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Topic: breakout board soldering questions (Read 173 times) previous topic - next topic

bgood1130

May 17, 2020, 03:55 pm Last Edit: May 17, 2020, 03:58 pm by bgood1130
Hello everyone,

I am attempting to solder a msop-10 high voltage digipot to a breakout board. This is my first time trying to solder such a small package.

I am using the smallest tip I have, which is the smallest one in this set: tips, and also using .3mm soldering wire

Here is the datasheet to the digipot: datasheet, page 10 shows the pinout out fhe digipot

I soldered it to the board, and put header pins on it as well. After soldering I inspected the leads with a 4x loupe, and I have very good eyes, and do not believe that any of the leads got bridged with solder.

To verify this I decided to check across leads for conductivity by seeing if an led would light up when run through adjacent leads in my breadboard. The led will light up across leads 3 and 4, 8 and 9, 9 and 10, and obviously 8 and 10.

I am fairly certain of my visual inspection, but the results contradict my inspection.

Another possibility I am wondering about is if I should be getting these results across those pins. For instance, 3 and 4 are vss and digital ground. I wouldnt be too surprised if they were internally joined, but I don't believe that to be the case. 8, 9, and 10 I really do not believe that would be the case, as they are sdo, vdd, and w.

Another thing I wonder about is if I may have overheated the digipot leads and shorted something internally.

I believe I probably bridged a lead somewhere, but wanted to get a second opinion on the other possibilities before going nuts.

If the problem is indeed that I am not good enough to solder such a tiny package, would someone happen to be able to point me to another 8 bit digipot that uses i2c or spi, and is good for atleast +24v and is available in a larger package? I have not been able to find anything in a larger package.

Any insight into my situation is greatly appreciated, Thank you.

Byron

MarkT

More flux, less solder.  Seriously try solder wick and remove as much solder as you can, sprinkle on
some rosin dust or a dab of liquid rosin and re-heat the pins.  Flux gives solder surface tension which
acts to separate pins, provided there isn't too much solder.  Any convex surface on a solder joint means
too much solder, all surfaces should be concave.

Testing with an LED could mean you have too much voltage to safely test an unpowered circuit.  Use
a multimeter in resistance mode, most use 200mV full scale on the ADC, so will not over-voltage any
parts under test.

I get reliable results with oven and solder paste and stencil, its so much easier.  You really need
solder-mask on the pcb for fine pitch parts, that really helps, but most break-out boards are professionally
made and quite good for this.

A hot-air rework station is another possibility for small jobs, and allows you to have several goes.  Ceramic
tipped tweezers are very useful to have if you do this.
[ I DO NOT respond to personal messages, I WILL delete them unread, use the forum please ]

bgood1130

Thanks for your advice.

I have honestly never even used flux. I do have some paste flux around for tip cleaning, and already have some desoldering wick on the way already, as I figured I was going to need it. Must I get liquid flux or rosin dust, or will the paste flux work?

My next question is if when applying flux it must only be on the pad, or is it acceptable for some of it to end up on the mask? Will it still make the flux stick only to the lead/pad even if there is some flux on the mask?

As you may have guessed, I have also never dealt with solder paste and stencil. After a moment of looking them up I assume that you use the stencil to apply the paste without bridging pads, remove the stencil, install the ic on the breakout board, set the oven high enough to melt the solder paste, and then put it in the oven for "x" amount of time, and viola!?

Thanks again for your help

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