Removing relay without damaging pcb (plated through holes)

[Michael A. Terrell]

80/20? 60/40? What kind of solder are you talking about? Eutectic
tin/lead is 63/37 and used in both hand and automated soldering.

Really? I want proof. If 63/37 is the only solder used, please
explain to everyone WHY there are so many different solder alloys sold
for electronics. I have NEVER seen a wave solder machine filled with
eutectic solder. 80/20 was used in all the wave solder machines I've
seen because it has a higher melting temperature and goes from liquid to
solid almost immediately.

I shouldn't have included the reflow process, because there is too
damn many low temp plastics used in SMD components these days. Earlier
boards only had the resistors, capacitors and semiconductors reflowed,
which could use higher temperature solders. Now there are lots of
crappy SMD connectors, pots and relays that require a lot more work to
create a workable reflow profile for the oven. Every board design has
to be evaluated, and a custom profile created for that assembly. We had
over three hundred profiles stored on the Heller oven when I left
Microdyne, all sorted by assembly/stock number.

They kept changing the paste solder for reflow, and replaced the two
original ovens with the computer controlled Heller so I couldn't keep up
with all the variations in alloys, ball sizes and fluxes. It seemed
like as soon as we found paste solder that worked right, we couldn't get
more of it, and had to start looking again. I know that the solder I
used for rework was .015" 60/40.

http://www.kester.com/en-us/technical/alloy.aspx is a chart of alloys
currently available from Kester. They list 13 various tin/lead alloys.

--
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

 

[Jim Yanik]

I've often found that in a pinch, you can wick the solder out, re-fill
the holes with new solder, re wick the holes. Sometimes the
re-filling process can reflow the whole joint instead of wicking out
the top half and the bottom never gets hot enough. Of course, not
perfect, and should be done on a scrap board.

Steve

maybe use some very low melting point solder like ChipQuik?
And a vacuum desoldering tool.

 

[Smitty Two]

Really? I want proof. If 63/37 is the only solder used, please
explain to everyone WHY there are so many different solder alloys sold
for electronics. I have NEVER seen a wave solder machine filled with
eutectic solder. 80/20 was used in all the wave solder machines I've
seen because it has a higher melting temperature and goes from liquid to
solid almost immediately.

I shouldn't have included the reflow process, because there is too
damn many low temp plastics used in SMD components these days. Earlier
boards only had the resistors, capacitors and semiconductors reflowed,
which could use higher temperature solders. Now there are lots of
crappy SMD connectors, pots and relays that require a lot more work to
create a workable reflow profile for the oven. Every board design has
to be evaluated, and a custom profile created for that assembly. We had
over three hundred profiles stored on the Heller oven when I left
Microdyne, all sorted by assembly/stock number.

They kept changing the paste solder for reflow, and replaced the two
original ovens with the computer controlled Heller so I couldn't keep up
with all the variations in alloys, ball sizes and fluxes. It seemed
like as soon as we found paste solder that worked right, we couldn't get
more of it, and had to start looking again. I know that the solder I
used for rework was .015" 60/40.

http://www.kester.com/en-us/technical/alloy.aspx is a chart of alloys
currently available from Kester. They list 13 various tin/lead alloys.

Yes there are many alloys of solder. 60/40 was the standard for some
time but was replaced 20 years ago by 63/37. That is the only tin/lead
ratio that is eutectic and has been the industry standard for all
soldering AFAIK, for at least 20 years. You may have used 80/20 for some
reason, but it certainly isn't eutectic.

 

[Michael A. Terrell]

Yes there are many alloys of solder. 60/40 was the standard for some
time but was replaced 20 years ago by 63/37. That is the only tin/lead
ratio that is eutectic and has been the industry standard for all
soldering AFAIK, for at least 20 years. You may have used 80/20 for some
reason, but it certainly isn't eutectic.

I never claimed that it was.


--
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

 

[Smitty Two]

I never claimed that it was.

Well, you wrote:

"80/20 is used for wave soldering, because it has a very narrow
temperature range where it is in a plastic state. this reduces cold
solder joints, by not giving the leads a chance to move while the solder
passes through this state."



If that isn't the definition of eutectic, than you have my apology for
being wrong yet again.

 

[Al]

Well, you wrote:

"80/20 is used for wave soldering, because it has a very narrow
temperature range where it is in a plastic state. this reduces cold
solder joints, by not giving the leads a chance to move while the solder
passes through this state."



If that isn't the definition of eutectic, than you have my apology for
being wrong yet again.

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

 

[David]

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]

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

Exactly: "Non-eutectic mixtures have a melting or softening range." This
is what causes the "cold solder" problem when components are moved
slightly as the solder cools. In the eutectic (63/37) alloy of tin and
lead, the melting temperature and the freezing temperature are the same.
THAT is the relevant part of the definition as it relates to soldering.

Sheesh, learn how to read and comprehend your dictionary.

Jon

 

[Smitty Two]

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

David

That's your high tech military alloy, 104% total. Not allowed for
commercial applications. But you're a lot closer than the dictionary
reader. 63 tin, 37 lead.

 

[Jim Yanik]

Exactly: "Non-eutectic mixtures have a melting or softening range."
This is what causes the "cold solder" problem when components are
moved slightly as the solder cools. In the eutectic (63/37) alloy of
tin and lead, the melting temperature and the freezing temperature are
the same. THAT is the relevant part of the definition as it relates to
soldering.

Sheesh, learn how to read and comprehend your dictionary.

Jon

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.

 

[David]

That's your high tech military alloy, 104% total. Not allowed for
commercial applications. But you're a lot closer than the dictionary
reader. 63 tin, 37 lead.

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

David

 

[Ron M.]

Make up a pyramidal truncated frustrum (Google) out of 4 pieces of tin-
plate, wired together. Mask off that area around the relay, with the
frustrum temporarily wired to the board. Mount board firmly in vice, near
the relay. Pull and wriggle the relay when you apply heat from a hot-air gun
directed into the frustrum.
If you don't believe it will work try the technique with plated thru comps
on a scrap board first. The hotter the air and quicker you are the better,
if board starts to discolour there is probably some other mechanical
restraint.

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

 

[Steve]

maybe use some very low melting point solder like ChipQuik?
And a vacuum desoldering tool.

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.

 

[neon]

s solder socker and braid will do it a min of 50w soldering iron is required. after you remove most of the solder grab the pins and break the cold solder connection sometimes you may melt the solder and sharply hit it on the table to shake the solder off make sure that that doesn't cause more damage. clean soldering iron is a must.

 

[Jim Yanik]

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.

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.

 

[Steve]

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.

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

 

[Al]

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

 

[Michael A. Terrell]

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.

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

 

[Steve]

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.

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

 

[Michael A. Terrell]

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