3 PCB Manufacturing Constraints That Engineers Need to Know

Electronics production

Communication is key when constructing a product as complex as a printed circuit board. Custom PCB manufacturing requires lots of planning by both the PCB fabricator and the engineer that designs the PCB prototype.

Since miscommunication is likely between these two parties, severe consequences in the manufacturing process can occur. Here are three big problems that can occur when planning is not thorough:

Clearance Issues: Lack of communication with an engineer can cause design issues that affect the assembly of each circuit board. Manufacturers have “clearance constraints,” that they must maintain between each layer of the circuit board. Often, an engineer will design a board below the minimum clearance constraint, and the manufacturer is incapable of producing a PCB with such a small constraint. Outlining manufacturing capabilities and having an in-depth meeting with the designing engineer on the project will eliminate this type of problem.

Controlled Impedance Calculations: A controlled impedance used to slow down an electrical circuit in order to allow certain connections to perform before others within the circuit. One example of a controlled impedance is the coaxial cable that connects the antenna to a television. They are made up of inner conductors and an outer conductor, or shield. The dimensions of the conductors must be controlled in accordance with the strength and shape of the electrical field. This determines the impedance of the circuit. FPGAs, processors, RAMS, and flashes all require impedance controlled tracks to maintain a strict order in functionality. Meetings between designers and manufacturers are necessary to discuss these specifications.

Drill Constraints: Similarly to clearance, PCB fabricators also have drill constraints that limit the size of the drill. Exceeding the limit set by the manufacturer can increase cost of production drastically. A typical drill size lies between six and 14 millimeters, obviously dependent on the PCB’s size. The drill holes depend on the size of the connecting pin used. PCB fabricators and engineers must be in close communication during every single manufacturing project in order to ensure a consistently high-quality, flawless end product.

Prior to designing the custom PCB, it is necessary for an engineer to consult the PCB manufacturer to make sure that all of these constraints have been outlined. If the engineer does not have this information and designs an impossible circuit board, then the manufacturer wastes time and money.

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