DIY : tsnm (Touch Sensing Note Memory) by Doboz


#41

So i finally got everything together, sorted and ready to go. The very first thing I did was solder the 16pin IC chip… upside down. 3mins to make that mistake and hours after trying to remove the chip. No luck on that. :exploding_head:

Super suck town.


#42

Get some Chip Quik! Makes desoldering surface-mount components easy and safe.


#43

I’ll look that up for next time, thanks. :slight_smile:

Honestly, after almost 3 hours of solder wicking it with no luck, i just ripped it in half with plyers. Better the chip/board than my own hair i suppose. Its going to be a while before I can mentally revisit this project without wanting to immediately smash it with a hammer. :nauseated_face:


#44

Uuh I know this feeling. My first smd project (clouds) ended in the trash. I destroyed some traces on the pcb trying to desolder a wrong orientated IC… but don‘t worry. It gets better with every component you solder (or desolder :joy:)!


#45

so the trick to removing chips you’re OK with destroying is:

  • take a pair of right angle cutters and snip the legs from the body at the body.
  • the IC body should fall free
  • now just heat up the pads and the remaining legs will fall off.

this minimises chances of destroying pads. It’s the sort of thing I do with, say, op-amps, but wouldn’t do with an expensive DAC or what have you.

I just put a CEM3340 upside down, and that’s a £6 part, so wasn’t going to destroy it; I had fine success removing it with a hot air gun. Really, for SMD removal, hot air is the way to go, and you can find cheap hot air stations on ebay for £30 or so.


#46

Did i do it again? I think i am making some wrong assumptions about what way is what…

Are these upside down?


#47

I’m sorry to say that: yes… :frowning:


#48

Oh thats awesome haha — so i had it right the first time!
I’l going to go sacrifice some small fluffy animals.


#49

If you’re happy to destroy the chip, my approach is to put a massive blob of solder across both sets of legs. then jump the iron back-and-forth between the blobs on either side, and the whole chip will slide away. you’ll need to solderwick your mess afterward.
^^ this is not advisable with a chip bigger than say 32pins.

edit: if you’re quick about this approach, you can wick the solder blob off the chip (after it’s removed) and reuse it.


#50

Thanks @Galapagoose – I gave that a try one time and I could not get it work hahah, I’ll try it again sometime though, I obviously need more practice. :slight_smile:

I ordered some of that chip quik stuff, and I’ll give it a go (and report back). If that doesn’t go as planned, i’ll probably try to snip the legs and then remove the pins one at a time and start again.

The mistake I made was that the first chip I put on (just by chance) happened to have a horizontal line printed on one side, and I immediately thought that that line should match up with the printed line on the pcb. But I see now that the other marking (line+semiCircle) on the PCB markings is showing where the first pin should be, not the clean line. :thinking:

I noticed that the resisters (and some of the ‘C’ parts) have no markings on the PCB for orientation. Does that mean that any way goes, or is there a specific way they should go on?


#51

I ordered a couple of the 4u version from the next batch for my fledgling Serge system. Can’t wait! Also have to practice smt soldering before I attempt these.


#52

Jep. Resistors have no orientation. Capasitors can have one. In case of the tsnm only the through hole electrolyt caps need to be placed the right way. The ceramic caps have no orientation


#53

great … I have a feeling the next solder session may be the last :slight_smile:


#54

The last because the module is built ? :blush:

Or the last session in general?


#55

with a hot air station desoldering chips is freakin easy, you should consider buy one. you can find some cheap chinese ones like the 858 on ebay for 30 eur.


#56

haha because it will be finished!! (knock on wood/cross fingers/ pray to PCB gods)
Thanks for your help – i’m sure i’ll have a couple more questions before its complete… :slight_smile:


#57

checking it out now – thanks for the tip!


#58

good luck!!! received my pcb/panel today!! time to order all parts :heart_eyes:


#59

@reijo ahh cool, have fun!
I used the chipquik and it worked really well!!

After cleaning the pcb, i noticed one spot where it looked like there was a little copper color — i dont think i was working there but just wanted to ask if was a problem:

…and the resused chips, its not pretty but does this ok? :

You can see that copper coloured bit between r10 and r11 again…


#60

Copper-colored bit looks like a hole in the solder mask (the green stuff). Not a problem unless you accidentally connect it to something else (like one of the pins on IC1) with a solder blob.

Glad to hear the Chip Quik worked well.