PCB Milling reccomendations

[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.

[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]

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/4...0-cnc-kit.html

[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

[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.