Temperature for removing ROM chips

[slingshot]

What's a good temperature to use (for the hot air machine) for getting the ROM chips off the PCB's ? Obviously without nuking them etc ?

 

[LarrySabo]

I preheat the PCB to 215C then use hot air at 350C (focused on thePCB/legs, not the top of the ROM), and flux of course.

 

[Jared]

That works for newer drives, but the old ones require a higher temperature. I usually keep my gun set from 450C to 480C at a very low airflow. I'm of the mentality that it's better to use hotter air for less time than cooler air for longer.

 

[Square]

That works for newer drives, but the old ones require a higher temperature. I usually keep my gun set from 450C to 480C at a very low airflow. I'm of the mentality that it's better to use hotter air for less time than cooler air for longer.

Why at a low airflow? Wouldn't it take longer?

Sent from my Z828TL using Tapatalk

 

[Jared]

Why at a low airflow? Wouldn't it take longer?

The reason for the low airflow is to avoid blowing resistors and other small components off the PCB while you're doing it. Using a low airflow and putting the gun nice and close to the PCB concentrates the heat on just the component you're trying to remove with minimal impact on the rest of the board. This is especially important with boards such as the WD 800022-000 boards which are easily ruined by overheating since the main IC is right near the ROM chip.

 

[slingshot]

I can't use a pre heater for the PCB as I don't have one and Im struggling with the straight nozzle on the machine, so Ive ordered an angled nozzle instead. Need to calibrate the temperatures as well as I don't think its chucking 400 degrees out the end like the display says :roll:

 

[pclab]

The best thing I think is to do as I did:

Practice in several PCB's the best temperature until you find it without damaging the ROM.
When you find it, you already know the parameters.

 

[slingshot]

Im doing it under a magnifier lamp as I can't see it properly :lol: so getting the air nozzle in whilst its straight up has been really awkward.
Once my new bits arrive I will continue practicing
Thanks guys

 

[LarrySabo]

I second pclab's advice. Also, don't rush it by using too high a temp, lest you kill the ROM. You might wish to get some ChipQuik low-temp solder alloy (bismuth) and use that to lower the melting temp of the native lead-free solder. After using ChipQuik, be sure to fully remove any ChipQuik residue and clean the pads before resoldering with regular solder.

 

[slingshot]

I second pclab's advice. Also, don't rush it by using too high a temp, lest you kill the ROM. You might wish to get some ChipQuik low-temp solder alloy (bismuth) and use that to lower the melting temp of the native lead-free solder. After using ChipQuik, be sure to fully remove any ChipQuik residue and clean the pads before resoldering with regular solder.

Thanks Larry, I will get some this week and do some experimenting