Removing relay without damaging pcb (plated through holes)

[[email protected]]

I have an old project where a relay is oddly stuck in a state with the
common rail connected to the normally open contact. I can only assume
that the two connections fused together during a high-current
transient. The relay breaks a connection between an audio amplifier
circuit and a subwoofer. I think my only choice is to replace the
relay. There is however a problem where the pins of the relay are
soldered to plated through-holes. This is making the relay nearly
impossible to remove without risking damaging the pcb. Does anyone
have any neat tricks to remove such a component safely?
Thanks

 

[Dave Plowman (News)]

I have an old project where a relay is oddly stuck in a state with the
common rail connected to the normally open contact. I can only assume
that the two connections fused together during a high-current
transient. The relay breaks a connection between an audio amplifier
circuit and a subwoofer. I think my only choice is to replace the
relay. There is however a problem where the pins of the relay are
soldered to plated through-holes. This is making the relay nearly
impossible to remove without risking damaging the pcb. Does anyone
have any neat tricks to remove such a component safely?

If using a desolder tool and solder braid still leaves it stuck it's often
best to carefully wreck the component so you can treat each pin
individually.

 

[N Cook]

I have an old project where a relay is oddly stuck in a state with the
common rail connected to the normally open contact. I can only assume
that the two connections fused together during a high-current
transient. The relay breaks a connection between an audio amplifier
circuit and a subwoofer. I think my only choice is to replace the
relay. There is however a problem where the pins of the relay are
soldered to plated through-holes. This is making the relay nearly
impossible to remove without risking damaging the pcb. Does anyone
have any neat tricks to remove such a component safely?
Thanks

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.

 

[[email protected]]

I have an old project where a relay is oddly stuck in a state with the
common rail connected to the normally open contact. I can only assume
that the two connections fused together during a high-current
transient. The relay breaks a connection between an audio amplifier
circuit and a subwoofer. I think my only choice is to replace the
relay. There is however a problem where the pins of the relay are
soldered to plated through-holes. This is making the relay nearly
impossible to remove without risking damaging the pcb. Does anyone
have any neat tricks to remove such a component safely?
Thanks

There is only one way: chop the relay up until you can get to each
pin, and desolder those individually.

I however would open the relay and file the contacts, far easier
option.


NT

 

[N Cook]

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.

As it happens, the last week I've been working on industrial boards with
plated-through soldering. Thick board so only tips of IC leads protrude,
very thin signal traces, traces to tiny pads on both sides of boards of same
pin in some cases and plated vias under ICs as well. I know if i'd used
"proper " vacuum assist desolder or butcher-and-remove single pins , many of
those traces/pads would have dislodged.
I had to sharpen the points of my large adapted circlip pliers to get the
extra purchase on the ends of these 14,16, and 28 pin ICs. Not one dislodged
track using a paint-strip hot-air gun. Next time i'll have to take some
before and after pics for the doubting thomases.

 

[Smitty Two]

As it happens, the last week I've been working on industrial boards with
plated-through soldering. Thick board so only tips of IC leads protrude,
very thin signal traces, traces to tiny pads on both sides of boards of same
pin in some cases and plated vias under ICs as well. I know if i'd used
"proper " vacuum assist desolder or butcher-and-remove single pins , many of
those traces/pads would have dislodged.
I had to sharpen the points of my large adapted circlip pliers to get the
extra purchase on the ends of these 14,16, and 28 pin ICs. Not one dislodged
track using a paint-strip hot-air gun. Next time i'll have to take some
before and after pics for the doubting thomases.

--

I'm not one of the doubting Thomases. Hot air works well. So do the
other methods, that you doubt. It's all about technique and finesse. The
professional desoldering stations work extremely well when used and
maintained properly, and virtually not at all otherwise. Blame the
operator.

 

[CWatters]

There is only one way: chop the relay up until you can get to each
pin, and desolder those individually.

That's the way I'd do it.

 

[Meat Plow]

That's the way I'd do it.

That's the way I've done it.

 

[Marra]

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.

I would just leave it as it is rather than knacker the board

 

[[email protected]]

That's the way I've done it.

Any recommendations on how to "chop up" the relay?
Its a sealed plastic type.

