REMOVING SMD components from Circuit boards What's the trick?

[Lemosteam]

Ok de-soldering experts out there.

The Bachmann Heavy Mountain decoder thread discussing removal of capacitors and chokes led me to ask the subject question.

I have tried to remove / salvage SMD components & LED's from circuit boards, etc, and found it difficult to de-solder both pads at the same time.  is there a trick that does not result in lifting or damaging the copper traces or ruining the component itself?

Do you de-solder and slide a thin, non-solderable material underneath to separate one side while you remove the other?

[RBrodzinsky]

The biggest "trick" is to realize that most manufactured boards these days are going to be EU ROHS compliant, which means the solder is lead-less.  These typically require a higher temperature to get the solder to flow, which, as you noted, can cause damage to the traces.

I typically take my soldering iron up to about 800F, and use a small conical wedge tip, just cleaned but with no added solder to it. I put the edge against the component, with the conical cut surface down towards the board/pad, and gently push into the component. This tends to flow the solder and lift the component a bit.  Repeat on other side.  I then use ESD/non-conductive tweezers to pull the component; I may have to touch both sides with the iron, again, but everything should lift easily.  If there is a lot of solder on the board, I will also use a solder puller to remove the excess prior to the gentle pushing on the component.   Under no circumstances do I leave the iron's tip on the board for more than a couple seconds at a time.

Hope this helps.  Does take practice.

[C855B]

Pros use a hot air rework station. Like a hot air gun 'cept with a point nozzle. Good ones are expensive (Hakko is a pro brand, >$500 for many models), but there are <$100 versions of questionable heritage. But even with the good ones, there's no assurance you're going to be able to recover the component, either. In the pro world, SMD components are considered disposable, costing far less to replace with new versus technician time. Basically it's all about saving the board.

Also, there are soldering tweezers that will work for small 2-lead components like resistors and caps, but I'm not sure about recovering semiconductors safely.

Mr. SMD (@peteski) may have some tricks, as well.

[jdcolombo]

A pro soldering station, like the Pace ST50 with TD100 handpiece that I use (recommended by Peteski, BTW), will have a variety of tips for this kind of work. 

A list of these desoldering tips for the Pace is here:

http://www.gotopac.com/products/solder-rework/desolder-nozzles.html?manufacturer=1286

If you are going to do much of this kind of work, then I'd strongly suggest going the professional route.  If all you need to do is desolder a couple of components on a once-in-a-lifetime job, then Rick Brodzinsky's procedure will work fine if you are careful not to overheat the part (if you want to re-use it).

John C.

[railnerd]

another trick is using two soldering irons..

but I highly recommend Rick's suggestion to start.

-Dave

[Mark W]

If neither Rick's method, nor two soldering irons works, a third last-resort option is mechanical removal. Instead of removing the SMD from the board you remove the board from the SMD. 

I've done this just once by using an xacto blade to "carve out" the solder pad from the board, then filed it off from the SMD. 

But as mentioned, unless you're in a pinch and just need a quick part without waiting days for shipping of a fresh one, not worth your time harvesting most SMDs.

[mmagliaro]

I never really thought about this.  But I just happened to do it the other day, and here's what worked for me.
Slip a #11 Xacto point gently under the component.  You can usually get it at least wedged in along an edge.
Heat one pad.  The part will flip up a little.  Then heat the other size while you hold the part with tweezers and pull it off.

It did not seem to harm anything to slightly pry it up like that while heating one side.  (And yes, the part did work after I removed it)

[railnerd]

I never really thought about this.  But I just happened to do it the other day, and here's what worked for me.
Slip a #11 Xacto point gently under the component.  You can usually get it at least wedged in along an edge.
Heat one pad.  The part will flip up a little.  Then heat the other size while you hold the part with tweezers and pull it off.

It did not seem to harm anything to slightly pry it up like that while heating one side.  (And yes, the part did work after I removed it)

That will work…  as others have mentioned, tearing up the PCB is also possible, so be gentle.

[peteski]

Most of the things I was going to suggest have already been covered.

I do have a complete PACE rework station including hot air jet, solder extractor,  and tweezers with all sorts of tips.  Back in the '90s I took the official PACE SMD rework course (and have a certificate to prove it). 

It is true that most electronic circuit boards manufactured in the last 10 years or even earlier use a lead-free solder due to the RoHS Directive.  The new solder while environmentally friendly, it is a pain to deal with by hobbyists.  That solder is a real pain to deal with.   It has a much higher melting point than the standard 63/37 electronic solder and it results in crusty looking dull joints.

As for unsoldering small SMD components with 2 solder pads using standard hobbyist soldering iron, I put some solder paste or flux (the electronic type) on the pads and add more solder to the existing solder. Build it up as much as possible. That will make it easier to melt the solder under the component. Apply more paste or flux and then alternately and quickly heat up and melt each blob of solder eventually they will both loosen up enough for the component to come off with one of the blobs.  Of course if one has 2 soldering irons then that works much better.   Once the component is removed, add more paste or flux to the solder pads on the board and using solder wick and iron clean the solder off.

As far as reusing the unsoldered components, I don't like to do that. The heat-stress form desoldering them not using the proper tools can damage or weaken many of them.  The semiconductors (like LEDs, diodes, or transistors) are most delicate. Then the ceramic caps are also sensitive to heat stress. They are sandwiches of hundreds of very thin slivers of metalized ceramic and heat can fracture them. Resistors are most robust and those can be freely reused.

[Lemosteam]

So this is not so much about saving the components, it is mostly about preventing the destruction of the pc board.

Here is the board in question. I want to reuse the board for an LED replacement extension wires in my K4 kit by soldering on the remaining pads.  I destroyed the first one even after using a wick, but I was pretty clumsy. The issue the first time was the pad lifted off the board.

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[peteski]

Since the SMD component's metal pads are pretty much in contact with the copper pads on the PC boards, solder wick will not get all the solder out from under the component. The extra solder method I described will alowo you to easily remove (melt off ) the component and then you can clean the solder pads on the PC board. But too much heat applied for too long  will delaminate the copper from the PB board. That is the other problem with the new lead-free solders. Their higher melting temperature makes you use a hotter iron which can delaminate the copper pads.  Mixing some lower temperature solder with the the lead-free stuff on the pad and using flux allows you to wick the solder quickly (hopefully not affecting the bond between the pad and the PC board.  If you have a temperature controlled iron apply the solder blobs at about 720 degrees (and make sure the low temp. solder mixes with the lead-free stuff)., then for wicking the solder off the pads put more flux on and use the iron at around 650 degrees.  Clean and tinned tip and lots of flux is a key to success.

[Lemosteam]

Thanks Everybody!

[Sdynamo]

Has anyone purchased one of the knock off rework stations on eBay?  I just looking to remove the SMD LEDs on the new Lok Sound boards to gain more functions.  I'm not planning to use it for an real production work.

[Greg Elmassian]

Bought a $250 one, works ok, not as nice as the professional ones, but cheap enough and works well enough.

Greg