Author Topic: QFN IC Chip Will Not Desolder  (Read 7322 times)

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Offline SnechoTopic starter

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QFN IC Chip Will Not Desolder
« on: June 26, 2021, 08:07:37 am »
Hello all

I'm here because I was looking for advice on desoldering a QFN IC Chip. It has about 40 pins and a thermal pad/vias

I'm trying to replace the TDP158 Retimer Chip on an Xbox One X motherboard. I've watched at least a half dozen videos on how to replace it, where they use a hot air rework station to apply heat to the chip and remove it. They never use a preheater or anything like that, they just apply hot air over the whole chip and have it removed in about 15-30 seconds. Seems simple enough

The other day I attempted to do this myself. I tried 350C, 400C, 450C, and 500C with my hot air station, and after two minutes, the chip still would not budge. And now it's starting to break apart from the heat

Am I doing something wrong?

One video of what I'm talking about for reference: https://youtu.be/EaTw_2qQUg8?t=60
« Last Edit: June 26, 2021, 08:13:29 am by Snecho »
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Online ataradov

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Re: QFN IC Chip Will Not Desolder
« Reply #1 on: June 26, 2021, 08:43:10 am »
It is hard to tell if you are doing something wrong without seeing what you are doing. 500 C is definitely overkill.

When I need to remove a chip like this with a lot of thermal mass on the board, I set 350-400 C and lower air flow. Then basically do what they do in the video. Hold the nozzle close to the IC. Temperature drops very fast with the distance.

You don't need to hold the IC with the tweezers. It is enough to just poke it on the side. Once the solder is melted, it will just move to the solder mask around.

I would also try to find some scrap boards and train on them first. If you have issues removing the chip, then soldering it back is likely to not go smoothly either.
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Offline Microdoser

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Re: QFN IC Chip Will Not Desolder
« Reply #2 on: June 26, 2021, 09:14:16 am »
I agree, low flow, 350C, keep the nozzle on the chip, plenty of flux.

What air gun station do you have? They are not all made equal after all.
« Last Edit: June 26, 2021, 01:13:15 pm by Microdoser »
 

Offline ambrosia heart

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Re: QFN IC Chip Will Not Desolder
« Reply #3 on: June 26, 2021, 10:30:51 am »
See what he did may help you.
500°C did more harm than good than in motherboard.
This temperature damaged pads; lift off pads.

Heat board in both sides. :popcorn:

 

Offline aqibi2000

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Re: QFN IC Chip Will Not Desolder
« Reply #4 on: June 26, 2021, 12:00:44 pm »
You need to use some form of preheater, the thermal mass of the board is far too great
Tinkerer’
 
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Offline PA4TIM

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Re: QFN IC Chip Will Not Desolder
« Reply #5 on: June 26, 2021, 12:15:03 pm »
I think he needs a better hot air station.  I never crank up mine that high and I only once needed a preheater but that was an extreme situation.  I have seen videos of people unboxing and trying cheap (under 200 dollar) Chinese hot air stations and they were struggling with things my old OKI does in less then 10 seconds.

A good station measures the air so you have the set temp un-depended of the airflow. Cheap stations cool down a lot if you increase the airflow and you have to crank them up by hand to compensate. If so, leave the airflow low, use a IR or TC tempmeter to check what happens on a chip while practicing/experimenting. .

Besides that, you need some experience so practice on some old pcbs first.
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Offline Microdoser

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Re: QFN IC Chip Will Not Desolder
« Reply #6 on: June 26, 2021, 01:14:29 pm »
After looking at the video, that chip has a big pad. I have never had a problem with my Atten, no matter the size of pad on a chip.

What hot air station are you using?
 

