Faced with the task of desoldering a couple of 40 pin DIP ICs, and my
> eternally poor desoldering skills using normal cheap tools, I've been
> looking into cheap DIY approaches to desoldering stations.
** If the IC is faulty - what you do is cut the pins off near the package and remove each pin from the PCB separately with tweezers and a fine, hot tip.
Clean up with a solder sucker or wick.
Then you can install a 40 pin socket or two, 20pin strips to the holes.
** IME there is no hazard to the chip inside a 40 pin DIL pak - you only heat one pin at a time, so the chip does not even get warm. The main worry I had was in pulling out plated through vias with the pins and damaging fine tracks on the PCB.
In a one case, after installing a socket, I retried the same 40 pin IC and the device ( a CRT monitor) worked perfectly.
In another, installing a new IC made the original fault worse than with the old one fitted - this was in a Yamaha R1000 digital reverb unit from the mid/late 1980s.
Warming the 40pin IC directly produced the fault - a huge noise in the sound.
Turned out, there was a design problem in all early production units.
The eventual fix was to replace 6 memory interface ICs with higher speed versions.
Indeed. You couldn't even buy the requisite raw materials (to make it yourself) in Australia for less than double that price.
But look at the number of sub-$1 (including postage) items on eBay, selling by the tens of thousands. Even if, as you say, they fell off the back of a truck, I still wouldn't put myself through the hassle of listing, monitoring, responding, packing and posting in order to make less than $1 per transaction - but there're obviously people who're happy to do it.
But that's the same model as the Ebay one I linked to.
More avoid getting electrocuted by the barrel or having the plastic melt at my fingertips. I'd be replacing the manual solder sucker with a vacuume pump anyway, as in the web page that gave me the idea.
Cheaper to get a replacement iron for a desoldering station like the one I linked to, then just use my existing vacuume pump and power supply.
Thanks, but if I wanted to spend that sort of cash, I'd probably already have bought the desoldering station from Rockby (if they have stock).
Depends how many you were making - look up the prices for plastic resin on Alibaba. You could get recycled stuff from within Australia too.
The real trick is the design, assembly etc. And in Aus, you'd have to meet safty requirements and anwser for those loose 240VAC wires.
Well, think of this scenario: You buy a thousand for $50 (factory rejects sold by workers, ghost runs etc.). Pay a couple of blokes $5/day each to pack and post 50 each day (slap on printed stickers and tape up the envelope). Then with $0.50 profit an item, you could grab $0.5x50 = $25 a day - $10 pay = $15
$250/20 = $12.5 a day earned by you, which would go a lot further in an economy where you can get by on $5. Of course there would be extra expenses, but I'm sure your average Chinese Ebay man would have a lot more than one item on the go.
What I don't understand so well is how some smaller sellers sell items for $6.00, but only move one or two a week (looking at the num. sold figures on Ebay). I guess they could be stall holders who are just on the 'net for some extra dough.
NOTE: I've never been to China and I don't really know the average wage for working class Chinese. I'm just imagining a scenario based on the single figure of item price and to me it seems possible.
I have one of those. Sort of works but to remove a 40-pin DIP from a PTH board you're going to be at it forever.
Remember that the button to release the sucker is way up the handle, so you wind up using a "dagger grip" (or two hands on the tool if you're a Tasmanian with a spare). It is a most awkward way which is a PITA on high pin counts.
If the O/P isn't trying to salvage the chip, (s)he should just cut the legs and remove them one by one. The amount of residual in the holes on the 40-pinner is going to make dislodgement after the first round of sucks far from easy.
Problem is that heat guns are relatively expensive too. But today I discovered another option along the same lines:
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I posted a comment about my idea that such hair straighteners could be used to desolder ICs. I'll have a look in some Op-Shops for old ones at the end of the week.
Well it works with leaded solder, but lead-free stuff (even doped) on a double sided board won't budge. I tested it on 14pin DIP ICs by holding the boards in a vice while prying the chips up from underneath with a small screwdriver.
I used some copper tape designed to be put around pots to stop slugs/snails (sold as "slugga") on the pads to make them conductive. It takes quite a while to tin something like this...
Tried it with a Remington S3500 I got from an Op-Shop (same model as used in the above webpage). Next step would be to see if I can make it get hotter, but Annoyingly I can't figure out how to take it apart, I got all the screws out that I could find and removed one of the heating pads, but the inside plastic panels are still held on somewhere under the hinge.
I also bought about six other hair straighteners and curlers (they were all either one or two bucks), but the other likely candidates have screws in particularly inaccessible places, so I haven't been able to begin getting into them.
So in the end it works, but only with leaded solder. Annoyingly the 40pin ICs I originally wanted to salvage are on a double sided board with lead-free solder, but at least I have a method I can use in the future.
I put off buying a desoldering station for a long time and regret it now. Such a useful tool, and desoldering a 40 pin IC cleanly in a about a minute and easily...
Not only that, I've got a few jobs desoldering and socketing chips for others to repair vintage equipment so it's paid for itself.
Out of curiousity, what are the two 40 pin chips you are/were trying to salvage?
The chips are PPI-8255 Parallel Interface ICs, a product of the early PC era.
I want to grab one off a control board I was given from an old Dot-Matrix printer so that I can build an IC tester as described here:
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I looked inside the highest wattage hair straightener I got to see if the temperature range could be extended. Unfortunately there's no info online about the chip used (likely some cheap clone because the "ST" logo is actually printed upside down). I'd probably end up just building a self-destruct funtion into the hair straightener anyway.
The best option is probably buying that spare desoldering gun at rockby and using my existing vacuum pump and transformer.
I haven't really started the project yet anyway because I want to work out a good method for making the PCB (I don't want to lay out that whole circuit on Veroboard like most other things I do). Last time I tried, with a small single layer board, I used almost all of a $45 transparancy film pack trying to get a passable result and ended up with traces like Swiss Cheese and some having to be cut with a Dremmel.
The printer I was using jams with photo paper (and a lot of normal paper for that matter), but I've actually got a few laser printers around so one day I'll have to try the full fleet. I read that the backing from sticker paper works, which could be good because I know where I could get some cheap, but I don't know how I'll go feeding it through a printer.
Extended heating of one pin can certainly damage a chip. That's why it a very good idea to get your tecnique down pat on scrap boards before you attempt to desolder a chip you want to keep.
I received an old Casio fax board today with 5 M5L8255AP-5's on it. I'm happy to desolder one and send it your way if you don't want to tackle the desoldering yourself.
Alternatively the other poster mentioned new ones available for about $6 posted on Ebay, which is a pretty good option too.
Look at the list of supported ICs, I looked into those first and they're hopeless.
I've looked at a few projects out there and this one seems to have the best set of tested ICs (excluding designs relying on even harder to find parts) and the ability to program in new ones. Plus it tells you what part of a chip test failed.
If something like this (or newer):
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popped up cheap, I'd definitely be after it instead.
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