Additional Custom Circuit Board Design Considerations

A figure such as 1.6 mm is used to indicate the thickness of a layer board. On 4 layer boards, 1.6 mm is the standard measure. Boards with greater thickness, for example, will offer more support when heavy connecting objects need to be supported.

The standard level of copper thickness on plane layers is 35 microns. Alternately, copper thickness is sometimes indicated in ounces or grams. It's best to go for higher than normal copper thickness on boards that support a lot of applications.

Tracks aren't meant to transfer power, but this can sometimes happen when signals don't properly handle frequencies. If the problem isn't kept in check, the tracks could end up losing major amounts of power. To get as much power as possible moved from one side of a track to the other, the layout of the track must account for transmission equations.

Generally, two inches is the right track distance on layer boards that consist of copper-tracked FR4 PCB material, providing that the signal time is one nanosecond. However, you must consider the effects of transmission line for high track lengths, particularly if signal integrity is crucial. The Internet is full of programs and spreadsheets that are designed to help people make proper impedance calculations for specific layer boards.

On most boards, vias are empty, and you can usually see right through them. Nonetheless, there are various circumstances under which vias can be filled. For starters, it's necessary for the vias to be filled when it comes to forming protective barriers from dust and other impurities. Secondly, vias might be filled to boost the carrying capacity of a current, in which case conducting materials might be used. Another reason that vias might be filled is to level a board.

Vias are typically filled with ball grid array (BGA) pieces. If contact occurs between a BGA pin and an inner layer, solder could slip through the via and onto a different layer. Therefore, the vias are filled to ensure solder doesn't leak to another layer, and the integrity of contacts are maintained as intended.

One of the more troublesome occurrences on a layer board is when a contact breaks in and out at some point along the board. The more this happens, the sooner that part of the custom circuit board design is liable to give out entirely. The average home electronics user will experience this problem when one of the buttons on a calculator stops working. Each button presses down on a particular part of a layer board, and when one spot gets faulty, the button that correlates to that spot cannot send its signal.

Another way contacts can be rubbed out in certain spots is when a secondary card slot is put onto a motherboard. If the card is poorly handled, one of the spots along the card could get damaged and fail to work from there on out. The best way to protect the surfaces of board that make contact with one another is with the use of a gold layer, which serves as a life-enhancing barrier. Gold can be costly, however, and its use in the tabs adds another step in the process of PCB fabrication.

Share this Post: