work better.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

I'll try it. May be worth a shot to save a few bucks. Steve

I've only bought about 15 feet of solder wick in the last 20 years but I've made, and used, thousands of feet from scrapped bare copper braided Cable TV converter cables that I replaced.

I could pull the two insulated wires and paper filler out of the braid, then pull out the braid from a 21 foot cable. By the time it was flattened out and wound on a spool, it was a little over 25 feet by approx. 3/16". I had about 500 bad cables when I moved to Florida, 20 years ago. :)

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Carefully destroy the relay without damaging the circuit board so that you have the stubs of the leads still sticking out from the PC board, then solder to them. if you're lucky, there'll be enough leads exposed so that you can just cut them and leave enough stub.