In the PCB manufacturing process, special process holes are mainly used to meet specific functional requirements. Here are some common special process holes:
Blind Via:
Characteristics: Connects the surface layer of the PCB to an internal layer without passing through the entire PCB.
Application: Commonly used in high-density interconnect (HDI) designs.
Buried Via:
Characteristics: Fully located within the internal layers of the PCB, without extending to the surface.
Application: Used to connect different internal layers of the PCB.
Micro Via:
Characteristics: Very small hole diameter, typically smaller than 0.15mm.
Application: Mainly used in HDI PCBs to reduce PCB area and enhance signal transmission speed.
Through-hole Via:
Characteristics: Passes through the entire thickness of the PCB, extending from the top copper layer to the bottom copper layer.
Application: Used for connections between signal layers and also for power and ground layers.
Gold Finger:
Characteristics: Gold-plated columns on the PCB edge to enhance conductivity and wear resistance.
Application: Commonly used for connecting PCBs to computer motherboards or other devices.
Impedance-Controlled Hole:
Characteristics: Designed with precise hole size and location to control impedance.
Application: Used in high-speed circuit designs to ensure signal integrity.
Non-circular Hole:
Characteristics: Holes that are not round, such as elliptical, diamond, or square.
Application: Used for securing and interconnecting special components.
Control Depth Hole:
Characteristics: A groove with a specific depth.
Application: Used to secure heat sinks, connectors, or other components that require precise depth control.
Half-hole/Edge Plating Process:
Characteristics: A partially through-hole formed at the edge of the PCB, with an additional copper layer to enhance the connection strength.
Application: Used in edge connectors and special interface designs.
Nickel Gold Plating and Electroless Nickel Palladium Gold:
Characteristics: A uniform, fine, and strongly adhesive coating formed by electroplating.
Application: Increases PCB hardness and wear resistance, effectively preventing diffusion of copper and other metals.
Press Fit Hole:
Characteristics: The metal inside the hole is compressed to form a certain contact force.
Application: Used for connecting electronic components with PCB pins.
Countersink/Counterbore Hole:
Characteristics: The bottom of the hole is flush with the board surface, with a circular or flat-head shape.
Application: Used in PCBs that mount surface-mount components.
Counterbored Hole:
Characteristics: The hole gradually widens inside, resembling a trumpet shape.
Application: Used for signal transmission between circuit layers with higher density connections.
These special process holes play an important role in the design and manufacture of electronic products, meeting the requirements of various levels and fields of electronic devices.
For any type of counterbore hole, the main through-hole must be drilled first. Then, based on the shape of the counterbore, different tools are used for counterbore processing. Flat-bottom counterbores require milling with an end mill after drilling, while tapered counterbores need a larger drill bit to perform reaming. During counterbore processing, it is important to ensure the workpiece is positioned correctly to maintain concentricity between the hole and the counterbore.