View Full Version : SRF05 gets really really hot?

10-20-2008, 05:36 PM
My Srf05 worked just fine, but then one of the header pins broke off and so I desoldered all 5, then soldered on a new 5, So my question is, can excess solder or just a small buildup, or flux around the terminal cause it to heat up? Has anyone else had this problem? here are pictures:



When I use a continuity tester, and touch one end to the solder, and the other to a header pin, the circuit completes, so there is no faulty solder

Any suggestions

BTW: The Srf05 does not work at all, as well as heating up very fast

10-20-2008, 08:57 PM
You have a short somewhere which is causing your problems. I would check to see if there is a bridge between pins or if the silkscreen has been damaged from the heat of the iron. Flux would not be a problem.

The other thing could be there is a solder bridge on the other side where the pins are.

Check continunity on the + and -
If your data lines where touching your sfr wouldnt work but it wouldnt get hot.


10-21-2008, 05:40 AM
I checked the + and - terminals, and there is a complete circuit, is the board ruined? What do I do?

10-21-2008, 01:43 PM
It dosnt mean that ist ruined. I would try to unsolder the pins on at a time. Clip the black plastic with wire cutters and unsolder one pin at at a time. You dont want to heat up the board more than you need to. Be careful to not scratch the silkscreen with the wire cutter either.

Clean up the extra solder and post new pictures of front and back but zoom in closer to show a little more detail.

It might be ok still.


10-21-2008, 01:57 PM
Where is the heat coming from on the board? You might want to double check your cable to make triple sure that +v and ground are on the right places on the board.

10-21-2008, 02:04 PM
With the discoloration on that board where you inserted the new pins it looks like you have had some serious heat there, it sounds like you have a short somewhere, most likely cause of your heat build up, shorting to GND. Use the 5 sec rule, My rule is a 25w iron no more than 5 sec and a 40w iron [only for header pins and not components] is 3 seconds.

10-21-2008, 02:15 PM
Multi-layer boards don't generally handle too much heat that well, the via's could be damaged and delamination of the board may have occured causing an internal short, which would indeed mean your board is fried.

It's impossible to tell at a distance though, so take it one step at a time and see what you can come up with.

As indicated above, don't use too much heat, desolder the pins gently.
Given that it's a multi-layer board with via's this may be a bit hard, but you can preheat your board in the kitchen oven, set it at 150C or so and put the board in for 10-15 mins before desoldering. (carefull though, it'll be hot!)

Once the pins are removed, measure each pin relative to ground to check for shorts.

Flux shouldn't be a problem, you can clean it up with a little nail-polish remover though that's a little on the agressive side.

10-21-2008, 02:48 PM
ScuD: Old toothbrush and a little bit of Dawn dishwashing liquid. ;)

10-21-2008, 03:06 PM
Can I substitute for the Belgian kind of dishwashing fluid? :confused:

I use fluxcleaner since I have heaps of cans at work, but it's a mighty good tip that is!
Thanks Lynn!

/edit, one thing I forgot to ask : did you use lead-free solder? mixing lead-free and leaded solder can cause a variety of nasty problems, but using lead-free on lead-free has it's quirks too - tin whiskers being the most common. Although I doubt that's the problem here (they mostly act as a fuse and wouldn't last long enough to cause heating) cleaning the board as per Lynn's instructions might help

10-21-2008, 04:36 PM
Dawn is my fav because it really does cut grease and is "gentle on the hands". Being gentle on the hands means it's also gentle on the components. Cutting grease is good because that's the carrier for the flux. Just rinse the boards well afterwards to get rid of residue.

Honestly - after I scrub 'em with a little 50/50 Dawn and water with an old soft toothbrush, I toss my printed boards in the dishwasher after running a few cycles to clean out any detergent that's left in it. No dry cycle, gentle, no heat. I figure a dishwasher doesn't look or function all that different from the board washers I've used commercially. I just clip the boards up to dry naturally after washing...

I can't promise this isn't harmful, but I've never seen anything bad happen from it in the last twenty something years...

10-21-2008, 04:42 PM
Where is the heat coming from on the board? You might want to double check your cable to make triple sure that +v and ground are on the right places on the board.
The heat is coming from the larger chip on the back I believe