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52 SMT Magazine • August 2015 Proposed Warpage Acceptance Criteria and Differences with Existing Industry Specifications It is the view of the collaborating companies that the current JEDEC Publication 95, SPP-024 Issue A and JEITA ED-7306 warpage specifica- tions are too generous to prevent the occurrence of HoP defects in SMT assembly. Consequently, the authors are proposing the following revi- sions to existing specifications: 1. An absolute maximum warpage of 0.09 mm (3.5 mil) during the reflow stage of sol- dering independent of BGA body size and I/O count. The reflow stage is defined as the entire period where the BGA component tempera- ture exceeds 150°C. For example, this could be 150°C to 245°C back to 150°C for larger BGAs and 150°C to 260°C and back to 150°C for smaller BGAs. 2. The revised acceptance criteria would only apply to BGAs with a 0.8 mm pitch or greater. 3. The proposed acceptance criteria apply only to applications that use 0.125 mm (5 mil) or 0.150 mm (6 mil) stencil thickness. 4. Fine pitch BGAs (equal to or less than 0.65 mm pitch) with smaller solder spheres are likely to require a lower value of maximum warpage. As a future consideration, the finer pitch com- ponents must be addressed as more data warp- age emerges. Discussion and Suggestions for Follow-on Work This collaboration between OEMs and EMSs has confirmed that a large number of users in the industry are confronted with the HoP de- fects in product manufacturing. It is the view of the authors that component warpage plays a significant role in the formation of the HoP defect. An acceptance criteria for BGAs with 0.8 mm pitch and above is proposed that is more rigorous with lower warpage limits than the current JEDEC and JEITA industry specifications addressing component warpage. The proposed acceptance criteria were based primarily on end user application data and experience rather than extensive DOE-like studies. Although it is the view of the authors that the proposed acceptance criteria are sound and will further minimize HoP defects, a lot of work is need- ed within the industry to reach an agreement between component suppliers and the users (OEM/EMS). The following is a list of suggested follow-on work: 1. Standardized test methods are needed for measuring warpage and correlating the warp- age measurements to manufacturing process yields. 2. Warpage characterization should be per- formed on a variety of components having dif- ferent levels of warpage in order to better un- derstand the onset of HoP as it relates to com- ponent warpage. This will require a significant, coordinated effort between industry standards bodies, packaging houses, device suppliers, end users, and consortia A wide range of compo- nent sizes, pitches and degree of warpage are needed for further testing in order to better un- derstand how the revised specification works as a function of the these parameters. 3. This paper presents case studies using 0.125–0.150 mm (5–6 mil) stencil on BGAs of 0.8 mm pitch and above. A better understand- ing is required for the same component type Table 5: Comparison of the oEM/EMS proposed specification for 0.8 and 1.0 mm pitch BgA to the JEiTA and JEDEC specification. WARPAGE ACCEPTANCE PROPOSAL continues FeAture