PCB Milling reccomendations

[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/4...0-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?? ��