Offline Bud

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Re: QFN IC Chip Will Not Desolder
« Reply #7 on: June 26, 2021, 02:00:47 pm »
If it is a multilayer board with ground plane(s), desoldering may be difficult. I would preheat the board from below to 100-120 C, then hit the chip with hot air.
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Offline madires

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Re: QFN IC Chip Will Not Desolder
« Reply #8 on: June 26, 2021, 02:35:54 pm »
Yep, in case of a thermal pad I preheat the other side first with hot air, flip the board, and then desolder the IC. Usually I set the hot air station to around 320 - 350 °C for desoldering. For preheating I use the same temperature setting (too lazy to change) but increase the distance to the board.
 

Offline Mario87

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Re: QFN IC Chip Will Not Desolder
« Reply #9 on: June 26, 2021, 10:05:54 pm »
Agree with what others have said and also want to add use lots of good quality flux!! Makes a world of difference.
 

Offline narkeleptk

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Re: QFN IC Chip Will Not Desolder
« Reply #10 on: June 27, 2021, 12:33:22 am »
When things dont like to come off for me I use 2 hot air guns @ 450C. I work a lot on things still attached to aluminum cases tho. Normal things 350C is good enough.
 

Offline PA4TIM

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Re: QFN IC Chip Will Not Desolder
« Reply #11 on: June 27, 2021, 12:47:02 am »
Sometimes parts are glued to the PCB, but you can see that (red stuff peeping out under resistors and caps)
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Offline SnechoTopic starter

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Re: QFN IC Chip Will Not Desolder
« Reply #12 on: June 27, 2021, 04:02:53 am »
Thanks for all the feedback thus far
It is hard to tell if you are doing something wrong without seeing what you are doing. 500 C is definitely overkill.

When I need to remove a chip like this with a lot of thermal mass on the board, I set 350-400 C and lower air flow. Then basically do what they do in the video. Hold the nozzle close to the IC. Temperature drops very fast with the distance.

You don't need to hold the IC with the tweezers. It is enough to just poke it on the side. Once the solder is melted, it will just move to the solder mask around.

I would also try to find some scrap boards and train on them first. If you have issues removing the chip, then soldering it back is likely to not go smoothly either.
Yeah, I agree with you it's hard to tell what exactly I'm doing from the original post alone. Allow me to elaborate

I do pretty much what you stated, and what they do in all the videos. I set my temperature to 350C at first, and 50% airflow. Then I started applying hot air from a few inches away to the chip area to warm up the board, and then moved the nozzle a few millimeters from the chip and applied heat directly to the chip while moving the nozzle in small circular motions. As you said, I did not hold the chip with tweezers. I held them close by and poked the chip every 10 seconds or so. After about 45 seconds, the chip still would not budge. That's when I started increasing the temperature and kept applying heat a few millimeters away from the IC and moving the nozzle in small circular motions

As for practicing on scrap boards, I have a few that I've been desoldering and soldering various chips on for a week. I've never had an issue removing a chip from them. Quite odd

Also, Я видел ваш сайт и говорю по-русски, если вы тоже. У вас довольно впечатляющая и интересная история. Мой тоже похож на моего отца :)
I agree, low flow, 350C, keep the nozzle on the chip, plenty of flux.
Yep, that's what I've been doing. One thing to note though is I used white generic flux paste and applied it to the chip with a cotton swab. Reference: https://www.amazon.com/Delcast-Rosin-Soldering-Flux-Paste/dp/B00SVESNTC/ref=sr_1_2?dchild=1&keywords=delcast+flux&qid=1624762597&sr=8-2

However, today I got a soldering shipment in, and now have Chip-Quik Tack Flux. The kind that comes in a syringe. Reference: https://www.amazon.com/gp/product/B08KJPG3NZ/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

Admittedly, understanding flux is one of my weaker points in soldering knowledge, but I've been getting along until this point by using common sense, and the way my father taught me to solder many years ago. And outside of that, using whatever kind of flux they use in whatever instructions or video I'm attempting to follow
What air gun station do you have? They are not all made equal after all.
After looking at the video, that chip has a big pad. I have never had a problem with my Atten, no matter the size of pad on a chip.