 

[Michael A. Terrell]

Any recommendations on how to "chop up" the relay?
Its a sealed plastic type.

Are the pins smaller than the plated through holes. or are they a
tight fit? If there is any free space you can remove the solder, then
heat the pin till the solder melts and gently bend it loose from the
wall of the plate through hole. I've done it that way for decades, but
you should practice on a scrap board first.


--
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

 

[Spehro Pefhany]

On Thu, 31 May 2007 18:48:04 -0700, the renowned

Any recommendations on how to "chop up" the relay?
Its a sealed plastic type.

Sharp cutters like these: http://www.wassco.com/shearcutters.html

Cut into it from the top and keep cutting stuff away until just the
pins are left. Be careful cutting away the plastic bottom that you
don't scratch through traces or otherwise accidentally damage the
board.

If you have a *good* desoldering tool (with a vane pump etc.) it may
be possible to suck almost all the solder out of the holes so they
break away when wiggled without damaging the plated-through holes, but
it's not always possible, and it runs more risk even with good tools
and even if you have just cleaned the tool out.

 

[Al]

On Thu, 31 May 2007 18:48:04 -0700, the renowned


Sharp cutters like these: http://www.wassco.com/shearcutters.html

Cut into it from the top and keep cutting stuff away until just the
pins are left. Be careful cutting away the plastic bottom that you
don't scratch through traces or otherwise accidentally damage the
board.

If you have a *good* desoldering tool (with a vane pump etc.) it may
be possible to suck almost all the solder out of the holes so they
break away when wiggled without damaging the plated-through holes, but
it's not always possible, and it runs more risk even with good tools
and even if you have just cleaned the tool out.

I've used a Dremel tool to remove relays, as well as other components, by
cutting them to pieces, carefully, of course. Then I unsolder one pin at a
time. Unless you need to do failure analysis on the bad part.

Al

 

[[email protected]]

Which bit do you use? A grinder or a saw bit

 

[[email protected]]

Which bit do you use? A grinder or a saw bit

Cutting off the relay is the hard bit, as many have quite hefty bits
of steel in them. A cutting wheel in a die grinder (aka dremel) works,
but can be slow.


NT

 

[Ron(UK)]

Cutting off the relay is the hard bit, as many have quite hefty bits
of steel in them. A cutting wheel in a die grinder (aka dremel) works,
but can be slow.

My own method would be a good hot iron, plenty of solder braid and a lot
of patience.

Ron(UK)

 

[Steve]

My own method would be a good hot iron, plenty of solder braid and a lot
of patience.

Ron(UK)

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

 

[Ron(UK)]

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.

That`s true. One of the things novices do wrong is to wick off most of
the solder, but leave a little behind deep in the hole, that wont be
drawn up into the solder braid. Then they get impatient and try to rip
the component out damaging the board in the process.

There needs to be enough solder to easily wick up into the braid, and
the iron need to be hot enough to melt all the solder in the joint
through the braid or there`s a chance that pulling the braid away takes
some of the pad with it.

There`s as much an art to desoldering as there is to soldering. (IMO)

Ron(UK)

 

[Michael A. Terrell]

That`s true. One of the things novices do wrong is to wick off most of
the solder, but leave a little behind deep in the hole, that wont be
drawn up into the solder braid. Then they get impatient and try to rip
the component out damaging the board in the process.

There needs to be enough solder to easily wick up into the braid, and
the iron need to be hot enough to melt all the solder in the joint
through the braid or there`s a chance that pulling the braid away takes
some of the pad with it.

There`s as much an art to desoldering as there is to soldering. (IMO)

Ron(UK)

The solder used for wave soldering is 80/20 and has a higher melting
temperature. By removing what solder you can, then adding fresh 60/40
you move the melting point to somewhere in between, which then can be
either vacuum desoldered or removed with solder wick and a drop of
liquid rosin flux.

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.


--
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]

The solder used for wave soldering is 80/20 and has a higher melting
temperature. By removing what solder you can, then adding fresh 60/40
you move the melting point to somewhere in between, which then can be
either vacuum desoldered or removed with solder wick and a drop of
liquid rosin flux.

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.

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.