Flexible circuit materials Adhesiveless

Each has different manufacturing processes and advantages as the major materials of HDI flexible circuits. Table 61.13 shows basic performances of typical adhesiveless laminate materials. 

Currently, there is no perfect solution that satisfies all requirements including cost. Suitable adhesiveless laminate materials should be chosen according to the specifications of the final flexible circuits and the convenience of manufacturing processes. 

If adhesiveless laminates are used as the major materials, high temperatures can be used with lead-free soldering. In the case of SMT assembling, the flexible circuit should be fixed on a carrier frame. This allows it to be processed by the same mounting and soldering equipment as used for rigid boards. 

A wirebonding process similar to COB has been applied for high-density flexible circuits without serious changes. Due to the high heat resistance of new adhesiveless laminates, standard bonding materials and equipment for flexible circuits can be used (see Fig. 64.6). 

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