Plated half hole PCBs fabrication & assembly
Rows of holes are drilled alongside the edge of a PCB to produce plated half hole PCBs. When the holes have been through plated, the edges are pruned so the holes along the boundary are reduced in half. The edge of the PCB will look like the top of a plated, half hole PCB.
Many times, it is used for the simple task of linking adjacent boards. They also may also be included as a part of the board circuitry such as accessing parts on a daughter board. An additional benefit of plated half holes is that it provides additional ways of connecting boards that are placed alongside the boundaries of the PCB, an area that is idle from the beginning. Plated half holes are primarily utilized in board-on-board connections, mainly when two circuit boards with dissimilar technologies need to be combined. It will look like the PCB has SMT pads at the base with vias in them and has been divided through the middle of the vias.
The board-on-board PCBs therefore need plated half-holes, which serve as SMD connection pads. Through directly connecting the PCBs together, the whole system is considerably thinner than a comparable connection with multi-pin connectors.
Design Advice
The milling tolerance is +/- 150µm
Distance pad to pad: min. 250µm
The milling gap within a panel needs to be 10mm min. (see drawing)
Use the largest hole diameter possible
Use the largest outer layer pad possible, both top and bottom sides
If possible, connect inner layer pads to the plated hole (brings more stability and helps to avoid burrs)
Plated half holes are economical connection techniques, which transform the board into a surface mount sub-assembly. They are frequently used as breakout circuits for fine-pitch SMD parts or on small radio or RF assemblies. Since they are plated and concave, these PCBs provide better landings for soldering. Their position on the boundaries of the board signifies that the surface mount part or daughter board will mount flush on the motherboard surface. There will be no space for dust or moisture to gather once the unit is in place.
Below is an example for reference
This plated half hole PCB(left) working as a sensor module.
The right PCB is the main board
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