Why do you start with 9µm copper foil on the outer layers for HDI boards? I thought you start with a 18µm copper foil to reach a finished copper thickness of 35µm?

The answer to why we start with a 9µm copper foil when we produce an HDI microvia board is that by doing so we can use less energy during the laser process, which means that the laser can be controlled more accurately and a clean hole can be achieved.

The finished copper thickness of 35µm according to IPC will nevertheless be reached in the subsequent processes.

Why you can’t offer HAL leadfree for a material thickness of 0.80mm?

The answer to this question relates to our production process. After the hot dip in the HAL leadfree process, the surplus tin is blown off by air pressure. During this process the material is cooled down and may start to oscillate.

If this happens it’s possible that we get a wave-like tin surface. And this would be a quality problem, so we don’t offer this combination.