The Challenges of Higher Temperature Lead Free Process --An Introduction to Laminates with Higher Heat Resistance and Reliability
Introduction As the environmental consciousness in the world runs high, Directive of the European Parliament and of the Council on the Restriction of the Use of Certain Hazardous Substasnces (RoHS) of European Union has required to restrict the use of lead (Pb), cadmium (Cd), mercury (Hg), hexavalent-chromium (Cr+6)compounds, polybrominated biphenyl (PBB), and polybrominated diphenyl ether (PBDE) from July 1st, 2006. Therefore the tin-lead (SnPb) in solders for assembly used in the past must be migrated to the lead-free alloy solders. The melting point, lead free solder temperature, and wave soldering temperature of lead-free solder are more than 20-30℃ higher than those of traditional tin-lead solder.In addition,the lead free solder is less adhesive to tin, most assembly houses may consider to raise the temperature in solder to improve manufacturability and improve the throughput. Higher operating temperature and longer cycle are serious impacts to the heat-resistance for traditional FR4 material. Hence, the back-end assemblers reported abnormal deleamination sporadically, undoubtedly, it claimed a new era of technology of high heat-resistance laminates. The old idea that high-Tg means high heat-resistance is no longer true in a lead free era. Instead, characteristics such as the temperature of decomposition (Td), time to deleamination by TMA (T-260/T-288), coefficient of thermal expansion (CTE), etc., are major referenced indices by the PCB industry in choosing the high heat-resistance laminate materials. Among them PN-cured laminate materials is the most favorable, mainly because the property of resin of PN-cured laminate materials is with more aromatic structure, which has relatively lower water absorption and better heat resistance: Td > 350℃ 、T-288 > 15min、and CTE value on total expansion <4％. In addition, consider from the cost, it can also be improved based on dicy-cured FR4 to make its price and manufacturability close to those of currently used ordinary FR4, and its reliability can meet high temperature lead free process.
Peter Liang
Nan Ya Plastics Electronic Materials-CCL
国际会议
上海
英文
2008-03-17（万方平台首次上网日期，不代表论文的发表时间）