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I am working on surface mount circuit boards and having trouble removing components (through hole) due to the power and ground planes sucking away all of the heat from the soldering iron. Do you have a suggestion on what wattage iron I should be using?

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    \$\begingroup\$ Are you trying to preserve the board or the components? \$\endgroup\$ – Dave Tweed Jul 22 '14 at 13:44
  • \$\begingroup\$ What kind/ brand of soldering iron do you have? I've got a Weller WTCPT. It's got tips that have different temperatures and sizes. When I need a lot of heat I switch to an 800 (F) tip that is big and fat. So maybe not more power, but a higher temp and bigger tip. \$\endgroup\$ – George Herold Jul 22 '14 at 13:45
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    \$\begingroup\$ In that kind of situation I tend to pre-heat the area with my SMD rework hot air blower. \$\endgroup\$ – Majenko Jul 22 '14 at 13:52
  • \$\begingroup\$ Those are the cases where it is very nice to have a variable-temperature iron. It's impossible for us to tell you what wattage you need because we know nothing about what your board looks like. It's one of those things that you need to do some trial-and-error for in order to determine the correct wattage. \$\endgroup\$ – DerStrom8 Jul 22 '14 at 15:11
  • \$\begingroup\$ A temperature controlled iron normally has "excessive" wattage available, as it only heats to maintain temperature, unlike a cheapie where the temperature achieved is the one where input power and losses balance. The preheat ideas are good, but if you design boards try to include thermal relief on the through holes next time. \$\endgroup\$ – Chris Stratton Jul 22 '14 at 16:12
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I'm going to follow up what Some Hardware Guy had to say - your problem may not be one of too little wattage, it may be one of too little mass at the heated tip. The greater the tip's mass, the more thermal inertia it has; a tiny tip cools off very rapidly, while a larger time cools off more slowly. I have a 15W iron out in the shop that's so massive that it'd burn a hole right through a PC board. Takes a very long time to get it up to temperature, but desoldering parts with it is really really easy because no amount of solder on a PC board will cool it below solder's melting temperature.

That's really the crux of the problem. When solder goes through a change from solid phase to liquid phase, that phase transition requires far more energy than just heating it to the phase-change temperature... then it releases all that energy again as it shifts from liquid phase back to solid phase. Your iron needs enough mass to cross the phase change barrier.

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  • \$\begingroup\$ What is the name of this behemoth of an iron? \$\endgroup\$ – Sam Washburn Mar 8 '15 at 1:19
  • \$\begingroup\$ @Sam Washburn... sorry, I was "unstacked" for a while there. That big iron is a Jackson Standard. \$\endgroup\$ – TDHofstetter Sep 5 '15 at 22:45
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You need to maximize your heat transfer to the component to overcome the heat transfer into the planes. So a good iron that's 700+ with a wide tip, not the same pencil thin tip you may use for regular soldering of components. If you have hot air use the hot air to pre-heat the component then use the soldering iron and the hot air at the same time. Use flux or a flux pen if you have it.

If you don't care about the component clip the leads and destroy it, easier to take out one pin at a time.

If you have a solder sucker sometimes if you add a little solder to the lead then use it you can pull a lot of it out of the hole.

If you don't have a solder sucker, hot air, or a wide tip you can try making a large solder ball around the lead and keep the iron in there to keep it liquid. Then "gently" use needle nose to pull it out from the top side.

If you're going to be doing this a lot, for work they do make through hole de-soldering guns.

Everyone runs into this and pulling through holes that are tied to planes is a pita. That's why depending on what the component is, and used for, people will use thermal reliefs around the pin holes (basically little spokes that run to the plane).

Good luck

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Is the solder lead based or the ROHS stuff? I've found the ROHS needs hotter temperatures to desolder (700+). Make sure you are using solder wick or pump to get up all the residual solder you can.

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