How do I order PCBs with countersink holes at JLCPCB?

JLCPCB offers countersink hole processing as an optional service for customers.Countersink holes, also known as recessed holes, funnel holes, or flare holes, are mainly used to allow screw heads to sit below the PCB surface, preventing raised screw heads from affecting the overall board thickness.

In PCB manufacturing, a countersink hole is first made by drilling a through-hole (PTH or NPTH), then using a conical drill bit to machine a recess to a controlled depth. Countersink holes are divided into two types:

1. Conical Countersink Hole: The screw head tapers from top to shank, so that once installed, the screw or bolt head sits flush with or below the PCB surface (currently, JLCPCB only supports this type).

2. Cylindrical Countersink Hole: The screw head is cylindrical and transitions directly to a smaller cylindrical shank (this type is not currently supported).

■ Process Description for Countersink Holes:

■ Factors Affecting Countersink Size:

Currently, JLCPCB processes only conical countersink holes. For larger through-hole diameters, deeper countersink depths, and larger angles, the resulting countersink diameter will also be larger.

■ Important Considerations for Countersink Holes:

1. Major Hole Diameter:

Must maintain a minimum clearance of 0.2 mm from surrounding pads, traces, and copper areas to avoid damaging them during machining.

2. Countersink Angle:

Must correspond to the screw shape to avoid mismatches and ensure safe clearance.

3. Countersink Depth:

Must be determined based on the total board thickness. The remaining thickness (total board thickness – countersink depth) must be greater than 0.2 mm to avoid weakening screw retention or causing failure.

4. Countersink Direction:

Must specify from which side the countersink is drilled to ensure proper screw installation.

5. Countersink Property:

Generally, the countersink inherits the same property as the through-hole. For example, if the through-hole is PTH, the countersink is also made as PTH; if the through-hole is NPTH, the countersink is also NPTH.

Tips:

1. JLCPCB can produce both PTH and NPTH countersink holes (normally, if the through-hole is PTH, the countersink is also made as PTH; if the through-hole is NPTH, the countersink is also NPTH).

2. When placing an order, besides filling major hole diameter, primary hole diameter, countersink angle, hole property and direction, a picture of the countersink hole location should also be attached.