Advice for a new BGA rework station owner please

[diif]

Re: Advice for a new BGA rework station owner please

I use a universal stencil (1mm pitch 6mm balls) often. It's larger than the LG processor and there is a square inside with no balls. I just place a large piece of kaptop tape over the stencil then cut away with a scalpel where I want the balls. Takes a lot less time than an an hour and it's less fiddly than trying to remove balls.

Clean room wipes are better than cotton pads as they are lint free.

[dicky96]

Re: Advice for a new BGA rework station owner please

Can't I also use specific (made for a particular BGA) 80mm or 90mm stencils with that same universal station that diif posted?

I get the idea to have some universal stencils for when i don't have the specific one and don't want to wait a month

I have a bottle of Topnik TK83 flux that I never used much. Is that any use for this sort of work?

[diif]

Re: Advice for a new BGA rework station owner please

Yes, it holds any stencil 80 or 90mm, universal or specific.

Tacky flux is advised to hold the balls in place.

[dicky96]

Re: Advice for a new BGA rework station owner please

OK, thanks diif. I like your idea of using kapton tape and cutting it to make a specific stencil from a universal one, while I am waiting for specific ones to arrive.

Including 10 universal stencils and 10x solder balls, does this kit contain everything I would want to get started? It's a bit unclear, what they call 'solder paste' looks like flux to me in the pics.


https://www.aliexpress.com/item/3304...chweb201603_55

I will get the £30 Amtech flux you first advised.

One other question - would that reball station hold a LGA socket, should I want to reball one? I can get 90mm stencils for various LGA.

[diif]

Re: Advice for a new BGA rework station owner please

Yes, that's flux not solder paste, it should get you started yes. I initially had a much simpler holder but it only held square chips and it wasn't so easy to adjust the height of the stencil above it.

I've got an 1156 socket here to test with and whilst it's held firmly by the clamps, it's too tall and sits just a little too high for the stencil to sit just above it.

Decent braid is a must if you don't already have some, I use Chemtronics.

[dicky96]

Re: Advice for a new BGA rework station owner please

OK I ordered that kit.

Actually I suppose replacement LGA sockets are pretty cheap anyway so maybe it's not even worth the effort of reballing them. I have a few motherboards lying around with problems such as can't detect RAM or cant' detect PCIe graphics card, and I've not managed to fix those ones.

I was just wondering how many of those may actually have problems with bad connections on the CPU socket (not bent pins) or North bridge.

[dicky96]

Re: Advice for a new BGA rework station owner please

I got the Amtech Flux

I also got some Mechanics XG50 Solder paste, as I fancied trying some because I've not used paste before with SMD

This is getting to be quite a shopping list lol but I think I may have what I need now to get going

The Rework Station is one it's way now - I have tracking number and it should be here about 5-7 days time. I do hope that does not turn out to be a POS, like m4a2t0t thinks!!

[diif]

Re: Advice for a new BGA rework station owner please

There was/is a user from here that use to reball using a toaster oven element for the bottom heater and hot air for the top.
He upgraded to a 3 zone machine similar to yours but with out the auto bit.
I doubt the one you've bought is a POS.

[dicky96]

Re: Advice for a new BGA rework station owner please

I've had the G720 for a few days now and I've been practicing a lot on scrap boards both with unsoldering BGA and QFP and also resoldering QFP

I haven't tried reballing BGAs yet but my reballing clamp/station and stencils arrived Monday so that's next.

I have to say that this machine is a dream to work with. The initial problem I had with profiles was my own stupid fault - there are switches at the side of the machine for the IR heaters (2 switches, for left and right heater) and I had them switched off!


It's now unsoldering BGA and QFP reliably, though i have one BGA that failed to desolder yesterday and I need to check if that is glued to the PCB. If it is then how do I deal with it?

I've tried the optical alignment on a large QFP and it took me several attempts before I could get it to align properly. The first problem was that the QFP and the PCB pads were showing different sizes. After asking for some advice I was told to read the manual page 17 again!