What hot air station are you using?
I think he needs a better hot air station.  I never crank up mine that high and I only once needed a preheater but that was an extreme situation.  I have seen videos of people unboxing and trying cheap (under 200 dollar) Chinese hot air stations and they were struggling with things my old OKI does in less then 10 seconds.

A good station measures the air so you have the set temp un-depended of the airflow. Cheap stations cool down a lot if you increase the airflow and you have to crank them up by hand to compensate. If so, leave the airflow low, use a IR or TC tempmeter to check what happens on a chip while practicing/experimenting. .
The hot air rework station I'm using is the X-Tronic 6020-PRO-X. Link: https://xtronicusa.com/products/hot-air-rework-stations-parts/X-Tronic-6020-PRO-X-%E2%80%A2-Platinum-Series-%E2%80%A2-750-Watt-%E2%80%A2-Hot-Air-Rework-Station-%E2%80%A2-3-Temp-Presets-Temp-Calibration-Func-C-F-Func-Auto-Cool-Down-Standby-Mode-Mute-Unmute-Sound-&-Patented-Nozzle-Holder-p278541017

I got it because I didn't want to get a cheap no-name $50 one from Amazon, and I love my X-Tronic soldering iron so I thought it would pair nicely with it
500°C did more harm than good than in motherboard.
This temperature damaged pads; lift off pads.
Thanks for the feedback. Yes, I agree, 500C seems a bit excessive
Besides that, you need some experience so practice on some old pcbs first.
Agreed, that's why I have a few that I've been desoldering and soldering various chips on for a week. I've never had an issue removing a chip from them. Quite odd
If it is a multilayer board with ground plane(s), desoldering may be difficult. I would preheat the board from below to 100-120 C, then hit the chip with hot air.
I'm sure it could work, just seems odd that not one person in the half dozen videos I've seen uses a preheater or something to heat the board from below, and yet they always successfully remove the chip 🤔
Yep, in case of a thermal pad I preheat the other side first with hot air, flip the board, and then desolder the IC. Usually I set the hot air station to around 320 - 350 °C for desoldering. For preheating I use the same temperature setting (too lazy to change) but increase the distance to the board.
Yes that could work, again just seems odd no one else doing this repair has used a form of preheating
Agree with what others have said and also want to add use lots of good quality flux!! Makes a world of difference.
As with my reply to Microdoser, I used white generic flux paste and applied it to the chip with a cotton swab. Reference: https://www.amazon.com/Delcast-Rosin-Soldering-Flux-Paste/dp/B00SVESNTC/ref=sr_1_2?dchild=1&keywords=delcast+flux&qid=1624762597&sr=8-2

However, today I got a soldering shipment in, and now have Chip-Quik Tack Flux. The kind that comes in a syringe. Reference: https://www.amazon.com/gp/product/B08KJPG3NZ/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

Admittedly, understanding flux is one of my weaker points in soldering knowledge, but I've been getting along until this point by using common sense, and the way my father taught me to solder many years ago. And outside of that, using whatever kind of flux they use in whatever instructions or video I'm attempting to follow
When things dont like to come off for me I use 2 hot air guns @ 450C. I work a lot on things still attached to aluminum cases tho. Normal things 350C is good enough.
Unfortunately, I do not have two hot air stations, but that would seem rather excessive in this situation
Sometimes parts are glued to the PCB, but you can see that (red stuff peeping out under resistors and caps)
I definitely don't think it's glued on, as it's never been seen or mentioned in any of the videos
« Last Edit: June 27, 2021, 04:20:29 am by Snecho »
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Offline dc101

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Re: QFN IC Chip Will Not Desolder
« Reply #13 on: June 27, 2021, 08:01:15 am »
Might be worth taking some regular solder and trying to mix it in with the existing solder using a regular soldering iron. Just put a blob on your iron and run it thoroughly over the exposed pads. And yes definitely need to be using flux. I would highly recommend the YouTube channel NorthridgeFix if you're interested in electronics repair.

