solder

Feb 06, 2009 17 Replies

I'm working on small project using some prototype circuit boards (8mil traces with 8mil gaps, no solder mask, mostly through-hole) and had a little difficulty with the soldering. Maybe my eyesight isn't as good as it used to be, or maybe the tip on my soldering iron is a bit worn out (it's a good temperate-controlled fine-tip soldering iron, but almost two decades old), or maybe it's the solder itself.



Anyhow, I was using 0.031 solder for this job. I'm wondering if that's typical, or if I should find something finer? Where should I shop? I'm surprised to see solder is now very expensive via mail order ($20-$60 per spool?).



Also, I had a bit of trouble with the solder riding up on the tip, rather than onto the pin and pad. Yes, I did make sure to heat the pin and pad, and apply the solder to the joint.



Thankfully I didn't bridge any of these microscopically-small 8mil gaps, but it was a bit of a slow and tedious process.


Pick up an Optivisor. It really helps.

Might look at the pads, too. (no pun intended) If you're using round pads, try switching to elliptical pads for more contact area with the iron's tip.

0.031" should be just fine for through hole (and much surface mount stuff). 63/37 or 60/40?

Try fluxing the joint just a little before applying the iron. Kester paste flux (the kind in the flat little tubs) is fine; you can dab some flux on the joint with a toothpick. Or splurge and get a syringe of liquid flux. I prefer "regular" (not no-cleanup) but YMMV.

Rich Webb Norfolk, VA

is it the IC that you are trying to soldering on to the board?

from my experience i would suggest using solder paste and heat gun. using toothpick to apply small amount of paste on top of pads, use the heat gun to melt it, they will become hard solder and stick with the metal pad. then clean the rest of the paste off. place your IC on top of the pads, pins above the solder that's already there. carefully use tweezer to hold it there. then use the heat gun again, once the solder melted, the IC will drop on to the pad perfectly.

it require some practice, but i find this is the best way of solder small foot print ICs, instead of solder each pin at a time..... beware of the heat gun, especially if you haven't use one before, if not careful you can burn the board or melt some other parts close by.

hope it helps.

Ren

Hi, Is the solder you purchased new? It might be RoHS solder, it contains no lead and needs a higher temperature. It also doesn't wet as well.

http://www.hmcelectronics.com/cgi-bin/scripts/product/4800-0039/ JF

Well, that doesn't have quite the primitive ambience as does a hunk of resinous goo on the end of a wooden stick but... probably a lot more practical. ;-)

Rich Webb Norfolk, VA

You want primitive? Try a lump of real Rosin, straight from a third world market stall, beaten to a powder and a shot glass of the local clear unsweetened distilled rotgut to moisten the toothpick . . . . If the rotgut is over 90% alcohol, you can dissolve the rosin powder in it and use a brush!

Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED) ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk [at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL:

The flux that comes in a package like a Sharpie/Magic Marker is nice for SMT parts.

You don't say what brand solder you're using. There are brands of solder which use very poor grade fluxes, Globe being the worst I've ever seen. Quality of flux in the solder makes a big difference. I prefer Multicore or Kester 60/40 or 63/37, good old RMA flux, around

0.020 to 0.025" diameter for most through hole. Your 0.031 dia solder should be OK. The newer no-clean fluxes are OK if parts are clean, but not as good as RMA.

Solder riding up on the tip means that your tip is dirty. The tip is so dirty, it's solder repelant and needs to be scraped clean. Multicore makes a tip cleaner with pumice in it which cleans, tins, and fluxes the tip. The old, and unavailable except through E-Bay, TTC-1 tip cleaner is really good. They have a newer version out which is lead-free and works OK. This usually gets tips working like new. If tip cleaner doesn't work, you need a new tip.

If all else fails, use liquid flux. Again, I like RMA. Your joints will come out looking very pretty with good flow. You can use alcohol to clean the board, but it will usually leave behind some residue unless you wash it a couple times then do a quick final rinse in running hot water.

Newark is a good source for soldering supplies. Digi-Key and Mouser's lines are too limited these days.

Mark

If those are just bare copper (not HASL or otherwise plated) then you will need to flux the pads before you get nice flow on them like you might be used to with more finished PC boards.

Ben Jackson AD7GD http://www.ben.com/

8 mil is fairly wide, but if there are a number of them side-by-side with 8 mil spacing AND you need to solder to *just* one, then things can get a bit dicey. Solder bridging is not too much a problem except when you try to NOT bridge the traces; likewise it is impossible to bridge them when that is exactly what you want...

As far as solder goes, i could send you some Ersin Multicore 0.023

60/40 and/or Kester 0.025 96.3/3.7 lead free. All i would need is your address; is that expensive enough?

Yea; so-called "no-clean" is bitchy; go glazed - donut use the stuff.

Balderdash. Silver bearing solder has a (slightly) higher MP that has little effect when using standard hand soldering irons. And it wets a lot better, and a good solder joint has a rather nice mirror-like finish that is impossible to duplicate with tin-lead solders.

Liquid flux like that is the new magic, compariable to that white stuff used in body work (Senior moment - forgot name).

0.71mm seems to be the smallest common solder size. (I figure that's 28 mils)

at that price it sounds like you're talking 1kg (2.2Lb) spools. OTOH there may not be much demand for finer solder. (jaycar.com will send you a 1kg spool of 0.71mm solder for 30 bucks inc. surface postage)

0.56mm solder is less common and more expensive.

try a flux pen.

why no solder mask?

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surface postage)

Very Low cost hot air reflow/rework gun and and paste dispensing available from China complete kit built up for =A3200 I also use 150C hotplate for single sided. Results quite professional

I was using .015" multicore 'rework' solder about ten years ago. We had no trouble finding it.

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