What is a Bare PCB?
A bare PCB, also referred to blank PCB, is a type of printed circuit board that does not have any electronic components installed on it. These boards typically feature substrate, copper foil traces, solder mask, and silkscreen. However, in the absence of components, the bare board provides only electrical pathways and does not possess the required functionality as per the design. It needs to undergo subsequent processes such as soldering and assembly to become a complete circuit board, fulfilling its intended purposes.
Bare Board Testing
Before proceeding to assembly, it’s crucial to ensure the integrity of the electrical connections. Many shorts and disconnections may go undetected through simple visual inspection. So, to evaluate electrical connections on a bare board, two common methods for are the flying probe test and the fixture test.
The flying probe test utilizes removable probes equipped with drive devices to make contact with the test pads and vias on the board. This method is highly versatile as it does not require a dedicated fixture and can adapt to various PCB designs.
On the other hand, the fixture test, also known as In-circuit testing or Bed-of-Nails test, involves a dedicated test fixture equipped with hundreds of probes that precisely match the nets on the PCB. However, the fixture must be remade if any changes occur in the PCB designs, which can make it less flexible for prototype or low-volume production scenarios.
What is a Zero PCB?
As we talk about bare boards, there is a similar term called zero PCB that catches our attention. Zero PCB also called Perfboard or DOT PCB, is a type of board that is not designed for a specific application or function but is rather a versatile and generic board. Zero PCBs have small holes arranged in a grid pattern, each of which is electrically isolated from the others.
Zero PCBs are helpful in testing circuit designs for any shortcomings. They provide a cost-efficient way to evaluate the circuitry before committing to a final, unchangeable solution. The term ‘zero’ in the context signifies a fundamental distinction. It implies that there are no predefined connections, layouts, or functions on the PCB. Beyond that, ‘zero’ PCBs exhibit additional structural distinctiveness.
Copper Traces or Pads: Zero PCBs have a layer of copper traces or pads on the substrate. These copper elements provide the conductive pathways for soldering electronic components and forming connections. However, the copper traces on zero PCBs are usually unconnected, meaning there is no predefined circuit layout. You can build a circuit on them by inserting components into the holes and then connecting them with wires. It functions like a breadboard, providing a convenient platform for custom circuit creation.
No Solder Mask and Silkscreen: Zero PCBs typically lack both a solder mask and silkscreen, which are common features on standard PCBs. The primary objective of a zero PCB is to offer a blank canvas for users to create and test custom circuits. As a result, they are intentionally kept simple in structure to allow for maximum flexibility, customization, and experimentation. Users are free to design and solder their circuits and components directly onto the board without the constraints of a predefined layout or solder mask.
