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Knowledge is the key to identifying the small details that makes the big cost difference for your printed circuit board. There are many types of printed circuit boards and multiple choices between the development of schematic and BOM to PCB technology selection, electronic PCB design, mechanical and physical properties, and PCB specification.
Component Technology and BGA Size
The component size and technology have the most significant influence on the PCB cost. Most surface-mounted microchips can be designed into standard PCBs with plated through-holes. If the same microchip comes in a BGA package, it might need microvias and buried vias using a higher wiring density to be designed into an HDI PCB. Generally, PCBs containing BGAs become HDI PCBs when the ball center-to-center pitch is below 0.8 mm. If your physical board properties allow it and the component availability is equal, you should strive to find the BGA with the largest pitch to reduce the component and PCB cost.
For example, the same BGA microchip can be found with pitch 0.8 mm, 0.6 mm, and 0.5 mm. The 0.8 mm pitch BGA can be routed on an eight-layer standard PCB with a price index of 100. The 0.6 mm pitch can be routed on a (1-6-1) eight-layer, one-step HDI PCB with a price index of 200. The 0.5 mm pitch BGA can be routed on a (2-4B-2) eight-layer, three-step HDI PCB with a price index of 350. The number of lamination steps is the most significant cost driver for HDI and ultra HDI PCBs. Designs with BGAs equal to or less than 0.4 mm and multiple rows challenge the capability of HDI suppliers, which leads to the use of UHDI design parameters and thereby reduces the availability and increases the cost.
Material Selection
Correct material selection that complies with the performance and functionality of your application also plays a crucial role in the PCB cost.
The most common stackups of standard PCBs are specified with 35 µm Cu on all layers. The manufacturer starts on 17.5 µm Cu on outer layers and 35 µm Cu on inner layers, since the final outer layer Cu thickness reaches approximately 35 µm after plating. But 35 µm Cu on the inner layers isn’t always required and can be replaced by 17.5 µm for the current flowing in many electronic devices. This, in turn, lowers costs.
To continue reading this article, which originally published in the August 2024 Design007 Magazine, click here.
