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[Moved] About Some Unusual PCB Features in PCB Design


Newbie level 4
Mar 23, 2020
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I am here to share some unusual PCB features encountered in previous pcb production.These may help Makers use your imagination in PCB design.

PTH on the Edge
It is also called “castellated holes”. These are plated holes cut through on the board edge and used to join two PCBs either by direct soldering or via a connector. During the production, it is necessary to pre-process the semi-hole position before etching circuit to make sure the semi-hole position is smooth and no burr.

Process capability:
The hole diameter on the edge is minimum 0.6MM, and the half hole should be drilled inside the boards ≥0.3MM

The spacing between castellated holes should be greater than 0.55MM, or it will easily cause short circuit.

Edge Plating
This means that most or part of the edge of a PCB or a cut-out is plated from the top side to the bottom side. This may be to ensure a good ground to a metal casing or for shielding purposes. To manufacture a board with round-edge plating we rout the board profile where the edge plating is required before the through-hole plating process.

1.The edge plating location required at least 0.2MM circuit pad, or the copper will be easily peel off.
2. As we need to hold the circuit within the production panel during processing we cannot plate round 100% of the edge. There must be some gaps (at least three gaps) so that we can place rout tabs.

A countersink is a cone shaped hole cut into the laminate. It is typically used to allow the tapered head of a screw to sit flush with the top of the laminate. By comparison, a counterbore makes a flat-bottomed hole and its sides are drilled straight down. This is usually used to fit a hex-headed cap or screw.

To accurately drill your countersunk holes, we will need the following information.
1. Angle of the drill
2. Major Diameter (finished diameter of the hole at the surface)
3. Depth the countersink is to be drilled
4. On which side of the board is the sink? Top or Bottom?
5. The finished diameter of the shaft of the hole
6. Is the sink and shaft to be plated or non-plated?

Process capability:
The depth tolerance of the countersink hole is +/-0.15mm.

1.Countersunk-head screws that follow the ISO standard very often have a 90° angle, if you require the other angle, we need to purchase the drilling tool.
2. The data of countersink hole is mutually restricted, so if you are changing one data, you should change the others accordingly.

Depth Routing
Normally all routing done on a PCB is going through the whole board thickness. PCB Depth control routing technology is the stepstair or groove shaped by partial routing in printed circuit boards(PCBs) manufaturing.It have great advantages in PCB assembly as the special shape of depth routing.

Process capability:
The depth tolerance is +/-0.15MM; the minimum depth is 0.3 +/-0.15MM; the minimum balance thickness is 0.4+/-0.15MM

Press-fit holes
Press-fit holes are used as PTH holes to fit the leads of connectors that will not be soldered but pressed into the holes. The hole tolerance is tighter than the standard +/-0.10mm, usually it is +/-0.05mm, so even required +/-0.025mm.

Process capability:
The tolerance of press-fit holes we can control is +/-0.05MM

If you are interested in these, you can contact me and discuss.We are a Professional PCB&PCBA manufacturer:King Credie Technology Limited.

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