question related to gpu cores and memory chips related tools please help

[Thabet]

hello guys
 I'm searching for a preheater in my country and the only thing I could find is this one:

https://vi.aliexpress.com/item/1005005551723613.html?spm=a2g0n.shoppingtesla.mainproduct.d0.6171TkLKTkLKxh&pdp_npi=3%40dis!ILS!₪341.49!₪204.89!!!!!%402101fb1217067477711653832e2b5a!12000033512725995!btf!!&afTraceInfo=1005005551723613__unknown__c_ppc_item_bridge_lp__QwdPwzF__1706747771371&gatewayAdapt=glo2vnm

in case you don't want to click on the link its sunshine S-918E

Could I use it for gpu core and ram chips removal and reballing?

And can you guys suggest me a good flux and solder paste and stencils to get from AliExpress for gpu core and ram chips reballing and removal

[Nominal Animal]

It does not get hot enough.  It is intended to separate LCD screen components, and as such, won't heat much above 130°C.  (See here at their home page, and compare to e.g. even more powerful LCD separator at Banggood, which only heats up to 130°C.)

You'll want one that can heat up to 350°C or so –– even though normally you'll use it at a lower temperature, you want it to have enough heating power to make the heating fast enough.  I see 850W ones for 200mm×200mm area; "Uyue 946C" seems a valid option: see this teardown and review at youtube.  If you check Aliexpress, you should find these (check the power and area!) for 70€-90€ shipped.

[Thabet]

Isn't something that reach 350° might cause the components from the side of the preheater to fall off?
And a friend of mine from other country suggested me that I only get something with air mesh and he said that only something with air mesh work with gpus core and memory chips is he correct?
What about the flux and paste and stencils any suggestion?

[Thabet]

Another question what is the temperature I need to set preheater to before using heat gun directly to core

[wraper]

I see 850W ones for 200mm×200mm area; "Uyue 946C" seems a valid option: see this teardown and review at youtube.  If you check Aliexpress, you should find these (check the power and area!) for 70€-90€ shipped.

Too small for computer HW. You need preheater that is at least as large as the board heated, otherwise there will be PCB warping during BGA reflow. Also I have almost the same preheater and find it not suitable for such jobs. Due to shiny surface it works poorly as preheater as there is barely any heat transfer through IR radiation and convection is all you can count on, which means it's nearly useless away from center as cold air will mix in. You'd need to anodize the aluminum plate first for it to become a half-decent preheater. Not to say plate itself is significantly hotter in the center.

[wraper]

Isn't something that reach 350° might cause the components from the side of the preheater to fall off?

PCB will never heat even close to preheater temperature. It's not like you're putting PCB in the oven where 350^oC is all around. Not to say most of components are held by solder surface tension when it melts. Only something as heavy as large inductors may fall down.

[Thabet]

So what other preheater you suggest to me?

[wraper]

Something like these would do
https://www.aliexpress.com/item/3256805031905357.html
https://www.aliexpress.com/i/3256804248514561.html?gatewayAdapt=4itemAdapt
But it would be preferable to paint the surface with black high temperature paint.

[wraper]

Also you should get PTFE PCB stands like on the pic. Dual rail or 4 point holders often won't keep PCB flat enough.

[Thabet]

These 2 are very big and if I order them with the custom fee it's gonna be very expensive to be honest
Is there another suggestion for me some one suggested this to me :
https://www.aliexpress.com/item/1005003893477558.html?spm=a2g0o.productlist.main.1.33c26de9kCZ4C9&algo_pvid=5b301714-b442-4c57-9240-69c7f5455371&algo_exp_id=5b301714-b442-4c57-9240-69c7f5455371-0&pdp_npi=4%40dis%21USD%21214.67%2196.60%21%21%21214.67%2196.60%21%40210307bf17062186267064290e15b9%2112000035629669091%21sea%21LB%213427891715%21&curPageLogUid=hWoTRXwaueOM&utparam-url=scene%3Asearch%7Cquery_from%3A
What do you think?