He did a video where he replaced that exact IC you're trying to replace:

Cheers
« Last Edit: June 27, 2021, 08:10:38 am by dc101 »
 

Offline PA4TIM

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Re: QFN IC Chip Will Not Desolder
« Reply #14 on: June 27, 2021, 10:49:01 am »
50 dollar hot air stations are toys, under 200 they are usable for easy jobs done by a skilled person, good stations that can handle everything, also difficult jobs like this one, cost over 500 dollar upto 1500 dollar. Louis Rossmann has some videos over this. In one he tells people who ask if they can have a cheap one instead of the "expensive" Hakko., "the Hakko is the cheap one"  >:D (i saw a video about your station, it was really struggling to remove a smd resistor. That is very bad

If you do exactly the same as in the videos then the only thing left is your station. They are usable for removing easy to remove parts. Multilayer, heat-tabs, older solder, dirt etc makes it much more difficult. Adding fresh solder, flux etc (all the tips already stated in this topic) can help but if a station just does not has enough power even a pro can not get the parts off.

Be careful with flux paste, never use the plumber stuff, it will eat away traces and vias. Use a good solder that has flux inside. (that Chip Quick from your link looks a lot different from the stuff I have, are you sure it is no fake ? )

But have you thought about the next step, removing is often the easy part, cleaning can be done by wick or a desolder station, but resoldering a new one is often more difficult as removing. The pads must be 100% flat and clean, then the tin must melt everywhere at the same time and stays that so the part can "float" to centre. Flux !!

An other option is to use a paintstripper to preheat (When I did not have a hotair station I used a paintstripper. I made a nozzle for it from welding a cone from sheetmetal. Worked great but a bit dangerous, that thing was 2200W. My desolder station is only 900W(heatpower) but thanks to the good regulation and element design it is in normal use pretty powerful. It is like audio, you have audio Watts and "ohms law based" real watts. And sometimes the whole device pulls X watt, not stating how much is lost between mains plug and the tip of the handpiece. And how efficient the heater is. A1000W nail as element will not be as succesful as a optimal designed 500W heater and airflow path.
« Last Edit: June 27, 2021, 11:49:19 am by PA4TIM »
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Offline dc101

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Re: QFN IC Chip Will Not Desolder
« Reply #15 on: June 27, 2021, 04:45:43 pm »
Chip Quick is legit, I've used their flux before and I use their low-melt solder at work. Their market is more focused on rework/repair as opposed to companies like Amtech.
« Last Edit: June 27, 2021, 07:13:50 pm by dc101 »
 

Offline narkeleptk

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Re: QFN IC Chip Will Not Desolder
« Reply #16 on: June 27, 2021, 07:01:00 pm »
When things don't like to come off for me I use 2 hot air guns @ 450C. I work a lot on things still attached to aluminum cases tho. Normal things 350C is good enough.
Unfortunately, I do not have two hot air stations, but that would seem rather excessive in this situation
Says the guy who has not been able to remove the IC.... Personally, I have no problem removing a 40-Pin WQFN or any other IC. I have a few rework stations but I use the same 6040-pro-x your trying to use most of the time. Its plenty capable.

The problem is simple. You do not have enough heat getting to the thermal pad. You can achieve this many different ways.

A few idea's
Pre-heater,
Another hot air gun (from bottom is best, top if no access to bottom)
Large tip soldering iron placed on bottom of PCB if thermal pad goes all the way through.

Use a scalpel type razor to gently lift at the chip and scratch around the pins while heating.

Side note about extra air, if your desperate. It doesn't need to be a fancy rework station. A cheap paint stripper like this: https://www.harborfreight.com/1500-watt-11-amp-dual-temperature-heat-gun-56434.html
Will work just fine for the extra heating needed. Your basically just using it as a pre-heater while your real rework gun is your main tool.
 
