mining motherboard for parts

I think you're wasting your time. Unless you're a self-made millionaire and have nothing better to do. This is the era of Digikey and cut tap and digi-reels. The minimum order is about 32$, and you can get a lot of parts for that. I mean how much is your sanity worth if a circuit doesn't work because you tried to save 30$ by pulling parts off boards?

But if you insist, at least get two irons so you can melt both ends at the same time, or get a forked tip. I have three irons plus a desoldering iron, with all kinds of tips.

When I remove parts from boards I repair, I throw them out. There's just no sense in keeping them around.

What part values do you need? If you're really hard up, perhaps I can send you some. I actually need to clean up the place...

Quickest way I know is to clamp the board vertically in a vice, heat it with a hot air gun, (paint strippers work well) and brush them off at the same time.

A proper hot air rework gizmo is TONS easier. Sparkfun has some videos in their tutorial section (and I'm sure there are a bunch more how-tos out there, but Sparkfun's are the ones I'm familiar with). The videos mostly show TQFP-style rework; two lead and SOT-23 devices are, natch, much easier.

The resistor and capacitor kits from Digikey et al. are good to have on the shelf but (aside from the practice) you can get some devices and sizes that are handy for prototyping/proof-of-concept/curiosity.

"Jon Slaughter" hath wroth:

How to remove SMD parts efficiently.

1. Clamp one edge of the MB in a bench vice.
2. Place a cardboard "target" box opposite the components.
3. Melt everything with a propane torch. Some practice will be needed to find the correct flame width, temperature, melt time, etc. Plan on wrecking a few boards and parts before you get it right. Some boards work better by torching the side opposite the components.
4. If the components were glued to the MB before soldering, forget it.
5. Pull back on the MB and release. The parts will fly in the general direction of the cardboard box.
6. Large parts, such as heat sinks and electrolytics will need to be removed manually.

I should do a video of this the next time I scrap some boards.

The technique I use is to hold the PCB in my left hand, with a welding glove on, a hot-air gun in the other and play it on the board, when the solder starts to melt, a sharp rap on the ground nets a pile of SMD parts. It only takes a couple of minutes to strip most of a board, I don't bother fighting with hard-to-get parts unless they are highly desirable ones. Sorting them into categories takes the most time, but a bright light, and a magnifying visor makes it a tolerable task.

I have never found a bad one yet from this removal technique, and while I don't use a lot of them, they have proven mighty handy when I need something NOW.

I just ordered 40$ worth of mosfets.. and forgot to order smt resistors and caps(well, I was going to use TH but decided I might as well try smt)... took a week to get the parts. So now I'm suppose to wait another week to get a few about 10 resistors and 10 caps(of course I would order more but thats all I need right now)?

I just don't see any neet to waste all those parts on the MB. Maybe its a bit waste of a time but otherwise its quite exiting(joking of course).

Heh... well, if your giving them away for free...

You should! I'd like to see that method in action ;)

Yeah. I was going to order some from digikey but forgot(I just ordered a bunch of mosfets cause I didn't have any except for power). Didn't feel(and don't feel) like waiting a week to get the parts when I just need a about 10 resistors and a few caps.

Thanks for all the replies. Seems there are much better ways to do this.

I still have a few questions(probably wasn't clear on the first post).

Do the smt components like resistors and caps have metal tabs/interfaces to the components that I'm probably ripping off when I use force(I was thinking maybe the heat was traveling through the board/component and someewhat melting the other side but maybe not)? There are a few that I was able to save by just using enough force to life one side of the smt just enough from its pad then desolder the other side but a lot of them have just solder on one side and nothing on the other(as far as I can tell).

It seems that either a torch or hot air gun is the way to go. What wattage should I be looking at for the gun?

Lastly, what is the average max power rating for those smt resistors(approximately)?

Thanks, Jon

Oh, and how bad will the fumes be?

"Jon Slaughter" hath wroth:

Sure. The only problem is that I have to keep the down range area clear so that the hot solder spray doesn't do any damage. The cardboard box catches most of the solder and parts, but there's always some solder that manages to fly in the wrong direction. I should also mention that safety goggles are a must for this exercise. Also, a UV filter for the camera lens.

