Re-balling or reflow an LG tv LGE35230 chip

[Serge125]

Hi all!!

    Ok my tv this morning was acting up again with bad video (pic) and 6 month ago I "re-flowed" with just a heat gun (yeah yeah I know but I didn't have a heat rework station back then), and for 6 months it worked but this morning well it came back to what it was bad picture. Now I KNOW that re-flowing isn't the BEST solution to fixing this problem but I need practice with my new quick 861dw but I know that I can re-flow the chip again until the next problem (in about 6 months) but is there a "proper" way to do it so it can last a bit more time before the problem occurs again or will last about 6 months (in my case). Now what would be the best temperature/air flow should I set my quick to do a good re-flow? The first time I did it with a heat gun I didn't use any flux should I use some or just heat it? I would be willing to do a re-ball in a future time (yeah in about 6 months) so I don't think there is any stencil for tv's bga chips so I'll have to add the balls one by one and I know that the size are .45 so any suggestions on heat/air flow for this or just use the same as re-flow? BTW I have a SainSmart MINIWARE MHP30 Mini Hot Plate Soldering Preheating Station that I gor from Amazon can I use this to re-flow instead of using my Quick and if so at what temperature can I set it?. THANKS for any help with this!!!

[TheMG]

I would use both the hot plate pre-heater and the hot air rework station. Set the hot plate under the board under the BGA, close but not touching the board. Preheat until the board is at around 150C or so. Don't go crazy with the preheat, the object is only to heat up the board enough to make the job easier with the hot air, minimizing how much time you need to apply the hot air before the solder flows.

Yes, absolutely do use flux! Use a liquid flux that can easily flow underneath the BGA and get to all the solder balls. Flux will greatly improve the chances of a successful reflow.

Heat with the hot air evenly just until you see the tiniest bit of movement of the BGA, indicating that all of the balls have melted (you may need to give the BGA just a gentle light nudge to check, surface tension of the melted solder will immediately cause the BGA to realign itself).

How big of a BGA is this anyways?

Good luck!

[Serge125]

I would use both the hot plate pre-heater and the hot air rework station. Set the hot plate under the board under the BGA, close but not touching the board. Preheat until the board is at around 150C or so. Don't go crazy with the preheat, the object is only to heat up the board enough to make the job easier with the hot air, minimizing how much time you need to apply the hot air before the solder flows.

Ok as for the hot plate I don't think that I can use it because there is allot of resistors and caps under that chip so I don't de-solder them with the plate. BTW at what temperature shouldI use on my Quick and airflow speed?

Yes, absolutely do use flux! Use a liquid flux that can easily flow underneath the BGA and get to all the solder balls. Flux will greatly improve the chances of a successful reflow.

I don't have any liquid flux just the syringe type, can I still use it? Anyway it's gonna melt with the heat so it should still do.

Heat with the hot air evenly just until you see the tiniest bit of movement of the BGA, indicating that all of the balls have melted (you may need to give the BGA just a gentle light nudge to check, surface tension of the melted solder will immediately cause the BGA to realign itself).

Gee if it moves I don't want the solder to "bridge", you know. I will put some aluminum around the chip because there are 2 chips nearby that they are both BGA too.

How big of a BGA is this anyways?

About an inch.

THANKS for your response!!

[amyk]

From the thumbnail I thought that was a Xilinx FPGA, but the LGE35230 is actually the same as a BCM35230 (i.e. a Broadcom part); and stencils are definitely available:

https://www.hklrf.com/LGE35230-Stencil-Template_4542.html

Given the heatspreader on the IC indicates that it likely dissipates a lot of powre, I suggest adding a heatsink and maybe even fan if it doesn't have one already.

[Serge125]

Well there is a big heat sink on it but it would be nice to add a slim fan but it won’t fit because space between the tv panel and main board. Maybe drill holes where the heat sink is could help draw the hot air out of the tv instead of staying in.

[amyk]

When reinstalling the heatsink, don't forget the thermal paste.

[Serge125]

When reinstalling the heatsink, don't forget the thermal paste.

Hi there and thanks!! There wasn't any thermal paste on it when I took off the heat sink, it's some kind of a gray "thermal?" tape on the heat sink but no thermal paste.

THANKS!!

[perieanuo]

thermal paste replacing that thermal pad, NO NO NO
it isn't so much difference in thermal conductivity between the pad and some conductive/risky paste
i have tested pads with almost same result as good paste, the paste needs some degree of precision
if you want cooling and you got the space, put a real heat dissipator like the ones for memories/raspberry pi's, they come cheap enough. then your heat dissipation is resolved
imho, reflow process is first about flux quality and second about heating profile
serious machines do bottom heating (at home i use also a heating plate with 120C for example) and top heating must respect temp/time for the flux to do his job, then you rise the temp and do the second reflow ramp/peak. i'd guess you can look at standard profiles and adapt, just don't overheat. i bet you got alloy without Pb and it's tricky

[perieanuo]

of course, you gotta clarify 'grey thermal' it's paste or pad? pictures pictures pictures....

[Serge125]

of course, you gotta clarify 'grey thermal' it's paste or pad? pictures pictures pictures....

Hi there here is a pic of what I have not mine but on a video that I saw a while back but it's the same tv as mine. I CLARIFY that it's a PAD NOT paste. The first time that opened it there were never a sing of paste what so ever just this square gray "thermal" pad.

[perieanuo]

yep it's a pad, and a pretty good one
anyway, i maintain my anterior oppinion