 
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Offline SnechoTopic starter

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Re: QFN IC Chip Will Not Desolder
« Reply #17 on: June 28, 2021, 05:15:50 am »
Might be worth taking some regular solder and trying to mix it in with the existing solder using a regular soldering iron. Just put a blob on your iron and run it thoroughly over the exposed pads. And yes definitely need to be using flux. I would highly recommend the YouTube channel NorthridgeFix if you're interested in electronics repair.

He did a video where he replaced that exact IC you're trying to replace:

Cheers
Hahaha, I've been binge watching NorthridgeFix for the past two weeks. In fact, the video example I linked in the original post of a retimer IC getting replaced was by NorthridgeFix

But yeah, I've thought about carefully adding more solder to the pads. Might be worth a shot
50 dollar hot air stations are toys, under 200 they are usable for easy jobs done by a skilled person, good stations that can handle everything, also difficult jobs like this one, cost over 500 dollar upto 1500 dollar. Louis Rossmann has some videos over this. In one he tells people who ask if they can have a cheap one instead of the "expensive" Hakko., "the Hakko is the cheap one"  >:D (i saw a video about your station, it was really struggling to remove a smd resistor. That is very bad

If you do exactly the same as in the videos then the only thing left is your station. They are usable for removing easy to remove parts. Multilayer, heat-tabs, older solder, dirt etc makes it much more difficult. Adding fresh solder, flux etc (all the tips already stated in this topic) can help but if a station just does not has enough power even a pro can not get the parts off.

Be careful with flux paste, never use the plumber stuff, it will eat away traces and vias. Use a good solder that has flux inside. (that Chip Quick from your link looks a lot different from the stuff I have, are you sure it is no fake ? )

But have you thought about the next step, removing is often the easy part, cleaning can be done by wick or a desolder station, but resoldering a new one is often more difficult as removing. The pads must be 100% flat and clean, then the tin must melt everywhere at the same time and stays that so the part can "float" to centre. Flux !!

An other option is to use a paintstripper to preheat (When I did not have a hotair station I used a paintstripper. I made a nozzle for it from welding a cone from sheetmetal. Worked great but a bit dangerous, that thing was 2200W. My desolder station is only 900W(heatpower) but thanks to the good regulation and element design it is in normal use pretty powerful. It is like audio, you have audio Watts and "ohms law based" real watts. And sometimes the whole device pulls X watt, not stating how much is lost between mains plug and the tip of the handpiece. And how efficient the heater is. A1000W nail as element will not be as succesful as a optimal designed 500W heater and airflow path.
Hmmm, you make pretty valid points. Is it ok if I ask what makes a good hot air station in your opinion then? Like for example you mentioned "power." Because $50-$1500 is a really huge variance. Especially since they all seem to do the same basic thing, i.e. temp control, air flow control, and all have a temperature range of around 100C-500C. Or perhaps I'm overlooking something

I realize most people on this forum are electrical vets that do this for a living. However despite my background of always being in and around electrical engineering, I've always been more of a tinkerer/hacker/hobbyist. That's probably why an $800-$1500 hot air station just didn't seem feasible for me, as that's more of a professional market. Also perhaps a reason I went with the mid-tier $150 X-Tronic one

Yep, my solder is rosin core leaded solder. And if you're asking if the flux is a fake Chip-Quik, I doubt it, as it came with all the official Chip-Quik paperwork

