PCB Milling reccomendations

[PEU]

Good morning CNCUK members,

I am looking for some recommendations for a "budget" machine, firstly I will explain what it is I intend to use it for and hopefully someone will be able to guide me as to what will be suitable.

My line of work has led us to explore the possibilities of milling through a PCB (Printed circuit board) in order to access an hopefully undamaged EMMC chip from a mobile phone/tablet.
Our current method is to point a hot air gun at the chip until the solder balls underneath melt and the chip comes loose, we then have to "clean" the chip by scraping the remaining solder flat from the chip under a microscope. As you can imagine, the initial heating and scraping can damage the chip so we are hoping that milling through the board to the chip will provide a much more consistent method.

requirements:
anything milled will likely be smaller than an a5 piece of paper.
I believe we would also like to use the machine for other applications (4 axis if possible?)
materials to mill - Metal, PCB, plastic
precision/ depth accuracy - extremely important
Budget - £1500 inc shipping

I understand our budget is really quite low and I have attempted to do a fair amount of research but I am worried to order one of the £1200 milling machines from china just for it to be useless for us...

If there is anyone interested in what I have described and already own a milling machine that may fit the criteria and wouldn't mind having a visitor or two to test the theory, that would be extremely beneficial to us. (south of the UK/ Hampshire)

Thank you for taking the time to read and respond.

Edit* We want to mill through the PCB to expose an undamaged chip.

[A_Camera]

I am not sure it is clear to me what you want to do with it. Do you want to remove chips without damaging the PCB and the chip? Or do you want to cut through the PCB? Chips are normally removed through desoldering.

Anyway, a machine which matches your requirements will not fit your budget.

[PEU]

Apologies, we want to cut through the pcb to get to the chip so that the chip is undamaged.

As for it not matching our budget, I have seen people posting about building CNC machines would this be something we were able to do within the budget?

Thanks,

[Fred]

I'd have thought that hot air desoldering would be better than milling.

If you do want to experiment on the cheap, why not try a tiny mill like the Proxxon MF70 - manually first rather than CNC. You can get one (manual) for less than £300. A reasonably cheap way to prove your existing method is superior.

[PEU]

Certain phones have a very large and annoying amount of epoxy over/around the chip, to deal with this we have to heat the board to around 320/400+ Degrees Celcius. This is normally the stage in which damage occurs, we have contacts whom have successfully milled through the boards to expose the chips however that is with a £50,000 machine... far from our budget!

I will look into the manual option you have recommended, thank you.

[Fred]

That higher temperature would certainly make a difference. I also wondered what would hold the chip in place once you'd milled the board away.

[A_Camera]

Sorry, but this project sound crazy to me. You want to remove the soldered chip undamaged, and that is not going to work with a mill, regardless of budget. The only way you can do this is by using the proper tool, which is hot air desoldering. Using the proper tool for the task is always the best solution, and for this, a CNC is the WRONG solution. If you use the right equipment (not just any hot air blower) you don't need to scrap anything under microscope and will result in a clean surface. If you use a CNC you will just make a mess and definitely destroy the chip.

Feel free to build one, or spend the whole £1500 budgeted for this to find out on your own if you don't believe me, but for that money you can buy the tool for the task also (and that won't be a CNC). It's your choice.

[PEU]

It is not that I do not believe you A_Camera, just that we are aware that milling is an option because it has had much higher success rates than applying high temperatures to the chip. There are plenty of other methods to explore using rework stations with infra-red back heating etc however this served as an enquiry into "budget" options. I appreciate the responses and it looks like we will not be headed down the milling route for now.

[magicniner]

and for this, a CNC is the WRONG solution.

Always with the negative waves Moriarty! ;-)
Milling away the board from the back actually makes perfect sense if you read the bit about epoxy in his description of why heat isn't best for this!
A manual micro-mill like the Proxxon suggested above would be a logical first step, you would need to stabilise the chip (hot glue & a fixture?) to stop it lifting into the tool path close to the end of machining and if it suits your application you could probably then CNC it and still stay within your budget.

- Nick

[PEU]

Always with the negative waves Moriarty! ;-)
Milling away the board from the back actually makes perfect sense if you read the bit about epoxy in his description of why heat isn't best for this!
A manual micro-mill like the Proxxon suggested above would be a logical first step, you would need to stabilise the chip (hot glue & a fixture?) to stop it lifting into the tool path close to the end of machining and if it suits your application you could probably then CNC it and still stay within your budget.

- Nick

This is the attitude that I like to hear! I have discussed a hand mill with colleagues and due to the parameters that we would have to work with wouldn't be an option, nobody here would trust themselves eyeballing the depth going through the PCB.

As for holding the chip in place as we will be destroying the board regardless, I am thinking of cutting the chip out from the board so it will sit flat on its back and some sort of adhesive to hold it down.

You mentioned about being able to CNC it within budget, would this be with the chinese cnc machines found on ebay?

