[Premium-Rx] Re: SMT parts recovery

[Ed Tanton]

Hi Jan... here is my two cents-or so-on SMTs-how to get 'em... and how to 
store 'em. I had thought about writing this (especially the organization 
part) for some publication, but considering this pretty well covers it... 
and there'd only be some photos in addition... it isn't long enough to 
really matter-so here it is, minus the photos of course.

SMT Parts Recovery. Well, for starters, if they change color, you're dead. 
But consider this... I have just gone through a decision process concerning 
my SMT stuff. Here are my findings:

         1) They're cheaper to buy than troubleshoot. The bulk of the SMT 
parts I have removed with both an EDSYN Hot-Air SMT station and my Princess 
heat gun were discolored at one end-if not both... and I WAS careful. You 
can check the resistors... but you have no idea about internal capacitor 
damage-much less the ICs.

         2) I bought half-a-shoebox FULL of SMT "floor-sweepings". True, I 
got a deal on them. They boil down to the parts that, one way or another, 
fell/dropped/whatever out of the automatic placement machines before they 
could be soldered. I certainly got my money's worth, since many of the 
parts are obviously ok, unused, and wouldn't have been damaged by ordinary 
"floor-sweep-handling". The tantalum capacitors were especially cost effective.

But what about the ICs. Hm-m-m. There were about 5 or 6 (specifically-for 
some reason) 20 MHz oscillators. Them I can check if I need to use them. 
The TTL & LS-TTL ICs are very likely OK. BUT... the CMOS ICs... well... I 
dunno. They are a fair amount of trouble to solder into place. They are 
more than a fair amount on trouble to remove. Most of them cost less than 
$0.65 in tens from DIGIKEY or Mouser. Hm-m-m. It AIN'T worth the risk. OP 
AMPs are a maybe. Likely OK... but a lot of trouble to remove when they are 
only $0.45 per part.

CONCLUSIONS:

         1)  Surplus parts are not a bad idea-even by the pound... but 
forget using the CMOS stuff that's not separately tubed or 
non-static-bagged-even then... like a lot of things: you don't know where 
it's been. I figure it has to be 50% less than Digikey (or better) before 
I'm interested. Just as I did for my 20 lbs or so of stainless-steel 
aerospace screws/etc. I got years ago, you can sort parts while listening 
to the bands. Got a LOT of DX that way. It's a decent return on your time & 
trouble investment for difficult-to-damage components.

         2) A MUCH BETTER solution is to buy batches of 10 or 100 when you 
can anticipate a need for specific values; or early on, decide on what 
values you think are most-common, and both watch ebay and order from 
DIGIKEY <http://www.digikey.com/> or Mouser <http://www.mouser.com/>; and 
surplus from the Electronic Goldmine <http://www.goldmine-elec.com/> and 
Dans <http://www.fix.net/~jparker/dans.html>. One warning about surplus SMT 
stuff: most of the SMT prices-especially the ICs-are about THE SAME AS what 
you can get them for NEW at DIGIKEY or Mouser. Also "BaggyBob" 
<http://www.qsl.net/mnqrp/baggy.txt> has very good SMT prices.

         3) I am unwilling to risk the possibility of putting a damaged 
(heat OR static) IC into a circuit. It is difficult enough to troubleshoot 
my designs, w/o throwing in a wildcard. I fully understand it is POSSIBLE 
to successfully remove SMT parts... but as far as I am concerned, it is 
simply not worth the combination of time, hassle, and damage-probability. I 
just don't think <parts removal vs heat-damage = ?reliability?> computes 
for me.

Finally, a word about organization. I REALLY gave this a lot of thought. 
First, I tried small, clear, pieces of tubing with appropriate end caps 
(from Small Parts, Inc.) The idea was that I could then put the tubes in 
with my regular, organized, resistor/capacitor/etc. parts bins. I hated it. 
First, it got in the way every time I was looking for a regular resistor. 
Second, it isn't the least bit static-free (the parts actually STICK to the 
tubing from static-cling.)

My solution for this is an "Aluminum Storage Case" that MicroMark 
<http://www.micromark.com/> sells. Part numbers 14245 (24 containers) and 
81366 (20 containers) 
<http://www.dxmarket.com/160341265593423/system/product-page.mhtml?shop=micromark&code=14245>. 
The "containers" are small aluminum 'cups' about an inch in diameter, with 
clear lid-inserts. Both are $12.95. I label them with the values. My 
resistors and capacitors are in the smaller-sized 14245 (6.375 x 4.375 x 
.75 inches). Since there are several resistor values where I got a roll of 
5000 on ebay, for about $10 shipped, there are some values where I filled 
more than 1 little container, and added a second or third. This has only 
been done for values I 'like' due to the statistical probability of their 
being in almost any circuit (470, 1k2. 4k7; 10k0 etc.) The 81366 is 
marginally larger at 6.5 x 5.25 x .75 inches; and since it has fewer 
containers to boot (20 vs 24), its containers are larger.

So far this has handled things very nicely. I have a Brother P-Touch 
Labeller, and use it for the IDs. As an SMT storage method, it is 
expandable; it puts all my SMT stuff in a small area; and that 'stuff' is 
sufficiently organized and identified, that-for the parts I have-I can 
check immediately to see if I have one w/o resorting to magnifiers. Slowly, 
as I order stuff from Digikey, I order some of the things I think I need. I 
just got a bunch of 555s (surplus ~ $0.25 each) some Digikey 74AHCT00's and 
'74s in the 14pin ISOP package (I think it was.) DO NOT GET *** SSOP *** 
packages... I managed to get the wrong part number and now have 10 4049s in 
the 1/2 mil-pin-spacing I have no protoboards for. It was 'only' $5.00-so 
it's not the end of the world... and there WAS a lesson learned!)

* I just now did a search on "baggybob" and lo-and-behold he has a website 
(now). I haven't looked through the list yet, but he has always had GREAT 
SMT prices.



73 Ed Tanton N4XY <n4xy at earthlink.net>

Ed Tanton N4XY
189 Pioneer Trail
Marietta, GA 30068-3466

website: http://www.n4xy.com

All emails <IN> & <OUT> checked by
Norton AntiVirus with AutoProtect

LM: ARRL QCWA AMSAT & INDEXA;
SEDXC NCDXA GACW QRP-ARCI
OK-QRP QRP-L #758 K2 (FT) #00057