PCB Milling reccomendations

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.

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.

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,

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.

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.

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.

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.

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.

Quote:

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Originally Posted by A_Camera

and for this, a CNC is the WRONG solution.

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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

Quote:

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Originally Posted by magicniner

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

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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.