Countersink Hole is used in PCB board that sink the screw head into PCB laminate.so that the board looks clean and flat.countersink hole generally have two types of shapes.V figure Count-sink and T figure Count-Sink.
When you plan to design countersink in your board, below information is required:
- Which side of countersink hole be drilled? Like Bottom Layer?
- Is the countersink hole plated or non-plated?
- What is countersink hole diameter(d2)?
- What is through hole diameter(d1)?
- What is the depth of countersink hole need to sink(t1)?
- What is angle of countersink hole(like 90 degree or other)?
The CAM file of countersink hole:
1.Editing of routing layer:
It is important to know the depth of countersink hole,it will be drilled into the layer which need be cut copper at inner and outer layers for NPTH,and whether it affects electrical performance for PTH.Usually the depth tolerance also need to be taken into account when calculating depth of countersink hole.
For example: NPTH countersink hole need to be drilled from top layer to the fourth layer, then the L1-L4 must be according to countersink hole without leakage copper and cutting copper to make at inner and outer layer. Such as hole diameter is 4.5mm, the inner layer does not leak copper with cutting copper 0.2mm, so that the inner hole corresponding to the overall size of the cutting copper should be 4.9mm.
2. Editing of solder mask layer
If it is NPTH, the welding window shall be opened at least according to the NPTH hole corresponding to the countersink hole.If it is PTH, the welding window shall be opened properly according to the outer layer of the countersink hole.If the customer does not design the mask window, it is necessary to confirm the normal window opening according to the welding pad.
For example: 4.5mm NPTH countersink hole,be drilled from top layer,if the normal NPTH hole welding resistance window is larger than the hole with 3mil, then the corresponding countersink hole top layer welding resistance window is 4.5mm+0.15mm=4.65mm.
3. Countersink hole files output notice
When the countersink hole is drilled at bottom layer, the drill hole output must be mirrored.
4. Process instruction
PTH countersink hole is usually done by after standard drilling.
NPTH countersink hole is usually placed in front of the milling process.