Desoldering tips??

[rybowen]

Anyone have tips for desoldering the 8-bit eproms? I have a good Hakko station and my soldering skills are pretty good but I have trouble getting the last few pins out and usually end up clipping the legs off the IC...

Should I just cough up the $125 for a Pace desoldering station on ebay?

[deviousKA]

Get one of those blue spring loaded desoldering pumps, forget the brand but I think the model is AX-108. These and some desoldering braid will get anything.

The desoldering pump is nice and quick, always go around the pins with this first. The ones that are stubborn you can try some desoldering braid, or try flowing some new solder in and desolder pump it. Using the braid you have to put more heat down which isnt good, but its handy stuff.

Clean the clearcoat off of around the pins before you start, acetone works and I have also used non-clorinated brake cleaner, works the same and doesnt eat the board (but eats plastic be careful and quick).

Get some little picks, 45 degree angle like, to help pry the chip up. I use a dental scraper. These are also handy to shift the pins over to break them loose.

I have a Madell station which is the same as the hakko, Ive desoldered lots of eproms this way and never had to break a pin or trace, Im sure a desoldering station would be nice though.

[glacier985]

Yea those pumps work great and the braided wire isn't bad either. We use both at school to desolder chips from circuit boards. I learned that you jus have to be patient with it, go to quick, on slip and you can melt the board.

[rybowen]

I suppose it's just technique then. I've got one of the blue (Edsyn?) pumps and tons of solder braid. I always have trouble with the same pins (1, 28 & 21). It seems no matter how long I heat those suckers I can't get enough heat down there to loosen the solder around the leg. I've lifted a trace once, and had to jumper the board, so I'm reluctant to try a higher temp or more time... What temp are you using?

I use acetone first too, only I use a thin stainless shim to lift the chip & break the adhesive free.

[erich]

Sometimes when it just won't desolder cleanly I get out as much as I can then re-solder it with new rosin core solder. The new solder flows beter then the old crap and comes out much easier, while taking the old stuff out at the same time.

[max240]

^^ Thats my method, I always end up resoldering a few joints then re-desoldering.

[rybowen]

I do that too...

Maybe I'm not running the iron hot enough. What temp do you use? I've got it set at 600F most of the time for soldering.

[deviousKA]

I run mine at 800 most of the time desoldering, some would call that a bit hot but just move fast and let things cool. Some of the powers and grounds will be very difficult without going up with the temp.

If you have just a couple stubborn pins, pry up on the socket while heating those pins to let them slide a bit, sometimes helps.

[rybowen]

I'll try that on the next one. I keep scoring them cheap on ebay so I guess I'll have lots of practice.

[Mahasamatman7]

I used to be solder certified for depot level repair of military circuit boards. The guys still doing that have gone to the newer sophisticated stations but in the Good Old Days, we used 700watt irons made by Weller and varied the tip size for control of the heat transfered. The large tips of course when properly preloaded with a bit of fresh solder apply more BTUs per second to the joint. So for the type of joint in question you really want a tip a little bigger than a very dull #2 pencil. Work quickly never holding the tip to the joint more than a verbal count to 4 or 5. If you have held it that long, a full minute, preferably more rest time for that joint should be allowed so the board can dissipate the heat already applied. Fiberglass does not transfer heat very fast so you are essentially air cooling.
I have found that removal of solder can be quite a pain. If the board is in a free state, try to find a good "third hand" made for holding boards. It looks like a midweight wire frame vise with rubber jaws slotted to grip boards. Place the board vertically in the jaws and clamp so you can see both sides. If the chip leg is in a thru hole, heat from the chip side and use the solder sucker on the back side as soon as you see the solder liquify then immediately remove the heat.
As Devious stated sometimes go round robin while tugging at the chip a little at each heating of a pin and it will slowly work out. And the tip about fresh solder is very effective. The rosin core solder cleans the old joint and cleanliness allows the liquified solder to flow much better.
Soldering is really an art and always remember that it is like extremely critical welding. When you finish a good joint is gently filleted with no lumpy or frosty appearance. The copper traces actually start to dissolve into the solder of the joint. Chemically and physically soldering is a cool process. Of course keep good hygine in mind as you are working directly with lead. Eating, smoking, and scratching nads should wait till hands are washed with soap and water. That came out funny. Oh Well.
When you fininsh your work, use isopropyl alcohol and soapy water alternately with an artists brush cut to about 3/8 inch length to clean the rosin residue from the board, followed by drying in a location like the heat of a television overnight. Use a 10 power magnifier to check for solder splashes theat might cause shorts or incomplete joints. If it looks as good as factory, pat yourself on the back and test.

[rybowen]

Thanks for the great tips. I've modified my technique and now I'm doing much better.

Last night I did two more boards. I cranked up the temp to 800F and they came right out. Lost part of one pad on one board, but the other was perfect. Temp appears to be the key - I just needed to get more heat in there.

Have you ever seen a JWT-modified ECU? Scary soldering quality (or lack thereof). I sure hope the one I have is not representative of most.

Oh, and mahasamatman - I think I just saw one of those mil-surplus big ass Wellers you were talking about at my local surplus place.

[Doet]

hey guys i took 2 years in tech school on soldering what i notice that really helps when removing solder and soldering is that if you Don't tin the tip of the soldering iron with tin or solder it makes it more difficult to solder and de solder, what you do is get the iron hot and put piece of solder on tip of iron then take wet sponge,paper towel and smear the solder on the tip untill it stays on the tip. thats called tining your tips they also sell tip tinning stuff witch i never used before. but the tip got to be in good shape to to tin right. and also when you dont tin the heat cant get transfered to the solder and makes soldering a hole alot easyer. any question feel free to ask

[el tigre]

Ahhh, tinning like when you braze cast iron, got it.

[pmkls1]

I know this is an old thread but I figured I would add my 2 cents worth. I noticed that heat is definately the key. I use a butane iron from mac tools that is the equivalent of a 120 watt iron and once up to temp it melts the solder almost as soon as it makes contact. That allows you to move more quickly and the board doesnt absorb so much heat. Also, non-chlorinated brake cleaner will do just fine on the plastic on these boards. The chemical makeup of the plastic dictates wether it will melt when it comes in contact with brake cleaner and the type of plastics on these boards are impervious to it. I have literally hosed down a board before with brake cleaner as the computer had some damage from water intrusion and I needed to thoroughly clean it. None of the components suffered any adverse effects from the cleaner and it also made removing the prom much easier to have all of the sealant removed. Again just my 2 cents.

[qsiguy]

Well I'll add another post to this great old thread. Thanks for the brake cleaner idea, I'll have to try that.

I'll offer another desoldering method/tool. The other day I came across a tip to modify a shop vac, preferably a small one, and reduce the hose down to a about the size of a straw, in fact I think they even used a straw, lol. You use this for your desoldering gun. Heat up the solder and get this constant suction sucker near the joint and viola! I have yet to try this but there is no reason it wouldn't work. Also, compressed air can be used to blow the solder out in some cases.