The roles of IC packaging substrate are mainly to provide signal transmission, power distribution and heat dissipation between the IC and PWB board (or Component of system) and to act as a space transformer between the fine line dimensions of the IC and the coarse line dimensions of the PWB board.
Current key semiconductor packaging requirements are cost competitiveness, miniaturization, better warpage performance, better form factor and higher electrical & thermal performance. Amkor is underway to continue the substrate-related research and development in order to respond to above market trends and semiconductor packaging requirements. Fig-2 is a chart showing Amkor key substrate technology development directions.
In general, substrate cost occupies a large percentage of total package price. Therefore, cost effective substrate development will be a key enabler to develop cost effective packages. Recent key development directions for cost effective substrate are to replace SOP(solder on pad) substrate with BOL(bond on lead) substrate, to reduce substrate layer count (ex. 4 layer to 3 layer conversion), and to develop lower cost fine line/space patterning methodology like ETS (embedded trace substrate).
For better electrical performance, low loss substrate solutions like low Df dielectric material and lower Ra trace surface technology have been developed and used. Recently, core material having 0.004 Df@60GHz was developed and started to be used for some customer high frequency devices requiring higher electrical performance. And, lower Ra trace surface substrate has also been developed and used recently for network communication FCBGA packages as a low loss solution (Fig-7.). And, for mobile application processor, EPS (embedded passive in substrate, Fig-6.) which has shorter electrical paths between application processor IC chip and capacitor than normal non-EPS substrate has been used for several years for better clock speed of flagship smart phones in the market. And, recently thermally enhanced core and prepreg materials featuring around 3 W/mk thermal conductivity are being developed to meet future potential substrate thermal conductivity requirements.