Can a BIOS chip survive hot-air soldering but still lose functionality?

[majster-pl]

Hello everyone,
I’ve run into an issue after working with a laptop BIOS chip and wanted to get some advice.

I desoldered the BIOS chip using hot air and then read its contents with a CH341 programmer (only a read, no write or erase was done). The .bin file was not modified at all. After soldering the chip back, the laptop now no longer powers on.

For clarity:

No surrounding components were touched during the process.

All pads were checked with test points and were confirmed OK.

My question is:

Is it possible that the chip was damaged by the hot-air process in such a way that it still allows a successful read in the programmer but doesn’t work correctly on the motherboard?

Has anyone seen failure modes like this (e.g., weakened pins, internal damage, heat stress, etc.)?

What precautions or recommended temperature ranges do you suggest for safely removing and resoldering these chips?

Any advice or shared experience would be greatly appreciated.

Thanks in advance!

[mon2]

Post a clear pic of the area of this rework. Suspecting that you are missing a connection of SMD resistor nearby.

[majster-pl]

Don't have microphone sorry this is best I have.

[majster-pl]

Those are the images of this are before any soldering was done.

[rumpumpel1]

When soldering with hot air, please note the following: when desoldering, the chip has a good thermally conductive connection to the mainboard. Chip and mainboard have almost the same temperature. You can easily recognize the melting point by the fact that the chip can be lifted off. There is only a small risk of damaging the chip.
When soldering, on the other hand, the chip initially has no thermally conductive connection to the mainboard and the hot air primarily heats the chip and only secondarily the mainboard. When the mainboard has reached the melting temperature, the chip has a significantly higher temperature and the risk of damaging it is greater. It is therefore also advisable to use a bottom heat when soldering.

[majster-pl]

Thank you rumpumpel1 for your clarification, it makes complete sense what you've just said. My next step is to program new chips and try to solder them on using iron solder not hot air this time. I'm also waiting for microscope which I'll use to inspect this area better and take better pictures.

[m1ch43lzm]

Full context https://www.badcaps.net/forum/troubl...12#post3719912

Start at post 117, the BiOS was read correctly, i managed to decode the password for majster-pl but something went wrong when soldering the chip back and laptop doesn't turn on anymore

From the BIOS request thread

Check that, unfortunately it looks ok... I have picture form before and after - the both looks the same.
It looks like I've accidentally damaged something else on the board 😥
When I connect charger the IC is getting hot (checked with thermal camera) not sure if anything else can be done.

Maybe too much heat/time when soldering? Also you have to let the chip cool down before applying power

For those chips I prefer to add leaded 63/37 solder to the pins when desoldering with hot air, and solder with the soldering iron

You can use W25Q64JV and W25Q128JV as replacements, those are listed on the LA-K051P schematics

https://www.badcaps.net/forum/troubl...view-schematic

[majster-pl]

Thank you m1ch43lzm I'm warning for new chips to be delivered. Once I have them I'll attempt to program and replace. Also in next few days should have better microscope to inspect the area.

[majster-pl]

I have few better quality pictures, the component around doesn't look misplaced BUT they look like they might of seen better days (probably burnt) a specially the one by DO (pin 2) by one of the bios near "UC12" painted on the board, it almost look like its cracked in the middle.

How do I check if this can be a fault and If this is faulty how would I find what this should be replaced with?

Thank you in advance.

[majster-pl]

I've managed to get schematics for this motherboard and now I'll know what to replace those with if needed.
2x Bios schematics attached.

[m1ch43lzm]

Measure those resistors, should be close to the values listed in the schematics (linked above)

[majster-pl]

Tested and sadly they all have values as expected... Iast chance is to program new bios chips when finally arrives and see if that will fix the problem....
Thanks for your help!

[ianbak]

This is why I prefer to use a clip to extract the data rather than to desolder the IC! The ones that you get typically with a CH341 are rubbish, but the ones with spring-loaded needles that you can get quite cheaply on AliExpress work for me everytime! The only challenge is that you have to hold it in place with one hand whilst controlling your programmer software just with the other!

[majster-pl]

ianbak yeah this is what I've tried initially but I think the components around were drawing power and it wasn't detecting the chip. This is why I've made decisions to desolder it.