I found a few web pages showing various ways of doing such salvage. Most use a hot air gun, which I find too slow:

Using a cigarette lighter:

There are some other desoldering videos on YouTube.com. Search for keyword "desolder".

A WEEK!??? Do you live on Jupiter? I can order at 6pm and have the stuff in the next morning! This is the Digikey at digikey.com we're talking about?

So how about, I don't know, pre-emptively buying a nice kit of parts to stock your lab?

I mean look at it from my point of view, you're saying that keeping a huge stash of dead electronics around, and then trying to find the part you need, then removing it, is somehow easier than having drawers with labelled, new and known-good parts??

It's obvious you're interested in some sort of romantic and emotional vision of the hacker/scrounger...

Imagine you went to a restaurant were the chef worked like that. He'd keep old dirty plates around for months, and just scrape off bits of dried and rotten food at random till he gets what he wants.

Hungry??

snip

Most are probably thin films 0.1W.You can get an assortment at Digikey, 500 hundred for $17 (805). Digikey orders take two days. Newmarket has overnight, here in Canada anyways.

Yup, if there's no metal cap remaining it's going to be, ah, harder than usual to solder it to the new pads. ;-)

I ended up with one of these guys (got a good price) and have been quite pleased with it.

If you're going for the "remove 'm all at once" method, just get a good paint stripper air gun from the local hardware store and let 'er rip.

I'll probably do that next time I order. Right now I think I'll be able to use what I got off the MB.

Thanks, Jon

Thats what I got. I just removed about 100 pretty quickly. I'm hoping that the 1000 oF isn't to much ;/ only takes a few seconds to melt the solder then I just scrap them off. The biggest problem is that they tend to clump together but I figure I can deal with that after the fact.

I think that will cover everything I need.

Thanks, Jon

"Jon Slaughter" skrev i en meddelelse news:QNqQi.4597$ snipped-for-privacy@newssvr23.news.prodigy.net...

That once you get the components off you can make a nice handle for several knifes out of the board material - you do need a mask when grinding it into shape ;-)

a big soldering iron bit, very well wetted, hold on one side of smd for a while, then quickly move to other side, usualy there is glue holding it on the board, so you need to make sure the solder on both sides of the smd are molten at the same time then apply some force.

if both sides arnt molten the device will most likly be ruined.

sometimes the heat transfer through the smd is enough to keep the other side molten.

some devices particularly ceramic caps have a very high failure rate when re used.

devices with many leads are difficult, a trick I picked up is to thread some fine copper wire

Well, just to be Debbil's Advocate here, some years ago, I was a video game/pinball machine/jukebox/foosball table repairman. While I was working there, Universal Electronics introduced the Mr. Do! conversion kit. At the time, a new video game ran about $2500-$3000; but the customers could bring in their old games that weren't making any money (pong, space invaders, asteroids, etc) and have it converted to a Mr. Do! for about $300.00. New marquee, new laminate on the sides, maybe refurb the control panel, and swap out the board - the new monitor was optional at extra cost.

And when we swapped out the board, typically the customer would say, "Well, what am I going to do with it?" so I would take it home and strip it. I got a handful of Z80s, 6800s, 6809s, 6502s, RAM, EPROM (well, they usually kept their EPROMs), and a big pile of TTL logic.

I used the "blowtorch" method. Clamp a vise-grips on the part, and hit the other side with the torch. Usually the board got scorched, but I didn't care about that.

Of course, I wore safety goggles, but didn't do anything about the fumes from the burning board; being a smoker, it didn't bother me much. :-) (well, I'm pretty sure I opened the window.)

But I wouldn't do that with surface mount - for one thing, how do you tell which is which? "Gee, here's one marked '3'!" And I wouldn't do it on a known defunct board - which part is the dud?

I built a keyboard controller and a "TV typewriter" out of all scrounged parts, except for the keyboard itself, the monitor, and the perfboard. :-)

Cheers! Rich