Thanks for the reply.

[A_Camera]

This is the attitude that I like to hear! I have discussed a hand mill with colleagues and due to the parameters that we would have to work with wouldn't be an option, nobody here would trust themselves eyeballing the depth going through the PCB.

As for holding the chip in place as we will be destroying the board regardless, I am thinking of cutting the chip out from the board so it will sit flat on its back and some sort of adhesive to hold it down.

You mentioned about being able to CNC it within budget, would this be with the chinese cnc machines found on ebay?

Thanks for the reply.

Grate! Good luck.

[magicniner]

This is the attitude that I like to hear! I have discussed a hand mill with colleagues and due to the parameters that we would have to work with wouldn't be an option, nobody here would trust themselves eyeballing the depth going through the PCB.

You don't eyeball, you fit a DRO to the Z axis (digital caliper bodged on is popular) and measure the PCB thickness, set zero for the lower surface and you're good to go for precision depth milling ;-)


You mentioned about being able to CNC it within budget, would this be with the chinese cnc machines found on ebay?

Crikey No! They're Shite! If the Proxxon does the job manually just add steppers, drivers etc.
To cut down on leg work you could look for something like -

http://www.robotpark.com/Robotpark-MF-70-CNC-Kit

Not saying that one is any good but read reviews and Google around a bit and preferably find a supplier you can visit if things are going particularly Pete Tong ;-)

ATB,
Nick

[magicniner]

Grate! Good luck.

Sound advice as always :D

[m_c]

Trying it manually first would be my suggestion as well.

The hardest part will be finding the balance between mounting the chip/pcb securely, and how much of a cut you can take without the chip/pcb moving. I'm sure you don't need anybody to mention that you'll most likely want to experiment on some already scrapped items.

The only benefit you'll get from CNC is being able to set it up and leave it to do the bulk of the work, as you'll most likely need to adjust the depth slightly to get within the required tolerances for the final cut(s).

To go with Nick's conversion kit suggestion above, I'm sure I came across a german supplier of kits a while back, but my google skills are failing to find anything. They did however turn up this Danish supplier kit - http://cnchobby.dk/en/cnc-machines/406-proxxon-mf-70-cnc-kit.html

[PEU]

Thank you very much, I will be speaking with my supervisor about getting the manual machine ordered with some callipers!

[PaisleyPCdoctor]

I work with PCB'S and BGA's every day and I don't see why it wouldn't work. Biggest risk is ripping a solder ball off along with the on chip BGA pad. Slow plunge and a bit of care and it should be OK.

As for Chinese CNC not being up to it? What? Of course they would! It's just milling a bit of pcb and copper.

In fact- why do you need a CNC at all? For 10% of your budget you could get a basic manual mill/drill press. With micrometer depth adjustment, just step down, move it around xy axes, then down a bit more. Again- you don't need cnc for this- basically you just need control of the z (plunge) depth.

Want me to remove a BGA through the PCB? I can post a video to let you see how it goes.
I use a China 6040 that I've owned for 2 weeks and I KNOW it can be easily done.

Edit... Obviously the pcb will be destroyed, but as I understand it- you just want to salvage the usable chip, right?

[PaisleyPCdoctor]

... we then have to "clean" the chip by scraping the remaining solder flat from the chip under a microscope.


Wait, what??
When you remove the BGA chip, you are supposed to remove the remaining solder using solder wick and flux. Then reballing with fresh solder balls. Why on earth are you scraping it?

[magicniner]

As for Chinese CNC not being up to it? What? Of course they would! It's just milling a bit of pcb and copper.

Go on mate, explain to me just how good they are, and how you'll fix yours :D

[PaisleyPCdoctor]

Removing a BGA chip is almost always best done with properly profiled hot air rework. When the solder balls melt. Lift the chip off. However, the chips the OP is talking about have been flooded aroundand underneath with epoxy (flooded around solder balls). By the time the heat has broken down the epoxy, the chips goosed.

Milling the chip away is totally doable. There are plenty of videos out there of it being done WITH CHINESE CNC MACHINES. It stands to reason that the process is virtually identical milling through the pcb from the other side (to salvage a working chip).

Will deffo want dust extracted milling either direction.

[PaisleyPCdoctor]

Go on mate, explain to me just how good they are, and how you'll fix yours :D

You what?? ��

[cropwell]

You don't eyeball, you fit a DRO to the Z axis (digital caliper bodged on is popular) and measure the PCB thickness, set zero for the lower surface and you're good to go for precision depth milling ;-)



Crikey No! They're Shite! If the Proxxon does the job manually just add steppers, drivers etc.
To cut down on leg work you could look for something like -

http://www.robotpark.com/Robotpark-MF-70-CNC-Kit

Not saying that one is any good but read reviews and Google around a bit and preferably find a supplier you can visit if things are going particularly Pete Tong ;-)

ATB,
Nick

Good grief ! that's cheap.