Issue link: https://iconnect007.uberflip.com/i/978458
MAY 2018 I PCB007 MAGAZINE 33 global standardization on the roughness of copper foil, so the same category can have different degrees of roughness on the same type. Important also to know is that the fin- ished roughness may be changed during PCB manufacturing due to oxide treatment or ox- ide replacement chemistries used for adhesion. There is no sense in buying smoother copper on the resist side if it will be treated with black oxide. Figure 2 shows examples of this. Technology Drivers Cost effectiveness Use the CCL and PP that is the most com- monly produced as these are always avail- able and have the best cost relations. Be cost- aware of how the material you use ranks it- self as a cost index given by your PCB suppli- ers. Table 1 shows cost indexes for common pre-pregs. The cost of material in a PCB to- day averages 30% of the total cost, regardless of how cost-effective your PCB supplier's pro- cesses are. If they don't have good relations upstream with the material suppliers, you are not controlling the cost. Table 2 shows cost in- dexes for laminates. Table 2: Laminate average cost indexes from six PCB suppliers. Figure 2: The copper roughness on a PCB can vary considerably, which is very important to electrical performance. Thickness (mm) Cost index %HFFR 0,050 1,31 0,063 1,23 0,076 1,07 0,100 1,00 0,127 1,03 0,150 1,10 0,200 1,11 0,250 1,34 0,300 1,41 Table 1: Prepreg cost index averages from six PCB suppliers.