reballing temperatures

[woodford]

hi,

ive had 2 laptops this week that require reballing.on both occasions ive removed a couple of pads from the mainboard when removing the vga chip.

i'm removing the vga chip at around 230c, shall i go hotter than this or is it better to stick to 230c but leave it longer.

thanks.

[skywalker]

Re: reballing temperatures

You don't say in your post what method you are using to remove the chip, are you using flux ?

[woodford]

Re: reballing temperatures

i am using a ersa reflow machine with a air sucker tool.i am also using liquid flux.

[skywalker]

Re: reballing temperatures

Do you have any experience within the reflow industry? Please be honest and I will try and help you out.

[woodford]

Re: reballing temperatures

yes, been fixing laptops for a while including reflowing however the company i work for want to move away from reflowing and concentrate on chip replacement and reballing.ive no problem with the actual reballing process, we just seem to be having difficulty removing the chips without damaging the board.

[skywalker]

Re: reballing temperatures

Could you give me more info on the flux you are using ,There are some excellent liquid fluxes out there but they all have different purposes. I think the problem you are relating to is you are trying to remove the chip to early and or there might not be enough even spread of the flux under the chip for the heat dispensation . Could also be the placement
of the TC on the board are you putting some flux around the TC. There are a number of reasons why this could happen , but we will accomplish this in the end

[woodford]

Re: reballing temperatures

not to sure about the make or type of flux but it was sold to us with the reflow machine from a well known uk supplier for reflowing purposes.we are using quite a lot of flux and making sure it gets under the chip.the thermocouple is right up against the side of the chip and yes there is flux around the end of the thermocouple.

[skywalker]

Re: reballing temperatures

There is a big difference temperature wise whether you are attempting to re-flow the bga rather than remove it. Most lead free solders melting point is 217c , you say your temps are 230c this is a good temp for re flowing the chip
all that you have said should be given good results when removing the chip.
I think you may need to experiment more with your machine , first of all I would try another site close to the chip for the Tc and allow between 1-2mm away from the chip I own a jovy which is very similar in comparison to one of the ersa models , it has taken nearly 12 months for me to get this to perfection and I am still learning something new daily with the machine
Try and nudge the chip very softly with a dental pick to make sure the solder is flowing underneath when its close to 217c before removing it

[woodford]

Re: reballing temperatures

thanks for the help, i'll try again tomorrow and let you know.

[Dgtech]

Re: reballing temperatures

If you could, post the info and model number of the reflow station you are using. This is something I may need to look into. I just need to know the price of something decent for doing this. I can do most surface mount stuff with irons but not the BGA.

I seen this type of soldering done on you tube and I think it's sick. It's madness. LOL

[woodford]

Re: reballing temperatures

i'll post the info tomorrow as i cant remember the exact model number of the reflow machine.i do know it was over £20000 so its not a cheap model although ive used some of the sub £1000 models and to be honest there wasnt that much difference in capability, the only difference i noticed was the poor build quality on the cheaper unit.

[Linkk]

Re: reballing temperatures

I think Skywalker is right, Your temps seem fine for chip removal, any higher will result in popcorning.
What flux are you using ?, Using the right flux is essential for chip removal, I've heard good things about Chip Quick liquid flux so you might want to look into that

[godin]

Re: reballing temperatures

I am currently learning the Jovy and can agree that at 230 you should be easily removing the chip. Are you getting enough heat from the bottom? This was my early issue.

[thesloc]

Re: reballing temperatures

I am currently learning the Jovy and can agree that at 230 you should be easily removing the chip. Are you getting enough heat from the bottom? This was my early issue.

This.

For lead-free removal you need to get up to 150C before turning on the IR beam up to 230C. For a push of about 80C

After you you reball, and I'm assuming you will use leaded components, then the bottom heater only needs 100C since the liqueous (melting) point of Sn63Pb37 is about 183C. For a push of about 80C.

Also, don't use liquid flux. It is highly volatile under extreme temperatures and is easily affected by humidity. This is what's likely causing lifted pads.

For BGA rework, I would consider flux paste. Amtech 559 ASM.

[godin]

Re: reballing temperatures

Thanks for that. Yes I am really pushing the heat from the bottom and only lowering the top heater at 185 degC for the last push up to 230.
Interesting what you say about liquid flux. I did start using it for a bit and was finding that I was getting solder resist damage when I was cleaning the pads on the board. I stopped using the liquid and no more board damage. I suspect the 2 are related but not sure.

[thesloc]

Re: reballing temperatures

Yeah, don't fall for that "No Clean" flux shit. It's horrible.
One time I used it and I could even hear popping sounds.

[godin]

Re: reballing temperatures

This wasn't no clean but did crackle and pop big time

[thesloc]

Re: reballing temperatures

Yep. Stay away from liquid fluxes.

eBay sells Amtech, that's the best flux for reballing. Seriously.

[mattbrad2]

Re: reballing temperatures

If using an IR rework station, please stay away from the no clean liquid flux. It's extremely volatile when its essentially being microwaved. I've found it to be quite good however with hot air. Tends to reach its activation point very quickly. The resulting solder balls under liquidus are very bright and shiny. Amtech is good stuff when its genuine and not the knock off stuff (you'll know easily by the smell). A great alternative is Chipquik smd291.

[aqibi2000]

Re: reballing temperatures

This is entirely wrong. If you have ever used Kester liquid flux you would not have state this. I have been reballing for several months with no issues with liquid flux, the noise is merely the flux activation.