Need advice on soldering

[dZeus]

I need some input on a soldering exercise. Knowing that some murcers here have quite a bit of experience in this sort of stuff I guessed it's the right place to ask these questions.

Here's the situation:

I would like to swap memory ICs on some of my ultra low-power servers (Linksys NSLU2). Apparently you can swap the 2x 16MB memory ICs with 2x 32 MB from PC133 DIMM donor PCBs. On the software side the support for the increased ram is very easy. For me the challenge lies in the hardware part.

I've got a simple Weller 50W adjustable temp soldering station. I've done through-hole chip unsoldering/resoldering with it, but never SMD type work (which is what is needed here). From some youtube how-to videos I've learned that people seem to use a hot-air station or portable butan-powered soldering iron to desolder these microchips. See here.

So right now I tend to do the following:
- acquire/buy a butane powered soldering iron that doubles as mini blow-torch. Like this one. I've noticed that these things are a lot cheaper in the US than over in continental Europe where I am. Should I import one?
- acquire a vacuum-suction device that can withstand high temperature of heated up ICs, to aid in lifting them up when the legs of one side of the IC has been heated to a temp where the solder liquifies.
- acquire one of these strips that absorbs excess solder when heated up (as shown in the video).
- acquire non-oxidizing flux
- practice the required techniques on electronic waste that serves no other use. Requires a bit of dumpster diving to retrieve some willing PCBs.

Are these the steps the knowledgeable ones of you would recommend? Thanks in advance!

[dZeus]

after seeing this video, I'm starting to think that my solution is way overkill and too expensive. These SMD removal kits are less than 20 USD and might include all I need (maybe get some extra flux for resoldering and this strip to absorb excess solder).

[degrub]

desoldering is easy compared to soldering the new components. The temperature at the solder point has to be precisely controlled and the heat flux limited . Otherwise you overheat the connection of the lead at the silicon and damage it. You need tips and gun designed for SMD work. And a steady hand.

[UtwigMU]

I outsource all soldering. I take all the stuff such as broken monitors, motherboards to some person and he fixes everything for ~30 EUR.

Also there is reflow repairs in UK: http://www.reflowrepairs.co.uk/ I did business with them once and they were very professional.

[Greebe]

Chemtronics desoldering braid, a razor knife, soldering station w/ appropriate tips and additional solder / flux. It's not a biggie if you have it on hand (me), but costs add up fast, especially in small "hobby" quantities. Taught prescision soldering and specialized in SMD repair yada yada yada if ya need me Frank, just yell

[dZeus]

Thanks for the advice Mike.

I've noticed there are several versions of the Chemtronics desoldering braid. This page with produce listing shows them. Some further questions on the differences between them:
- can the difference between SD and non-SD versions be summed up as the lack of need to discharge any static charge buildup on the soldering braid?
- is the lead-free version of the soldering braid just a version to comply with RoHS or is it the only version of the braid that can deal with removing lead-free solder?
- do you recommend the Rosin type, as it contains non-corrosive flux, or is cleaning the regular version with alcohol just as easy?

Thanks!

[Greebe]

Thanks for the advice Mike.

I've noticed there are several versions of the Chemtronics desoldering braid. This page with produce listing shows them. Some further questions on the differences between them:
- can the difference between SD and non-SD versions be summed up as the lack of need to discharge any static charge buildup on the soldering braid?

That about sums it up. The original desoldering braid was a standard white plastic with the potential to zap, not that it does. I've never seen it happen, to myself or the other hundreds of techs I've known. Our arguement is this, if you are holding the braid in your fingers, like one does 99.99% of the time and you yourself is neutral charge, then SD is negated.

- is the lead-free version of the soldering braid just a version to comply with RoHS or is it the only version of the braid that can deal with removing lead-free solder?

Both, tho the original will still remove the RoHS alloys, the newer formula works a tad better for non lead based solders.

- do you recommend the Rosin type, as it contains non-corrosive flux, or is cleaning the regular version with alcohol just as easy?

Rosin type only, alchohol is for cleaning only. The flux (organic or inorganic) is not a cleaner, but rather acts to reduce the surface tension of the melted metals and the circuit traces, copper, tin coated, silver plate, gold plate, make no difference so that the solder flows... that wonderful wicking action of the soldering braid works this way + capillary action

Thanks!

You're welcome

P.S. I've always found 'tinning' the desoldering wick with low eutetic leaded solder (62/38) paste or very fine gauge wire type helps alot, and or adding flux with a brush directly to the componets legs first. This will reduce the time heat is on the part to be removed, solder will flow alot faster. If the solder to be removed is stubborn, reflow it with reg leaded solder. The soldering tip I use most for this task is 700f beveled with a oval contact area of say,... 3mm x 5mm. Can lay the braid across the legs, draw the soldering tip across the legs in a wiping motion and get 99% on the first pass.