How to re-flow a BGA chip

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LG Television

Repair guides and support for your LG TV.

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tron @tronz

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发帖于: 2021年7月8日

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How to re-flow a BGA chip

May need to re-flow a BGA chip on a LG TV’s mainboard. I understand that the temperature regimen is the key to success. Therefore, please suggest the best methodology. Please specify all stages for warm up and cool down with temperatures and durations for each. Also, do you believe a heat gun with a thermometer is enough or should I get a relatively inexpensive re-flow station where temperature can be set? Recommendations for liquid flux and thermal paste brands or whatever other advice on topic is greatly appreciated.

I would like to mimic the manufacturing process as closely as possible to get a lasting result, so if it helps, my TV is a 10 year old LG LED TV Model: 55LV5400-UB

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We would at least need some pics of the mainboard and BGA chip.

由 Chris Stables 完成的 2021年7月9日

@imicrosoldering there are two IC's under there. I suppose one is talking about the video processor which is marketed as a LGE35230 but it is a BCM35230kfsbg BGA IC

由 oldturkey03 完成的 2021年7月9日

@imicrosoldering any help and pointers, much apreciated :)

由 tron 完成的 2021年7月9日

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Chris Stables @imicrosoldering

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I wouldn’t try to reflow these chips just yet. What I would suggest is to heat them up at 200 degrees Celsius with a quick hot air station or similar. Use good flux like Amtech NC-559-V2-TF. If this doesn’t provide a result you could than try to reflow them.

I suspect a temp of around 450 to 500 would do with airflow about half. You need to remember if the pads have become oxidised this will be only a temporary fix.

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I am new to reflow. So some questions:

1. You suggest I work on both chips or just on the video processor (LGE35230)?

2. I've just noticed that my board says it has Pb Free solder. With that being the case do your temperature recommendations still stand?

3. If just heat to 200 degrees, you mean I need a surface temp probe to confirm the 200 C, while setting the hot air station to 450-500 C (or do you mean station at 450-500 F)?

4. What temp stages (rate of climb, temp and duration, rate of cooling do you recommend?

5. Do you recommend using a heat source underneath (there is a bunch of small surface mount capacitors right under the video chip)?

6. Regarding good flux. My local electronics store has this:

https://leeselectronic.com/en/product/18...

is that good enough or would it be highly advisable to do mail order of the product you suggested?

由 tron 完成的 2021年7月9日

7. If this 'simple heating' fails, and I need to do a more thorough reflow, I am not planing to buy a pro reflow machine. If I am to do any of it, I will probably get a cheap reflow station for ~$90; good no-clean, liquid flux, possibly a surface temp probe and use a stove top for a hotplate if needed. How would you gage my chances for success with this simple armamentarium?

8. If a thorough reflow will be needed after all, I cannot find an exact match of my IC on alldatasheet.com. The closest I could come to it is: BCM352F110T300B00. It gives the info shown on the last picture. (I also know that the board uses Pb Free soldering.) But that is still not enough info for a profile and I don't know where to dig up a generic one. What profile would you suggest?

9. Finally, the heat sink has a thermal pad. Should I stick with it or replace it with thermal paste?

由 tron 完成的 2021年7月9日

@tronz I wasn’t sure what was under the heatsink. I am not sure what problem you are having with the TV but if it is a signature fault and this is the solution I think it would be the video processor (LGE35230).

When reflowing or removing BGA chips you have to take into account the ground plain and this comes with experience. I think these boards were put into an industrial oven.

I would try and source another board and practice on that. That is why I only suggested heating the chip up at 200 with some good flux.

由 Chris Stables 完成的 2021年7月10日

@imicrosoldering the diagnostic work up that led to this solution was done here:

TV stopped powering on

Please explain what you mean by 'the ground plain'?

由 tron 完成的 2021年7月11日

@tronz The ground plain usually determines how much heat the chip will need for the solder to melt. If a large amount of metal is connected to the ground circuit you would need to apply more heat. On some circuit boards there can be a whole layer of metal connected to the ground circuit.

I would defiantly check the power rails before trying to reflow. I cannot help with the diagnostic as I do not work on high voltage devices so I would be just guessing.

由 Chris Stables 完成的 2021年7月11日

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We would at least need some pics of the mainboard and BGA chip. — Chris Stables
@imicrosoldering there are two IC's under there. I suppose one is talking about the video processor which is marketed as a LGE35230 but it is a BCM35230kfsbg BGA IC — oldturkey03
I am new to reflow. So some questions:

1. You suggest I work on both chips or just on the video processor (LGE35230)?

2. I've just noticed that my board says it has Pb Free solder. With that being the case do your temperature recommendations still stand?

3. If just heat to 200 degrees, you mean I need a surface temp probe to confirm the 200 C, while setting the hot air station to 450-500 C (or do you mean station at 450-500 F)?

4. What temp stages (rate of climb, temp and duration, rate of cooling do you recommend?

5. Do you recommend using a heat source underneath (there is a bunch of small surface mount capacitors right under the video chip)?

6. Regarding good flux. My local electronics store has this:

https://leeselectronic.com/en/product/18...

is that good enough or would it be highly advisable to do mail order of the product you suggested? — tron
7. If this 'simple heating' fails, and I need to do a more thorough reflow, I am not planing to buy a pro reflow machine. If I am to do any of it, I will probably get a cheap reflow station for ~$90; good no-clean, liquid flux, possibly a surface temp probe and use a stove top for a hotplate if needed. How would you gage my chances for success with this simple armamentarium?

8. If a thorough reflow will be needed after all, I cannot find an exact match of my IC on alldatasheet.com. The closest I could come to it is: BCM352F110T300B00. It gives the info shown on the last picture. (I also know that the board uses Pb Free soldering.) But that is still not enough info for a profile and I don't know where to dig up a generic one. What profile would you suggest?

9. Finally, the heat sink has a thermal pad. Should I stick with it or replace it with thermal paste? — tron
@tronz I wasn’t sure what was under the heatsink. I am not sure what problem you are having with the TV but if it is a signature fault and this is the solution I think it would be the video processor (LGE35230).

When reflowing or removing BGA chips you have to take into account the ground plain and this comes with experience. I think these boards were put into an industrial oven.

I would try and source another board and practice on that. That is why I only suggested heating the chip up at 200 with some good flux. — Chris Stables
@imicrosoldering the diagnostic work up that led to this solution was done here:

TV stopped powering on

Please explain what you mean by 'the ground plain'? — tron
@tronz The ground plain usually determines how much heat the chip will need for the solder to melt. If a large amount of metal is connected to the ground circuit you would need to apply more heat. On some circuit boards there can be a whole layer of metal connected to the ground circuit.

I would defiantly check the power rails before trying to reflow. I cannot help with the diagnostic as I do not work on high voltage devices so I would be just guessing. — Chris Stables

LG Television

How to re-flow a BGA chip

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