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Old 11-29-2021, 08:09 AM   #1
jimbofz
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Default removing glued s/mount chips lg lb series

recently struggled to remove BL0202 backlight chip
which had red residue of glue underneath
as well as annoying laquer over the top and surrounding area.
i had to use more heat than i like to remove it
which can cause bubbling of the bcb
i used two different types of flux,but it was the glue causing the problem .
just wondered if anyone has had this problem ,and if there is any solvent that may loosen the glue before desoldering?
(some vestel fets are also glued the same way)
this was on a LG47 LB585V,
I had replaced the led strips which were badly discoloured only to find q806 mdhd 4n20y s/c
r840 burnt
and bl0202b s/c
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Old 11-29-2021, 04:35 PM   #2
CapLeaker
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Default Re: removing glued s/mount chips lg lb series

Cut the legs of with a knife, remove the chip, then desolder the rest of the legs on the pads.
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Old 11-30-2021, 06:46 AM   #3
jimbofz
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Default Re: removing glued s/mount chips lg lb series

thanks at least someone reads my posts
thats a good idea
but when salvaging a chip from a scrap board obvious wont work
so any thaughts on solvent to loosen the bond ?
this repair has caused me grief as the availibility of MDHT4N20Y fet
i could order from china but waiting 2 months is the problem
even the chip BL0202B are scarce in uk
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Old 11-30-2021, 07:28 AM   #4
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Default Re: removing glued s/mount chips lg lb series

Plenty of people read the posts, photos always help get a response.
I'm guessing the red glue is adhesive not underfil so a bit of heat and one of the BGA blades to cut it.
I'm not sure where you're ordering from but my stuff takes around 2 weeks from Aliexpress.
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Old 11-30-2021, 10:46 AM   #5
stj
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Default Re: removing glued s/mount chips lg lb series

philips use the red glue, you just heat the chip with hot air till the solder melts - then twist it with tweezers and the glue breaks.
it's weakened by the heat
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Old 11-30-2021, 11:27 AM   #6
jimbofz
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Default Re: removing glued s/mount chips lg lb series

Quote:
Originally Posted by stj View Post
philips use the red glue, you just heat the chip with hot air till the solder melts - then twist it with tweezers and the glue breaks.
it's weakened by the heat
what max temp would you suggest ? i normally use 250 degrees
i had to turn up to max to budge it which is not good for the pcb
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Old 11-30-2021, 11:30 AM   #7
jimbofz
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Default Re: removing glued s/mount chips lg lb series

Quote:
Originally Posted by diif View Post
Plenty of people read the posts, photos always help get a response.
I'm guessing the red glue is adhesive not underfil so a bit of heat and one of the BGA blades to cut it.
I'm not sure where you're ordering from but my stuff takes around 2 weeks from Aliexpress.
i must just be unlucky
aliexpress varies so much with del times
and quality of product is sometimes poor
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Old 11-30-2021, 04:41 PM   #8
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Default Re: removing glued s/mount chips lg lb series

Quote:
Originally Posted by jimbofz View Post
i must just be unlucky
aliexpress varies so much with del times
and quality of product is sometimes poor
When you order on Aliexpress the cheapest option of postage is always the longest. You can select a quicker speed of postage more expensive that gets delivery within a couple of weeks.
It is not intuitive to select the higher postage costs but it's generally available on all listings, as I recall you use a dropdown menu to select different options within your basket. Look and use sellers by the quantity of the orders and there feedback of the quality of the goods. Don't just buy product only on the basis of the price, which I am guessing you have done previously. You may pay a little extra but at least you will get it quicker and better quality.
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Old 11-30-2021, 05:21 PM   #9
stj
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Default Re: removing glued s/mount chips lg lb series

heat needs to be 300-350 really

as for ali, dont use "super cainiao" shipping, stick with ali standard or saver
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Old 12-01-2021, 07:47 AM   #10
jimbofz
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Default Re: removing glued s/mount chips lg lb series

Quote:
Originally Posted by stj View Post
heat needs to be 300-350 really

as for ali, dont use "super cainiao" shipping, stick with ali standard or saver
ive always tried to remove s/m components with the minimum temp
and then increase temp if the item is stubborn
and use the smallest nozzle on my s station
to prevent other close components flying off .
i will try 300-350 thanks
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Old 12-01-2021, 07:50 AM   #11
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Default Re: removing glued s/mount chips lg lb series

Quote:
Originally Posted by cheeky2 View Post
When you order on Aliexpress the cheapest option of postage is always the longest. You can select a quicker speed of postage more expensive that gets delivery within a couple of weeks.
It is not intuitive to select the higher postage costs but it's generally available on all listings, as I recall you use a dropdown menu to select different options within your basket. Look and use sellers by the quantity of the orders and there feedback of the quality of the goods. Don't just buy product only on the basis of the price, which I am guessing you have done previously. You may pay a little extra but at least you will get it quicker and better quality.
thanks thats good advice
i will follow it on next order
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