A good detective is always able to detect details that seem completely unremarkable. A small problem that goes unnoticed by others can be a clue to solving a mystery. Similarly, certain holes may seem insignificant in PCB design, but without these “tool holes,” the board would not function as intended, or even be manufactured correctly.
Individually, tool holes on a circuit board look ordinary because they are regular-looking through holes drilled into the circuit board. Only by studying their functions carefully can we truly understand their importance. Some of these holes are used to connect the hardware to the circuit board, while others are used to assist in the fabrication and assembly of the circuit board. In the design and manufacture of PCB, it is common to drill many holes of different sizes into the board, and these holes will be suitable for different functions.
Most of the holes are used to interconnect electrical signals between the layers, while some holes are used to solder components and to install different hardware.
The tool holes (also known as “mounting holes”) used to connect hardware can be associated with the component’s packaging pattern or can be labeled separately.
In addition to having leads or pins soldered to the board, some components have mounting hardware for added physical support.
Connectors are usually bolted to the plates to protect their welded parts from the pressure of cable plugging and pulling.
Other heavy or connector components may also be tightened, including switches, fans, batteries, and speakers.
These holes may also require the installation hardware to be connected to electrical ground or to conduct heat through the plate to disperse over the internal plane layer.
Finally, in order to install a PCB into its system, isolation holes are usually used to connect the hardware or bracket that needs to be installed to the board.
PCB tool holes can be placed on the board to facilitate different manufacturing stages.
These holes guide the board through its assembly processes, such as reflow soldering, wave soldering, and automatic optical inspection (AOI).
If the PCB requires additional testing, tool holes will also be used during testing.
If tool holes are required on the board during any manufacturing process, the manufacturer will require them to be added to the design.
Typically, the manufacturer will use the holes already on the board or add them to the manufacturing document.
The holes are created to install the hardware and must be machined with the correct design parameters to perform the intended function.
In addition to the different PCB tool holes needed to install hardware and production AIDS, the design needs to be aware of design issues that may affect PCB manufacturing.
These include solder paste pads for surface-mounted component pins, solder resistance film for protection of circuit boards and screen printing marks for component reference marks, as well as corporate logos.
In addition, the designer should also pay attention to the reference pad problem.
These are small pads used for PCB alignment during automatic assembly.
The reference pads are usually placed at the corners and centers of large SMT devices with high pin counts.
It can be challenging for designers to meet all the requirements required for PCB manufacturing and assembly.
But this is exactly what a good PCB design engineer should do.
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