It turned out that the joystick which zooms in and out also raises or lowers the QFP so you can get the size of the QFP in the camera to match properly with the PCB pads - but you have to select 'manual mode' on the touch screen before the joystick will actually control the up and down position of the top nozzle which is holding the chip by suction. The joystick controls the zoom anyway without selecting manual mode. This was not mentioned in the manual but I eventually figured it out by pressing buttons until it worked lol

Also getting the brightness of the QFP and PCB illumination set correct is important otherwise the image can be a bit blurry and chip can look like it is aligned correctly but it isn't. Once again a few trial and error attempts got that sorted.

The upshot of all this is that I ended up desoldering, aligning and resoldering the same QFP about 7 or 8 times until I got it right. However during all that rework the machine never lifted a pad and the PCB has not warped or burnt - see attached pic taken after 7 or 8 reworks

I think I have pretty much mastered this machine, and considering I only had 3 half days to really practice with it and I've never used a BGA station before, I think that is pretty good going and probably says more about the quality and design of G720 and the pre-programmed profiles than it does about my abilities!

So it seems the machine is not going to lift pads or warp PCBs but the problem I am having at the moment is lifting pads when cleaning the PCB once I removed the chip

On that QFP photo you may see that one pad is missing. That lifted when I tried to clean up the PCB the first time I removed the chip. All the other times I just resoldered with the existing solder, I didn't even add new flux though in reality I would do. I was trying to learn the alignment system rather than get good shiny solder joints

So.... Any advice on how not to lift pads when cleaning the PCB would be appreciated. I need to get that right.

I currently have my soldering station on 320C. Is that OK? I'm using Servisol braid dipped in Pasta de Lutovania Rosin. I'm cleaning afterwards with Isopropyl and a brush simialr to a toothbrush

Also how to deal with BGA that are glued to the board?

[diif]

Re: Advice for a new BGA rework station owner please

As mentioned in the other thread, push a leaded ball of solder around the pads ideally without touching them and wait for your Chemtronics braid to arrive. If that Servisol is the same as the stuff I have you will notice a massive difference.

Hot air and a tooth pic to chip away at glue if it's on the corners.

[dicky96]

Re: Advice for a new BGA rework station owner please

Thanks, I've been practicing that solder ball technique.

The Chemtronics I ordered to the UK as I'm going back for a few days over xmas so I will bring it back with me.

I had a go at reballing, I had to find a video to see how to use that magnetic reballing jig.

I used a standard 0.76mm stencil and used some kapton tape as suggested to create a custom stencil for my chip

All went rather well, and here's me thinking this is easier than I expeced. until I tried to melt the solder balls with my 858D on lowest air settings, and the tacky flux liquidised and lost it's tackyness so some of balls in one corner of the BGA moved around and clumped together.

Not to be deterred I removed the heat and I tried to manually place the balls back where they should go and this time used the Kada 853B with a metal plate (lid off an old satellite receiver) placed over the preheater and the BGA on top of that and heated it from below - then gave it a final heating from the 858D held above.

it worked OK...ish.... from a beginners point of view but I ended up with one pad lost and one donkey's bollock of a solder ball on the adjacent pin. I'm not too disheartened by this - it's gonna take a bit of practice, I'm sure, and maybe some different flux. I'm using the tube of NC-218 that came with the reballing kit. The Amtech NC-559 isn't here yet

Still I thought I would mention all that and give you all a laugh - see pics

I then decided to have a look at that BGA that seemed to be glued down. I couldn't see any glue so decided to give it a good go with the Kada 853B and the 858D to see if I could get it off and find out what was under there

With a LOT of heat I eventually got it to come loose (though it seemed stuck towards on side) and I removed the chip - less quite a few pads all in one area (see other pics)

It is much finer pitch than the BGAs I have removed so far. Maybe that is the problem. Probably I need to program a hotter profile for some BGA chips - but I think I've broken more than enough stuff for one day so I'm gonna leave it at that for now and start afresh tomorrow

[diif]

Re: Advice for a new BGA rework station owner please

You're mixing indirect heating stencils with direct heat, I'm surprised there aren't more big solder balls.

