Flexible circuit manufacturing Process, basic

The majority of flexible circuit manufacturers start the process with copper-clad materials. The properties of these materials depend on the capabilities of laminate manufacturers, even though the same base films and copper foils are used. To choose the right materials, manufacturers must carefully consider the basic properties of each laminate material. 

Tape-automated bonding (TAB) has not been considered as a type of flexible circuit because of the slightly different manufacturing processes. However, the basic construction and materials of the final products are the same therefore, TAB is categorized as a type of flexible circuit in this book (see Fig. 61.2). 

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. 

The process of manufacturing with film coverlay is very complicated, which makes process automation difficult and increases the cost. The manual registration process and the use of unstable film material are major issues when considering film coverlay for HDI flexible circuits due to small hole capability and lower dimensional accuracy. Basic properties of the typical materials are shown in Table 61.14. 

The generation of fine lines is the most basic process in building high-density flexible circuits. Three basic manufacturing concepts have been developed ... 

On the other hand, it is a basic concept that failures should be eliminated as early as possible to ensure a high process yield, from a quahty control standpoint, especially for long manufacturing processes. Figure 67.2 shows the general manufacturing flow of high-density flexible circuits, and a recommended inspection procedure. 

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