And yes I have thought about next step of resoldering quite a bit. In all the videos, each person does it a bit differently. As with many things with soldering, there is not really one definitive way. I have to take all the methods into consideration and do it my own way
Chip Quick is legit, I've used their flux before and I use their low-melt solder at work. Their market is more focused on rework/repair as opposed to companies like Amtech.
i went with the Chip-Quik syringe as my first flux syringe because it looked similar to the type of flux used in the videos and had a good price. I do hope it works in the same fashion. My other choice was the MG Chemicals flux syringe, as I do love MG Chemicals, but it was more expensive, and I had already settled on the Chip-Quik flux
When things don't like to come off for me I use 2 hot air guns @ 450C. I work a lot on things still attached to aluminum cases tho. Normal things 350C is good enough.
Unfortunately, I do not have two hot air stations, but that would seem rather excessive in this situation
Says the guy who has not been able to remove the IC.... Personally, I have no problem removing a 40-Pin WQFN or any other IC. I have a few rework stations but I use the same 6040-pro-x your trying to use most of the time. Its plenty capable.

The problem is simple. You do not have enough heat getting to the thermal pad. You can achieve this many different ways.

A few idea's
Pre-heater,
Another hot air gun (from bottom is best, top if no access to bottom)
Large tip soldering iron placed on bottom of PCB if thermal pad goes all the way through.

Use a scalpel type razor to gently lift at the chip and scratch around the pins while heating.

Side note about extra air, if your desperate. It doesn't need to be a fancy rework station. A cheap paint stripper like this: https://www.harborfreight.com/1500-watt-11-amp-dual-temperature-heat-gun-56434.html
Will work just fine for the extra heating needed. Your basically just using it as a pre-heater while your real rework gun is your main tool.
Sorry, I didn't mean to offend. I thought you meant aim two hot air guns at the chip @450C, in which case, I made the assumption that that seemed excessive, as ataradov and ambrosia heart pointed out to me that just one hot air gun @500C is overkill

Many thanks for reassuring me about the hot air station I'm using though. And you seem to have a good point about the extra pre-heating that may be needed. i may have to try that
« Last Edit: June 28, 2021, 05:21:13 am by Snecho »
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Offline perieanuo

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Re: QFN IC Chip Will Not Desolder
« Reply #18 on: June 28, 2021, 09:15:57 am »
hi,
even with 80usd hotair station for chips with some big gnd pad, your chances are multiplied by 10 if you use a heating plate below the pcb (first, you reduce overheat, you reduce curbe radius and component stressing for pcb caused by one-side only heating)
what everyone says, quality flux is a must, but someone who works with bga soldering, heating up AND bottom pcb is also a must
watch pro soldering stations like metcal 5000 hotair series, they heat on both sides.
btw, i saw mobos with more than 1cm flexing even with that method, for big pcb's you need to stabilise mechanically the board even better than a 25 000 euros reworking machine
or like the cheap chinese reworking machines, with quartz bottom heater, they were like 300-400 euros some years ago, i bet they work fine enough for the money, at least for small boards
but, you cab manage to do yourself something similar, maybe a little more $$$ but more reliable (me personal bottom heater board witk 2x800w heating resistances incorporated in Aluminium aviation plates was less than 100 euros, of course with some spare parts from my drawer (temperature controller, threaded temperature sensor into ALU plate etc)
the secret for pro soldering bga workshop, BOTTOM HEATING, don't need to buy 600 euros equipment, i work sometimes with atten 8502d, 200 euros, plus 100 euros heating plate or why not, a second 80 euros hotair rework station as bottom heater (it was a project on r&d company i never finished :) , i changed job)
 

Offline Ian.M

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Re: QFN IC Chip Will Not Desolder
« Reply #19 on: June 28, 2021, 09:56:46 am »
Its possible to use a 50W 12V MR16 halogen bulb as an improvised local area board preheater.  If you can still get hold of halogen bulbs, and can scrounge the rest of the parts (i.e. are a serious skip-rat, as many halogen installations are being scrapped and replaced with LED fixtures) you can probably put something together with change from $10.   If you have to order in parts and materials, it gets more expensive.  See https://www.eevblog.com/forum/manufacture/small-bottom-heater-for-rework-and-reflow/msg3427730/#msg3427730 for details.