[wraper]

^ As I already said, preheater must be at least as large as a whole board, preferably somewhat larger. Otherwise PCBs will be warping. Some boards will be possible to rework successfully but other will warp like banana and you won't be able to successfully solder large BGA no matter how hard you try. Also the larger BGA chip size, the flatter PCB needs to be. You probably will have more success than failure with something of a size of GP104 (GTX1080 GPU chip), but with something of a size of GA102 (RTX2080 Ti) it will be outright doomed to fail.
Not to say I suggested preheater with flat plate is because they can be used with separate stands placed in many PCB holes. That allows the board to rest on the flat plate in multiple points and flatten out when hot. Holder like in the post above is absolutely incapable to keep the board flat in my experience. It's ok if you need to replace some resistor or MOSFET, but not GPU or any other large BGA.

[Thabet]

OK I will take what you said in consideration

What about stencils and solder paste and flux for gpu core and ram chips removing and reballing any suggestion

[wraper]

I suggest solder balls, rather than paste for most of things. As of stencils, if on cheap side, use direct heat ones. Be aware that some of them are utter garbage, some more or less OK for the same price. Otherwise get proper chip holders and more expensive stencils. For RAM, unless doing one off job, you probably should get holders/stencils for doing 4 or 8 chips at once. For reball, you could use cheap Kingbo RMA-218 garbage flux applied in thin layer. Then more of it and repeated heating after initial melting of the balls. Then clean that with IPA or alcohol based cleaner. For reflow on the board, I'd use some better genuine flux not from China. Or at least get Chinese branded stuff not cheaper than $10 for 100g, not fake Amtech. White creamy types seems to be more or less OKish.

[MarkT]

Due to shiny surface it works poorly as preheater as there is barely any heat transfer through IR radiation

Don't think that's true unless its metal - metals have low emissivity, almost everything else is high emissivity at 10µm wavelength which is relevant to these sorts of temperature. https://en.wikipedia.org/wiki/Emissivity. (check the value for glass....)

[wraper]

Due to shiny surface it works poorly as preheater as there is barely any heat transfer through IR radiation

Don't think that's true unless its metal - metals have low emissivity, almost everything else is high emissivity at 10µm wavelength which is relevant to these sorts of temperature. https://en.wikipedia.org/wiki/Emissivity. (check the value for glass....)

If you would actually google it or watch the video on the link, you'd see it's a shiny aluminum plate. Not to say I wrote it's aluminum in the part of the post you cut off.

[Thabet]

can you give me alink of the not fake amtech or chinese branded or even a good flux from aliexpress please ?

[Thabet]

i searched alot in aliexpress for PTFE PCB stands and i didn't find any is there another name for them?

[MarkT]

Doh I was looking at the wrong video.  Yes Al won't be emissive unless anodized (which is actually very high emissivity).

[Thabet]

i only could find the ptfe stands on russian sites with preheater station buyt not on aliexpress

[Thabet]

Yaxun 862d++
Is it good for gpu, ram remove and reball?

[MathWizard]

Isn't something that reach 350° might cause the components from the side of the preheater to fall off?

PCB will never heat even close to preheater temperature. It's not like you're putting PCB in the oven where 350^oC is all around. Not to say most of components are held by solder surface tension when it melts. Only something as heavy as large inductors may fall down.

So for typical SMD resistors/caps/inductors, with packages like 0805, surface tension is usually enough to hold up them upside down ? IDK the largest those shape packages get, like bigger then 1206, but would any of those inductors or caps get heavy enough to fall off ? I still mean little rectangular shaped, 2 pad parts, like some big current sense resistors or something.

I'm sure it depends some on temperature, the solder alloy, and amount too, and shape of pad and part.

[wraper]

Large inductors and radial capacitors likely will fall down. Polymer capacitors in rectangular package most likely will hold. Any BGA, BGA, LGA, QFN will hold.