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56 DESIGN007 MAGAZINE I AUGUST 2024 rial combinations, and (2) various asymmet- ric hybrid stackup constructions on mechan- ical reliability performance using a qualita- tive approach. Unlike most other research that uses test coupons as the subject, a pro- duction-level data center mainboard design was used in this study, which provides more reliable test results and more accurate assess- ments. Reliability test methods and results con- cerning warpage, delamination, via reliability, and brief signal Integrity comparison will be discussed in this paper. Recommendations on PCB manufacturing and design guide- lines to mitigate the reliability risks associated with asymmetric hybrid PCB will also be pro- vided. Introduction Reliability risks (warpage, delamination, conductive anodic filament, and via reliabil- ity) remain the major concerns in the usage of asymmetric hybrid PCB stackups. Conven- tional wisdom suggests that the manufactur- ing challenges and reliability risks of asymmet- ric hybrid PCB stackups are even higher than with symmetric hybrid PCB stackups. is research aimed to (1) understand the effects of different copper-clad laminate (CCL) material combinations and various constructions on the reliability performance of the asymmetric hybrid stackup, and (2) establish design and manufacturing guidelines to mitigate the reli- ability risks of the PCB, using a qualitative approach. e assessment of reliability risks in the PCBA process, such as solder joint integrity, shock and vibration performance, as well as effects on components, falls beyond the scope of this research. Stackup Designs A 110-mil thick stackup (a thickness cov- ers the majority of the data center mainboard design) containing 2 ounces of inner copper has been designed. Various asymmetric hybrid constructions for the stackup are considered in Table 1. Table 1: Stackup design strategy