Testing solder joints

[linuxworks]

Quote:

Originally Posted by Uncle Erik /img/forum/go_quote.gif When working a PCB, I solder the leads in, clip the leads, then spend a second to reflow the joint. That's how you get smooth pads after clipping leads and the reflow pretty much guarantees against a cold joint.

lately, I've been doing that, too.

initial solder (I do one lead), then I check the component to get it against the board 'looking right' and solder the other lead in. then go back and do a better job on the first. then clip leads and then retouch (maybe using flux) a final time. it gives a good guarantee and a good look. but its extra work.

 

[zkool448]

Like scompton, i'm about to do attempt my first pcb (SOHA II) as soon as the parts arrive... what's the best way to keep the components 'flat' on the board while soldering the leads? I'm guaranteed to burn a finger or two if i try to hold them down with bare fingers underneath

Some mentioned using tape, we have plenty of hockey tape in Canada

Are there any other techniques used other than tape others use to accomplish parts sit nicely on the board? thanks.

zk

 

[linuxworks]

I use fingers. it teaches you to NOT dwell too long on the joint (lol)

(no wisecracks, ok?)

 

[SiBurning]

Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif I use fingers. it teaches you to NOT dwell too long on the joint (lol) (no wisecracks, ok?)

That's okay, but it can get expensive to clean up using a good quality fingerprint removal solvent.

 

[tomb]

Quote:

Originally Posted by zkool448 /img/forum/go_quote.gif Like scompton, i'm about to do attempt my first pcb (SOHA II) as soon as the parts arrive... what's the best way to keep the components 'flat' on the board while soldering the leads? I'm guaranteed to burn a finger or two if i try to hold them down with bare fingers underneath Some mentioned using tape, we have plenty of hockey tape in Canada Are there any other techniques used other than tape others use to accomplish parts sit nicely on the board? thanks. zk

Tape makes a mess, doesn't stick well once you've got some flux on the board, and it doesn't have the pressing force needed, IMHO.

I build every PCB on a flat wood board (actually a foot long piece of 1 x 12, finished white pine). The standard technique is to solder one lead, while holding the iron and keeping the solder melted, gently mash down so that the part is pushed flush against the top surface of the board from below. After soldering/mashing that first lead, flip the board to check that the part is flush and hasn't turned slightly. Flip it over again, and the second lead is then a snap to solder in place, and your part is nice and flush against the board - and straight. Check as you go along for other parts. It works very well as long as you keep track of the parts height. You can solder the entire set of resistors for a PCB in one sitting, for instance - soldering all the first leads, flipping the board over and checking, then flipping the board over again and soldering all the second leads. (Note: the leads are bent before soldering. It won't hold the resistors as tight as desired, but it'll keep them from falling out as you flip the board over and again.) Things can go very fast this way if you're organized.

 

[keyid]

I like to bend the leads once through the holde to make sure they are making proper contact to the ring. This also secures the part to the board as you turn it upside down. Once it makes proper contact solder is just a way of securing it. Use flux.

 

[MACDRU]

The 2 best things I found that are useful are good solder and great soldering iron. I use a good quality Weller 25w soldering iron with a t6 tip. Cost me about $40 with two extra tips. Always use Cardas quad eutectic solder. Has a melting point of 375F.

 

[bhjazz]

Quote:

Originally Posted by scompton /img/forum/go_quote.gif but there is a big ball of solder on the front of the board. Almost as big around as the resistor.

You might consider getting some Quick Braid or other copper-based braid (or a solder sucker). The braids do take a bit of practice to work their best, but they can clear out that extra solder. Remember when using them to: tin the iron, apply braid to subject-to-be-removed solder, then apply the iron to the other side of the braid (it's flat). Wait a second and...slurrrrp...You'll feel the solder "lump" soften and get picked up by the braid.
Remove heat quickly.
Pat self on back.
Take a nice, big swallow of a choice beverage.

 

[zkool448]

The entire process is like an art, should take a lot of practice and experience before one can perfect it.

From what I've gathered so far:
a) use decent iron with correct temp setting, flux and high quality solder recommended
b) place leads through holes, then bend making sure proper contact to ring
c) solder one lead only, While solder still melted mash down to flush
d) flip and check to confirm component not turned and positioned correctly
e) flip and solder second lead, then clip leads
f) spend a second to reflow joints to deal with cold solder (ie. don't dwell too long on the joint

)
g) use braid/wick to cleanup excess in case of a mess

Excellent tips and really helpful, thanks guys

zk

 

[zkool448]

...oh, and

- Pat self on back.
- Take a nice, big swallow of a choice beverage.

 

[EFN]

For my case, a MultiMeter with beeper function to check for continuity works. Usually a cold solder joint will beep weaker than a good one.

 

[linuxworks]

Quote:

Originally Posted by SiBurning /img/forum/go_quote.gif That's okay, but it can get expensive to clean up using a good quality fingerprint removal solvent.

hey, if I could remove my fingerprints, think of all the CRIMES you could commit and get away with!

 

[ILAMtitan]

Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif hey, if I could remove my fingerprints, think of all the CRIMES you could commit and get away with!

You have a soldering iron. Trust me, it will only hurt for a little bit.

For testing joints I find the continuity tester to be the greatest function on a DMM. I probably use it more than anything else on there.

 

[linuxworks]

I don't know if I've ever tested solder joints. I've always ONLY just used 'appearance' as my guide. after you do it a while, you get to know what looks right and what doesn't.

procedure is also important, WHEN you solder. if you have the technique down, you almost don't need to check.

funny analogy: in photo, they call it 'chimping', when you take a shot and then immediately look at the lcd display to see your photo. checking every solder joint might be a form of 'electro-chimping' (LOL!!!)

 

[kuroguy]

not sure if this was mentioned yet...
NEVER use the tip of the iron to melt the solder. That will pretty much guarantee a cold joint.

Always use the iron to heat the lead and ring and melt the solder on the opposite side of the lead from where the iron is placed. That method guarantees that the lead and ring are hot enough to accept the solder.