Electronic – How would a chip socket affect the chip

socket

I have a little habit of socketing all DIP chips used in my circuit (so at least if the design failed I can recycle the chips easily). Now since I am trying my hands at multimeter DIY'ing (with a all through-hole construction hence all the DIP chips) I am seriously considering side effects of placing chips in sockets.

The chipset include the ICL7135 4.5-digit ADC. On the digital side there are CD4511B/ULN2003 LED display driver chipset and a pair of GAL16V8s implementing the autoranging logic (without those there would be a few more 4000-series CMOS chips.) On the analog side there are the AD736 RMS-to-DC converter, REF03 voltage reference and a few op amps (TLC227x and OPx177 primarily.) There is also a power supply section with two MC34063s.

I think socketing digital chips, MC34063s as well as the primary ADC won't hurt (especially the GALs which required programming) but what about the analog chips? Will socketing those chips bite me? (If I can socket the REF03 maybe I can individual test and label them before plugging them into the PCB)

Best Answer

So what are some things that adding a socket for a TTH DIP part actually does, circuit wise?

  • It adds a bit of wire length to your traces (all equally)
  • It adds a bit of resistance (mΩ at most, unless corroded), which depending on the socket quality changes more or less over time
  • It adds a tiny bit of inductance and capacitance to your traces
  • It adds more space where dirt can accumulate and form GΩish resistance paths

Mechanically it does

  • add the possibility of your ICs falling out due to extreme vibration or temperature cycling or PCB flexing
  • reduce the possibility of damaging the IC due to PCB flexing

So what you have to do is to think if these are a problem for your design, which we can not really do, since we have no idea about your design. But since you are using TTH parts and with a bit of guessing, what we can tell already is:

  • Your bandwidth requirements are far below the case where length and inductance makes a difference
  • The tiny changes in resistance will likely be much lower than the tolerances of the parts you are using already

The mechanical parts are up to your liking, and then whats only left is the dirt that can accumulate, which is also preventable in other ways.

So all in all, we can say that its pretty safe. Actually if you look at quite some older good multimeter teardowns on youtube et. al. you will see that there are quite some ICs that are socket by people who know how to design even 6-7 digit multimeters.

TL;DR

You should be fine with socketing.