Original Date: 06/05/2006
Revision Date: / /
Information : Low-Residue Flux and Solder Material Sets for Soldering Processes
Rockwell Collins has shifted from the use of high-solid content, rosin-based flux materials within its soldering processes to the use of low-residue, moderate-activity fluxes. Driven by a corporate dedication to sound environmental practices and the negative reliability impact of flux residue-induced corrosion, the company uses a multiobjective approach to material and process selection. This approach ensures that production quality and end- item reliability are maintained while sustaining environmentally friendly materials within the manufacturing process. Rockwell Collins has experienced improvements in processing characteristics and improved cycle times, with no negative impact to quality and joint integrity.
Rockwell Collins’ manufacturing processes formerly used traditional electronic assembly flux materials with high- solids contents (i.e, rosin-based materials with limited activity level). These materials were disadvantageous in that they were difficult to remove from completed electronic assemblies and were susceptible to corrosion and associated failure mechanisms.
Beginning with the 1988 Montreal Protocol, legislation and Presidential policy pushed to eliminate the use of chlorofluorocarbons (CFCs) from manufacturing processes. CFCs were used extensively in cleaning chemistry within the electronics industry. In response to the need to eliminate banned CFC-based chemicals, the electronics industry experienced a revolution of flux materials used in common soldering processes. New low-residue, moderate-activity flux materials are currently qualified for Rockwell Collins’ soldering processes. These materials offer a high level of corrosion resistance in a fully reacted condition. New flux materials are designed to aggressively promote solderable surfaces while sustaining the corrosion resistance in post-assembly field environments.
The selection of the appropriate flux and solder material results from an integrated soldering process strategy that considers the soldering, fluxing, and cleaning processes simultaneously (Figure 3-2). Rockwell Collins established this complete approach after failed attempts at optimizing each process independently. Only through the concurrent consideration of flux materials, cleaning process chemistry, and inert atmosphere reflow soldering methodologies has Rockwell Collins been successful in proposing identification and specification of low solids, low-residue flux and solder paste materials.
The benefits of this process improvement include: Extended process windows with respect to cleaning time duration, cleaning effectiveness, and a reduction in cleaning cycles required
No detrimental impact on solder joint quality/integrity for most applications
Improved process cycle times resulting in delivery schedule benefits
Figure 3-2. Common Low Solids, Low-Residue Flux and Solder Paste Materials
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