May, 2019


www.us- tech.com


Reducing CTE Mismatch Defects in Flip Chip Reflow


Continued from page 65


ence the spread size of the solder joint. This determines the area of interface between the substrate and bump and will be more prone to cracks if the timing is too long. Typical TAL values are between 50 and 60 seconds. It can be seen in Figure 3 that


³120 micron copper pillars or simply by using soft solder bumps, the effect of these spikes may be less detri- mental. With further miniaturiza- tion, brittle ELK dielectric with cop- per pillars and much finer pitch means less flexibility and more sen- sitivity to CTE-related cracks. Such products will require tighter control of the cooling rate. TrueFlat negative pressure


Improving Automobiles


Continued from page 63


prior to starting the vehicle, thereby avoiding damage. These technologies are currently being evaluated by leading automotive electronics man- ufacturers, with promising results. Beyond the battery pack is the


power inverter, which draws stored power from the battery to drive the electric motor. Like the battery com- ponents, effective heat dissipation through the use of TIMs is critical to DC-DC inverter performance. In addition, because the inverters are conducting such high switching fre- quencies, highly-reliable intercon- nect materials that offer an alterna- tive to tin-lead solders (which could be phased out as early as 2023) are required. Henkel silver sintering pastes


are already being integrated for this purpose. Elsewhere, in the battery management engine control units (ECUs), other advanced materials, such as solder, conformal coating chemistries, potting compounds, sealants, and inks, combine to maxi- mize the operation of NEVs. Throughout the entire automo-


tive system, advanced electronic materials are present, providing reli- able performance of ADAS technolo- gies. These include long-lasting interconnects for electrical function- ality, temperature management of critical battery components, and pro- tection and sealant materials to keep harmful environmental influences from diminishing functionality. Together with today’s leading auto- motive electronics manufacturers, materials innovators are driving toward a world with improved road safety, better vehicle control and comfort, and reduced emissions. Contact: Henkel Electronic


Materials LLC, 14000 Jamboree Road, Irvine, CA 92606 % 714-368- 8000 E-mail: eva.laus@henkel.com Web: www.henkel-adhesives.com r


the cooling rates achieved with the controlled cooling from ATC are more consistent, even as those compared to the standard PYRAMAX TrueFlat oven. These spikes over short dura- tions of five seconds are called micro spikes. How critical are these micro spikes to the reflow process? If the pitch is wide, such as


reflow technology ensures that thin substrates on carriers are kept flat to reduce die tilt and in direct contact for effective heat spreading during the reflow process. ATC comple- ments TrueFlat technology in reduc- ing micro spikes for optimal control of CTE mismatch-related defects. Contact: BTU International,


Inc., 23 Esquire Road, North Billerica, MA 01862 % 978-667-4111 Web: www.btu.com r


See at NEPCON China, Booth 1E50, and at SMTconnect,


Hall 4 Booth 551 Figure 3: Profile comparison — standard vs. ATC.


Page 67


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