I purchased some of the PSoC4 $1 chips in the SSOP package... when received they were nicely packaged and sealed in a single moisture proof bag with probably a desicant... and a warning about using within 168 hrs after opening, etc...
My question is what kind of problems or issues arise if the chips do get exposed above the limts mentioned..??
Are they moslty related to production reflow and such?
I plan to hand solder these onto Schmartboards as need for projects, but I won't be using my entire batch at one time.. using only one or two at a time then storing the balance for future use, etc.. Will I experience solder problems down the line in time with the exposed chips?
Any tips on storing unused chips once you open the bag..??
The answer is "avoid corrosion". Humidity and oxigen both from the environmental air allow corrosion of the solder-pads of the housing. The same applies to your PCB, but here the pads are often gold-covered to hinder that. Corroded solder pads may refuse to solder but at least use more flux.
So best would be to store the remaining chips in a (the original) bag together with some silica gel and as few air as possible. Seal the bag.
The PSoC4 chips (I'm looking at the CY8C4125AXI-483 as an example) are specified with MSL3. That means they have a 'shelf life' of 168 hours. After that you would need to 'bake' them - look at the JEDEC specification for that.
But if you do hand-soldering only, and take care not to heat the chips up too much, this most likely is no problem. You can also re-seal the bags after you took one of the chips out - just keep the humidity indicator card and the desiccant in there and close it properly. I use sticky tape / duct tape to close the bag completely, after removing most of the air.
The main problem is air moisture absortion that can cause cracks in the IC when suddently heated.
This picture explains it better
This is a major concern while reflow soldering, but even then if shell life has been reached you can always bake the chips in an oven so allow slow evaporation.
But, as said before, if soldering with a temperature controlled soldering station you won't likely encounter this problem. Just make sure to reseal the bag everytime you take a new chip out and keep the dessicant in the bag (a a fe wmore if you need to)