Cost Determining Factors When Quoting PCBs – Part II
Our last post covered many of the cost factors used by a fabricator to calculate cost of a printed circuit board. For those with industry experience many of these factors may be obvious but there are other factors that contribute to cost that may be less obvious and we’ll cover several of these today. Having an understanding of these cost factors will not only empower buyers to ask the right questions of their fabricator but will also enable designers to design with optimal performance and cost efficiency.
Tooling and Test Charges
Tooling costs may include cost for CAM time, film costs, etc. There are a variety of tests that can be performed related to manufacturing a printed circuit board. An Electrical Test would be the most common, which will do a basic open and shorts test of the PCB to make sure it is electrically sound. Additional tests are typically done by customer request and include TDR for Impedance Testing, Ionic Testing, etc. The specific costs related to these items vary greatly by manufacturer.
The most common finish type is still a lead finish called Hot Air Solder Leveled (referred to as HASL). There are a variety of other finishes, silver finish options, several gold finish options (ENIG, body gold, gold fingers, etc.) and more. These non-standard finishes can add 10% to 20% or more to the cost of the project.
Our last post discussed mechanical drill costs. If much smaller holes are required – often referred to as microvias – then a laser drill process is required. Use of a laser drill can add significant costs to the overall process. Another cost factor to consider are blind or buried vias; vias that do not go all the way through the entire board. Each additional drill process can add as much as 20% or more to the overall board cost.
Processing a multi-layer printed circuit board that requires something outside the standard process can add costs. For example, a process that includes sequential lamination or laminating FR4 with a different material type such as polyimide.
IPC Class 2 is a common standard for final printed circuit board inspection and quality processes. Class 3 is an upgrade from Class 2 that requires additional processes such as coupons and cross-sections to be added to the manufacturing process. Those customers who require a higher degree of quality assurance may want to consider requesting a Class 3 process but should also expect a 15% to 20% increase in project cost.
Vias on a PCB are usually not filled completely. They will have copper plating and finish in the holes but they will not be completely filled. However, vias can be filled, if required, with either non-conductive or conductive material. This process will add 10% or more to the cost of the PCB.
Additional costs will be incurred when there is additional fabrication that needs to be done to the finished board. These include things like counterbores, countersinks, complex routing, controlled depth drilling etc. These costs vary greatly depending on what is required.
These are many of the primary and secondary variables a fabricator uses when preparing a price quotation for a customer. Of course, for a customer, the price of a printed circuit board is not always a measurement of the true costs in the manufacturing process. Delays in delivery by the fabricator or a board failure because of an inferior manufacturing process can cause the real price to be much higher.
So, when quoting your next printed circuit board project, be sure to clearly identify your project requirements, ask the right questions of your fabricator and design for optimal performance and price efficiency.