Electronics help changing a soldered processor

[gregzz4]

I've ordered a new chip for a pcb I'm working on
It's a flash 256MB SRAM chip, and I've never changed one before
I have solder wick
I've been told to 'soak' something with acid before inserting the new chip
I'm assuming this means to soak the pcb in the area where I'll be soldering ?
Input here would be appreciated

I gather I should also be using an anti-static wrist band or similar, and not solder all 28 pins at once to avoid overheating the chip ...

Any other tips ?

[Cal_stir]

If the chip is discrete component (has legs thru the board) you could solder in a chip holder then insert the chip, no chance of overheating.
If surface mount then flux the contact points and solder a few pins at a time, there may be a chip holder available for surface mount as well.
Yes wear anti-static, copper wire around your wrist and grounded will work.

[mike31154]

As Cal stir mentioned, if you can find a socket that will fit the pin configuration, it would be best to solder one of those in there after removing the original chip & then you have a plug & play option for the new chip. Depending on the price of the new RAM chip, you may not wish to risk cooking it while soldering if you have minimal experience soldering delicate electronics. Might be an idea to try the procedure on scrap components first if you have something like that kicking around. If not & you have a burnt out CFL bulb, crack open the base, there's a nice little PCB in there with tiny components you can practice on. Just take care you don't break the bulb & release the mercury (albeit small amount) in there.

What type of soldering iron do you have, is it adjustable & what tip is on it? You'll need a fine tip to avoid overheating adjacent pins & the board while soldering. You should also use a heatsink on the pin you're soldering/de-soldering. There are springloaded clip-on heatsinks available that you can attach to the pin you're soldering between the chip body and the solder joint.

Also make sure you have some flux on hand. This will come in handy for de-soldering. Put some flux on to the wick and it will help draw the solder up into it. I would recommend getting a 'solder sucker'. This is a small spring loaded plunger type tool that you can activate with one hand while applying heat to the solder joint with the iron in the other hand. It will suck the solder up with the push of a button. This procedure is quicker than using the wick, thus protecting the old chip should you wish to use it elsewhere. Once the old chip is removed, you can use the flux & wick to clean up all the holes for the new component. I don't know anything about an acid bath, I think if you clean up the area with flux & wick, you should be fine. Less hazardous than messing with acid as well, although most flux is corrosive as well, so wipe the area well with a paper towel when done, maybe use a bit of alcohol on the paper towel. Basically what you're doing is removing as much residual flux (corrosive) as possible. I think the acid bath may be the procedure used to actually produce the PCB, that is, dissolve all the copper except for the runs designed to create the circuit on the board.

[gregzz4]

Thanks for the help guys

I'll grab a wrist band today, and see if I can find a finer tip for my iron
It's just plug and play, and the tip is pretty clumsy
I have flux and a solder sucker, but I never liked the tool much

The chip is surface mount, so it'll be a bit fun 'till I get the first few contacts soldered, but at least it'll be easy to remove the old one

I'll see if I can find a heat sink and a chip holder too

I can only hope the new chip solves the problem as the unit is over $100 to replace, but the chip is only $4 :surprise:

[gregzz4]

I just got off the phone with Digi-Key
Amazing service
Customer service put me through to the tech department and we talked for over 10mins. They found me a relay I couldn't find on my own.
All that time for a $2 part
Awesome

Then I was even able to add the extra parts I need to my original order, so I'm still only paying $8 shipping

Gotta love online shopping :smile:

[windcoast reefs]

I just got off the phone with Digi-Key
Amazing service
Customer service put me through to the tech department and we talked for over 10mins. They found me a relay I couldn't find on my own.
All that time for a $2 part
Awesome

Then I was even able to add the extra parts I need to my original order, so I'm still only paying $8 shipping

Gotta love online shopping :smile:

Yeah they really are great! I just had a dc pump driver go on me and they managed to find all the parts I needed to get it running again.