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Mention copper to almost anyone in the PCB industry these days and the first thing that springs to mind is the ongoing price increase. Although copper pricing is not directly monitored by BPA, the impact on the price of laminate and PCBs is monitored through BPA's quarterly survey for its PCB Information Service. In the short term, forecasted increases on the demand side for copper prices are likely to remain at least at the current level. The trend in copper usage has diverged in the fact that a number of different applications now exist.
At one time, 1 ounce (35um) copper was standard, but the average is now 0.5 ounces. Using thinner copper, if the design will allow, can, to some extent, offset a price increase. However, one segment of the PCB industry which is particularly vulnerable to copper prices is the automotive sector, where recent developments have seen the introduction of thick copper PCBs for smart fuse boxes and power electronics. These boards use 4 ounce, 6 ounce and 10 ounce copper--up to 20 times the standard thickness.
For Microvia (HDI) and particularly IC package substrates, the trend is toward a foil thickness of 9um or less. As line/space reduces below 30um, for semi-additive processing, the preference is for a copper start thickness of 5um or less. Theoretically the thinner copper should be less costly, but ease of handling is provided by a support carrier which is either peelable or for sacrificial etch and both add to the cost. An option used by many fabricators is to start with a thicker copper (12/18um foil thickness) and etch down to the desired starting thickness. However, at some point, the surface roughness and yields become unacceptable and the cost-yield-performance equation forces the fabricator over to the ultra-thin copper.