SMTA International Conference Proceedings


LEAD-FREE HAND SOLDERING: NEW TECHNOLOGIES FOR ENHANCING THE WEAKEST LINK IN THE LEAD-FREE REWORK AND REPAIR PROCESS CONTROL CHAIN

Authors: Mark Cannon, Bob Klenke, and Phil Zarrow
Company: ERSA GmbH and ITM Consulting
Date Published: 9/24/2006   Conference: SMTA International


Abstract: With lead-free mass soldering processes approved and implemented, increased demand is placed on rework and repair as a significant challenge that needs to be addressed by board level assemblers. Long considered as the weakest link in the lead-free process control chain, lead-free hand soldering requires rigorous control of the thermal process given the higher processing temperatures and reduced process window. The paradox between higher process temperatures of lead-free alloys and the thermal threshold of electronic components during the rework and repair process forms the basis of the lead-free challenge.

By examining lead-free hand soldering more closely, it is known that a repeatable and stable process is dependent solely on three factors: time, temperature and operator technique. Time, or the dwell time of the solder iron tip on the solder joint, and technique are dependent on operator skill and training. Temperature however, is governed by the actual temperature of the solder iron tip during the soldering process and is dependent 100% on the technology of the soldering iron. Implementing a greater degree of repeatability and stability of the hand soldering process are critical ingredients to implementing a successful rework and repair process and reducing thermally induced component or board defects.

Implementing a successful lead-free rework and repair operation, the manual soldering process must be evaluated on three levels with respect both to operator and solder iron related issues; a process control and quality aspect, a stability and repeatability standpoint, as well as from an operational cost perspective. Given the fact that many companies already running lead-free in production volume are consuming up to one solder tip per day, per operating station, at significantly high replacement cost, the operational cost factor has a significant impact in a competitive manufacturing environment.

This paper describes a true breakthrough technology in leadfree manual soldering that greatly enhances solder joint quality, guarantees process stability and significantly lowers operational cost. A case study will be presented that illustrates a design-for-experiment to quantify and insure lead-free solder joint reliability. The proper selection of tools and procedures to conduct a hand soldering skills audit and training methodology assessment to quantify the consistency of rework and repair operator proficiency will be defined.



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