I believe the Xbox One X board has decoupling caps and a few other components on the underside.  Mask them off with aluminum foil with a window cut under the offending chip location (3x to 4x the width of the chip)  and Kapton tape round the window and strategically at the board edges, so you don't knock off other parts while orbiting the board over the heater lamp, and don't turn the heat all the way up, as you don't want it to get quite hot enough to melt solder on its own without the localized hot air from the top side.  Practice on a scrap board with similar package ICs is essential.
 
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Offline SnechoTopic starter

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Re: QFN IC Chip Will Not Desolder
« Reply #20 on: June 28, 2021, 11:55:21 pm »
hi,
even with 80usd hotair station for chips with some big gnd pad, your chances are multiplied by 10 if you use a heating plate below the pcb (first, you reduce overheat, you reduce curbe radius and component stressing for pcb caused by one-side only heating)
what everyone says, quality flux is a must, but someone who works with bga soldering, heating up AND bottom pcb is also a must
watch pro soldering stations like metcal 5000 hotair series, they heat on both sides.
btw, i saw mobos with more than 1cm flexing even with that method, for big pcb's you need to stabilise mechanically the board even better than a 25 000 euros reworking machine
or like the cheap chinese reworking machines, with quartz bottom heater, they were like 300-400 euros some years ago, i bet they work fine enough for the money, at least for small boards
but, you cab manage to do yourself something similar, maybe a little more $$$ but more reliable (me personal bottom heater board witk 2x800w heating resistances incorporated in Aluminium aviation plates was less than 100 euros, of course with some spare parts from my drawer (temperature controller, threaded temperature sensor into ALU plate etc)
the secret for pro soldering bga workshop, BOTTOM HEATING, don't need to buy 600 euros equipment, i work sometimes with atten 8502d, 200 euros, plus 100 euros heating plate or why not, a second 80 euros hotair rework station as bottom heater (it was a project on r&d company i never finished :) , i changed job)
Its possible to use a 50W 12V MR16 halogen bulb as an improvised local area board preheater.  If you can still get hold of halogen bulbs, and can scrounge the rest of the parts (i.e. are a serious skip-rat, as many halogen installations are being scrapped and replaced with LED fixtures) you can probably put something together with change from $10.   If you have to order in parts and materials, it gets more expensive.  See https://www.eevblog.com/forum/manufacture/small-bottom-heater-for-rework-and-reflow/msg3427730/#msg3427730 for details.

I believe the Xbox One X board has decoupling caps and a few other components on the underside.  Mask them off with aluminum foil with a window cut under the offending chip location (3x to 4x the width of the chip)  and Kapton tape round the window and strategically at the board edges, so you don't knock off other parts while orbiting the board over the heater lamp, and don't turn the heat all the way up, as you don't want it to get quite hot enough to melt solder on its own without the localized hot air from the top side.  Practice on a scrap board with similar package ICs is essential.
Okay, definitely looks like using a form of pre-heater is becoming a running theme. Definitely seems like a good suggestion, and I think I will have to use this method

Thanks for the suggestions 🙂
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Offline Rasz

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Re: QFN IC Chip Will Not Desolder
« Reply #21 on: June 29, 2021, 03:16:04 am »
I think he needs a better hot air station.  I never crank up mine that high and I only once needed a preheater but that was an extreme situation.  I have seen videos of people unboxing and trying cheap (under 200 dollar) Chinese hot air stations and they were struggling with things my old OKI does in less then 10 seconds.

nowadays $200 is the realm of 1KW Quick 861DW, even HCT-1000 is half the power at 10x the price

The hot air rework station I'm using is the X-Tronic 6020-PRO-X
I got it because I didn't want to get a cheap no-name $50 one from Amazon

well, you didnt want it, yet thats precisely what you got :( Your "station" is just a fancy digital triac controller regulating power to the same heater hand piece used in all those $30 hotairs, with integrated pissant fan.

