SMTA International Conference Proceedings


SOLDERBALL(TM) INTERCONNECTS FACILITATE SMT REFLOW & ELIMINATE CO-PLANARITY ISSUES FOR SUB-ASSEMBLIES AND POWER MODULES

Author: Carlos Juvera et al.
Company: Autosplice Inc.
Date Published: 9/25/2005   Conference: SMTA International


Abstract: The formation of robust Surface Mount Technology (SMT) interconnects between a modular PCB sub-assembly (PCBSA) and host/motherboard PCBs is a key issue for manufacturers of power converters and other subassembly modules. Power modules, manufactured as a PCBSA, are often parallel stacked to a customer’s host PCB. Such modules are representative of many subassemblies that require interconnections with a high degree of mechanical and electrical integrity when migrating to an SMT compatible package.

Traditional power converter modules have been manufactured as through-hole technology (THT) packages. This paper introduces termination designs, applicable in converting axial leaded THT devices to an SMT compatible package, that can meet the requirements for high current and power applications. The conversion to SMT packages requires managing coplanarity variances between the PCBSA and motherboard during the final assembly to ensure that robust solder joint connections are formed.

SMT packages offer substantial reduction in size, weight and cost, while displaying enhanced reliability, thermal, and electrical performance. The transition from THT to SMT is logically facilitated by maintaining design and layout consistency between the new SMT and old THT package styles. Assembly reliability issues, with regards to hole fill in THT designs, are effectively addressed.

The use of new Solderball Pin1 technology addresses the above issues by providing an efficient method for automated placement of interconnects onto the module PCB, with an integrated SMT-ready solder-ball interface on each pin for soldering to the motherboard. During reflow, the weight of the module enables the Solderball pins to settle into the host board. The Solderball pins automatically compensate for coplanarity variances as high as 0.020 in., while promoting optimal solder wicking as each solderjoint is formed.

This paper provides an overview of the solderball-pin technology and presents a practical example of its application in double-sided surface mount technology (DSSMT) power modules, that are compatible with endcustomer SMT production methods.

Key words: Solderball pin, parallel stacked PCBs, power converter modules, SMT, coplanarity.



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