PTFE / RFMW PCB Issues
Voids: Desmear and Ash
To insure that vias are properly desmeared and material hole walls activated, we utilize a two-step desmear process. This process first requires that the panels be processed through a chemical desmear that has been optimized for micro- and blind vias. This line has been outfitted with long-stroke agitation and flight bar vibration to enhance fluid movement and prevent air bubble entrapment. The panels are then submitted to a plasma conditioning process in our March Plasma System. PTFE materials contain Teflon, which has the primary property of not allowing other materials to adhere to it. As such, copper plating is not possible without Plasma Activating the surfaces of the hole wall.
PTFE materials have the property of elongating during processing. This often makes primary and soldermask imaging very difficult. We attack this issue in the following ways:
Our operators are trained in specific methods of handling these materials throughout each process. This minimizes elongation due to handling and processing.
We have studied a large extent of various PTFE systems and core thicknesses from Rogers, Taconic, and Arlon to determine scale factors in standard processing in combination with copper retention percentages. A key instrument in these studies is the use of the PerfecTest system and resulting knowledge database. We consult this database each time a new part number is produced.
Automatic Alignment Imaging Systems
We have installed 4-camera automatic alignment imaging systems (4 units between 2007-2008). These units utilize a 4-camera system to align the top and bottom artwork to within 0,5 mils. They then make micro adjustments to the panel position for best-fit panel-to-artwork alignment.