Yes that could work, again just seems odd no one else doing this repair has used a form of preheating

thermal mass - your station is pushing less hot air
technique - nozzle size and shape, distance, angle, airflow - those are as important as the temperature set

Stop looking at all the temperature figures thrown around, or the one on your station, those numbers are all meaningless. The only thing that matters is the temperature at the component you are trying to desolder and surrounding PCB, and nobody is measuring that.
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Offline Microdoser

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Re: QFN IC Chip Will Not Desolder
« Reply #22 on: June 29, 2021, 10:59:15 am »

 seems odd that not one person in the half dozen videos I've seen uses a preheater or something to heat the board from below, and yet they always successfully remove the chip 🤔

...

 I got a soldering shipment in, and now have Chip-Quik Tack Flux. The kind that comes in a syringe.

Yes, that's the sort of flux I know, I've never used the white stuff.

Regarding your hot air station, they are not made equal and generally come in two types. The sort that has the blower in the handle and the sort that has it in the main box. The handle blower type don't seem nearly as able as the other type, especially with difficult chips. Sorry to say it, but for the money, IMO you could have got a much better hot air station. The Atten ST-862D is the one I have, and I have not found any chip it cannot remove and rework.

Also, as has been said, the nozzle you have on the end affects things greatly.

A few years back, hot air stations were a lot of money, to the point where it was noted that the price dropped from ~$850 to $300



A little while later, that price dropped again



To compare handle blower types to integrated blower types, by someone who doesn't have years of specialist experience (also with a hot air station more in the price range of your station):



In the last video, he has some strong words to say about the handle blower type of hot air station...
« Last Edit: June 29, 2021, 11:06:20 am by Microdoser »
 

Offline narkeleptk

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Re: QFN IC Chip Will Not Desolder
« Reply #23 on: June 29, 2021, 11:10:35 pm »
Regarding your hot air station, they are not made equal and generally come in two types. The sort that has the blower in the handle and the sort that has it in the main box. The handle blower type don't seem nearly as able as the other type, especially with difficult chips. Sorry to say it, but for the money, IMO you could have got a much better hot air station. The Atten ST-862D is the one I have, and I have not found any chip it cannot remove and rework.


I see a lot of posts trying to say blah blah blah cheap hot air stations.  How many have used the unit TS is using? I regularly use the the same hot air station he's working with it and I can say from experience its perfectly fine to do this job. @ $150 for a solid built hot air gun and iron, Its an excellent unit for any hobbyist. I highly recommend it. I never liked handle blowers before but the one in this unit is quiet and works very well. Its one of the reason I've been using this machine over some of my more expensive units.  Both iron and air gun heats up quickly and accurately. My only gripe is the unit itself is a bit light on the back end and the irons cable is too short.

 

Offline Rasz

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Re: QFN IC Chip Will Not Desolder
« Reply #24 on: June 30, 2021, 05:34:16 am »
Regarding your hot air station, they are not made equal and generally come in two types. The sort that has the blower in the handle and the sort that has it in the main box. The handle blower type don't seem nearly as able as the other type, especially with difficult chips. Sorry to say it, but for the money, IMO you could have got a much better hot air station. The Atten ST-862D is the one I have, and I have not found any chip it cannot remove and rework.


I see a lot of posts trying to say blah blah blah cheap hot air stations.  How many have used the unit TS is using? I regularly use the the same hot air station he's working with it and I can say from experience its perfectly fine to do this job. @ $150 for a solid built hot air gun and iron, Its an excellent unit for any hobbyist. I highly recommend it. I never liked handle blowers before but the one in this unit is quiet and works very well. Its one of the reason I've been using this machine over some of my more expensive units.  Both iron and air gun heats up quickly and accurately. My only gripe is the unit itself is a bit light on the back end and the irons cable is too short.

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