Soldering ICs to the circuit boards?

[grizzvolga]

Hi,  I have an EIII keyboard that I am trying to bring back to life. Many of the sockets in the CPU and micro-controller boards are very rusty and probably failing, so I would like to get rid of the sockets and solder the ICs directly to the boards.

But now comes the question: I have noticed that there seem to be solder lugs not just in the back face of the boards, but also in the front face, right underneath the sockets/ICs. Are this functional solder lugs? Does this mean that IC legs need to be soldered to both the front and the back face? Or do I just need to solder them to the back face like you would do in your average circuit board?

Thank you!

[Emu276]

If you are going to the trouble of removing the old sockets, cleaning the PCB under them, and having to solder new parts in you might as well install high-quality sockets again. Two reasons: 1) the risk of overheating and damaging a socket when soldering is much less worrisome than damaging a hard-to-replace IC and 2) having all the ICs in sockets makes future trouble-shooting and IC replacement much easier. If you install brand new quality sockets, I wouldn't worry about issues of bad IC connections with the board (if that is why you think directly soldering ICs is better).

Again, since you have to clean and re-install parts anyhow, I say just do it the right way that makes future maintenance easier.

Howie

[Freddy]

Agreed, when I work on the EIII, I instead unsolder soldered chips and add a socket to it.

I would never install chips without a socket. What if one of the chips is bad? The chance of damaging something on the way is too big - even for professionals.

[grizzvolga]

Agreed, when I work on the EIII, I instead unsolder soldered chips and add a socket to it.

I would never install chips without a socket. What if one of the chips is bad? The chance of damaging something on the way is too big - even for professionals.

OK, you are right!  I'll use brand new sockets!

But back to my original question: Should I solder the sockets only to the back of the circuit board, and pray that the solder lugs at the back are somehow connected to the solder lugs at the front, the ones underneath the sockets? Or do I need to also apply solder paste to the solder lugs at the front of the board?

Thanks!

[Freddy]

I'm 99,99% sure that both sides of the solder lugs are connected. If you are unsure, just measure it with your multimeter

However, only unsolder components if you really know how to (de)solder. Ripping out a single solder lug from a multilayer PCB can ruin the entire board. Definitely use the destructive approach by clipping of each leg from the chip in question before unsoldering the individual legs.

Just read your initial post again. Definitely a really bad idea to replace the sockets if there is is no need to do it. Just clean them, remove the corrosion and apply some contact spray.