[dicky96]

Re: Advice for a new BGA rework station owner please

Probably......... as I am not sure what the difference is, but I'm determined to learn. It was my first attempt

Watched another video today that suggests what I did would have worked but for the fact I had too much flux on the BGA

Time to try again tomorrow

Also gotta find another BGA that the G720 will not remove - then i can mess around with profiles. I've got plenty of scrap PCBs to play with so hopefully I will find another good candidate

[dicky96]

Re: Advice for a new BGA rework station owner please

Reball attempt No 2. The main difference is I used a much thinner layer of flux.

No donkeys bollocks this time but I somehow got two balls with a solder bridge, even though they are correctly positioned on the pads,. See pics. Is that game over start again or can it be corrected?

Most of the balls are the same size this time though some look slightly larger than others

Also some of the balls are shiny but some seem to have collapsed in on themselves somehow and had a dimpled appearance

Is this normal, is this bad technique on my part or bad quality equipment (flux, balls)?

I read or saw a video somewhere that says if you rub the reballed BGA against a bit of paper it will level out all the balls so the BGA sits properly when it is resoldered to the PCB. is that good advice? I tried it on the BGA and I can see that some of the slightly larger balls have a flattened bottom now where the paper has rubbed them

I found that using the Kada 853B with a small metal plate and a thermocouple attached to it is a pretty good way to melt the balls without them blowing around, then once they melt I give them a quick going over with my hot air station to be sure before turning the Kada 853B to cooling mode.. Is that good technique?

Rich

[dicky96]

Re: Advice for a new BGA rework station owner please

As mentioned in the other thread, push a leaded ball of solder around the pads ideally without touching them and wait for your Chemtronics braid to arrive. If that Servisol is the same as the stuff I have you will notice a massive difference.

Hot air and a tooth pic to chip away at glue if it's on the corners.

Hey diif, I got the Chemtronics braid a few weeks ago but I was busy so didn't have time to try it

I had a play around with that today - I removed a BD82H61 BGA from a scrap LGA 1155 motherboard and then used the Chemtronics braid with Mechanix UV50 flux to clean everything up

https://www.aliexpress.com/item/3300...1e444c4dA70TjY

I have to say the Chemtronics braid was a really good recommendation from you. I had no problem cleaning up both BGA and PCB without any damage.

I'll definitely order some more of that braid now, I just got 2x 1.5m to test with but I suspect I will be using quite a bit of it.

[diif]

Re: Advice for a new BGA rework station owner please

I'm glad you like it.

[sam_sam_sam]

Re: Advice for a new BGA rework station owner please

Is this any good

MECHANIC 40G Solder Wire 0.2mm 0.3mm 0.4mm 0.5mm 0.6mm Tin Lead Rosin Core For Phone Circuit Board Welding Line Reel

https://www.aliexpress.com/item/3301...6-437668149de4

[diif]

Re: Advice for a new BGA rework station owner please

Is this any good

MECHANIC 40G Solder Wire 0.2mm 0.3mm 0.4mm 0.5mm 0.6mm Tin Lead Rosin Core For Phone Circuit Board Welding Line Reel

https://www.aliexpress.com/item/3301...6-437668149de4

No idea, I have ordered a roll though, I only have 07mm pitch currently.

[sam_sam_sam]

Re: Advice for a new BGA rework station owner please

No idea, I have ordered a roll though, I only have 07mm pitch currently.

Let us know what you think of it when you use it

[dicky96]

Re: Advice for a new BGA rework station owner please

Funnily enough I ordered a roll of the same? Mechanic 0.2mm from Aliexpress as I also only had 0.7mm 60/40

https://www.aliexpress.com/item/3287...684c4c4d8l8HzV

It arrived on Thursday, I'm hoping to have time to try it tomorrow on some 0.5mm QFP chips to practice.

I'll let you know