how can i improve the milling of small pad especially for MCU like stm32750vbt6

That is very ambitious for a milled circuit board. You need a very fine bit. The height varies. The bottom left of the square IC is too deep and the top right is too shallow. There are devices that you can use on engravers to keep the depth constant, which might help.

https://www.2linc.com/product/control-engraving-depth-standard/#:~:text=The Depth Control Engraving System limits exposure of the Engraving,Size Spring Loaded Engraving Tools.

It is really very quick and cheap to get a printed circuit board made for prototypes, and that can have solder resist, through plated holes and even multiple layers. I've used JLCPCB and they are very good for that.

Diver300 said:

That is very ambitious for a milled circuit board. You need a very fine bit. The height varies. The bottom left of the square IC is too deep and the top right is too shallow. There are devices that you can use on engravers to keep the depth constant, which might help.

https://www.2linc.com/product/control-engraving-depth-standard/#:~:text=The Depth Control Engraving System limits exposure of the Engraving,Size Spring Loaded Engraving Tools.

It is really very quick and cheap to get a printed circuit board made for prototypes, and that can have solder resist, through plated holes and even multiple layers. I've use JLCPCB and they are very good for that.

Click to expand...

I agree, JLCPCB are excellent, cheap and fast - I use them all the time, at home as well as at work.

Inventer_muganza said:

View attachment 147495for example on this am using a spiral carbide engraving bit of 0.1mm 10 degree but some pad are well done but other copper are being removed how can i collect them

Click to expand...

You'll need one or more of the following...
- a better quality (flatter) board
- a better way to clamp the board to avoid cupping/bending of the board from flat
- a vacuum table that is extremely flat
- a gantry for your cnc with straight rails and essentially no flexing.
- no up/down movement of your shaft in the quill

Flatness over a large area is pretty difficult for a multilayer organic/inorganic multilayer. Any stress in the materials during fabrication of copper foil, epoxy resin, fiberglass mat, epoxy, fiberglass mat, epoxy, copper foil - your board will twist/warp with temperature changes (and it does and it may not even be flat from the beginning). If you have a single-sided copper board, you'll get even more warpage and unevenness.

Remember, you're only removing about 35 micrometers of copper so flatness must be better than the depth you are penetrating the epoxy resin below the copper.

Flatter board is partially taken care of by running probing correction routine, leveling,
and using that data to correct mill G Code. But as ZZO states problem has
additional problems not solved just by leveling code.

I gave up on milling years ago. I cannot hand solder the parts. There were solder shorts everywhere.
JLCPCB

I use flood and wick approach, so far ok.

We used to have a Pace SM soldering station where I worked, that had a special 'spoon' shaped bit (big no/no usually for soldering) - for large IC's as shown you simply brushed that part of the board with liquid flux, then filled the spoon with solder.

Next position the IC exactly and hold it in place, then simply draw the soldering bit along each line of pins in turn. It solders all the pins perfectly, without shorting any out - it was like magic

The trick of course is the liquid flux, and the 'spoon' to hold enough solder.

With a small enough tip, fine diameter solder and high enough temperature iron, and steady hand, it becomes pretty easy to solder by hand - especially if you extend the length of pads to allow the iron to heat the exposed section of the pad.

Magnifying glasses also help.