News
Outsourcing RoHS-Compliant Production at a Distance
Published: 27 January 2006
by Eric Liew, Fadzol Zaman and Sivakumar Thanupillai
An Asian EMS provider's perspective on challenges and potential solutions.
Outsourcing electronics production offshore has always been a more complex process than localized manufacturing strategies. RoHS compliance adds product redesign, supply base requalification, process qualification and the learning curve issues associated with a standard that is still in development to the prior complexity of communicating at a distance across multiple time zones.
This article discusses one Asia-headquartered EMS provider's Pb-free process implementation strategy and some typical challenges associated with managing RoHS-compliant process transition at a distance. It also discusses the issues that arise as the result of cultural differences in customer business models across multiple regions.
 FIGURE 1: A Pb-Free SMT line in Beyonics Technology's Kulai, Malaysia campus. |
In migrating to Pb-free processes, Beyonics Technology Ltd. (beyonics.com) encountered a number of issues. These included:
- Upgrading reflow and solder wave equipment to meet higher melting temperature process specifications.
- Formulating suitable operating procedures to identify and segregate Pb-free materials to prevent contamination.
- Changing incoming part inspection practices to identify part integrity for consigned and direct purchase material.
- Re-optimizing process parameters and process design standards to meet different alloy behavior characteristics.
- Evaluating issues related to components' heat sensitivity, terminal finishes and molding compounds.
- Higher indirect material costs.
In addressing these challenges, Beyonics focused on five areas:
- Collaboration with customers to ensure compliance with their internal Pb-free initiatives.
- Employee training on Pb-free processes and control.
- Development of internal processes through use of a pilot line.
- Collaboration with customers and suppliers to ensure access to RoHS-compliant material in line with process parameters.
- Implementation of new process monitoring equipment to manage tighter process windows and monitor contamination.
In the transition to Pb-free and RoHS compliance, the company did not embark on process alone. Materials suppliers, equipment suppliers and technical organizations were all great resources in developing and validating acceptable processes.
Two Business Models
Beyonics began implementing its Pb-free process in 2003 to support a Japanese customer. Japanese manufacturers were strongly advocating elimination of hazardous materials in their processes while the RoHS directive was still in development. The Japanese standards closely followed RoHS compliance. In April 2005, Beyonics' processes were enhanced to comply with the RoHS directive. Currently, the company supports volume RoHS-compliant production for a range of customers from multiple regions in the disk drive, wireless applications and consumer electronics industries in Singapore, Indonesia and Malaysia. In addition, the company has two business models to support the preferred business framework of its Japanese customers and U.S./European customers.
The key difference in the two models is degree of control. In the Japanese model, the supply base, inventory management and process choices are controlled by the OEM. In the U.S./European model, the EMS provider is responsible for material procurement, inventory management, DfM recommendations and process control. In both cases, the EMS provider is expected to use its manufacturing expertise to improve efficiency where possible and the OEM and EMS provider team in continuous improvement efforts. The differences in business models drive differences in EMS provider responsibility for RoHS transition issues.
Beyonics uses a SAC 305 alloy in its manufacturing process. It was chosen through internal process studies, though it is consistent with the recommendation of IPC Solder Products Value Council. This alloy melts at 217°C. As tin is the major element, reflow temperature is high. The higher temperature increases the oxidation rate and tin has a higher oxygen affinity. Since the oxidation rate is enhanced even further, an inert nitrogen atmosphere is used in the reflow process for most products.
Also, the effective process window is narrower because these solders have a higher liquidus temperature, and materials present in the PCB limit the maximum temperature they can sustain for a given amount of time. Nitrogen reflow supports these narrower process windows because it contributes to improved wetting, shinier appearance, fewer voids in BGA and QFP joints, and more consistency in BGA balls. As there is less flux residue in a nitrogen atmosphere, in-circuit test yield is enhanced, because test probes easily penetrate the flux to the test point.
Typical Project Transition Issues
Product Redesign. While each project may have unique redesign needs, Beyonics' basic DfM guidelines identify the following as areas of focus:
- Stencil design. In stencil printing some factors will change, others will not. Solder paste printability depends heavily on flux formulation but not on alloy type. Because Pb-free alloys do not spread or wet as well as lead alloys, any solder paste printed on the PCB will remain close to where it was printed. This may affect the accuracy of the printing equipment to align stencil apertures to PCB pads. Concerns include variation of positional accuracy of PCB, variation of alignment capability of printer and variation in the stencil itself.
- Design of experiments conducted to study stencil aperture, paste volume, PCB pad size, printer parameters are important in developing a manufacturable product.
- PCB layout design. PCB pad size and shape may change; however, design guidelines in this area can vary based on product complexity.
- Component selection. The component's temperature tolerances or maximum ramp rate (degrees/sec.) have always been important for Pb-free processing. Evaluate each component's ability to withstand heat, and understand the compatibility of its lead finish and moisture sensitivity level (MSL) with the Pb-free process parameters.
Supply Base Management and Inventory Control. Material integrity is as much of a challenge within the Asian supply base as it is in the U.S. Within the Japanese OEM model, customers test all material prior to consigning it. Within the U.S./European model, the standard practice of combining incoming inspection and preferred suppliers willing to certify material as RoHS compliant is used.
Incoming quality assurance practices include a verification process which checks the RoHS identification list from each supplier and the latest threshold value information of the RoHS-relevant substances. Invoices and analysis/inspection data is also checked for each delivery batch. Finally, the inspection report must contain a visible RoHS stamp, shipment date and lot/batch number information to support traceability should contamination issues subsequently be detected.
RoHS-compliant material is physically segregated from material used in SnPb product. Employee training includes material on RoHS-compliant packaging markings and appropriate storage procedures.
Process Control and Product Compliance. Strict internal procedures regulate storage of material on the production floor; operators follow a material integrity verification procedure. Solder purity in production areas is monitored daily using a Malcom STA-2 impurity checker. Solder joint quality testing includes cross-sectional and structural inspection.
 FIGURE 2: An operator verifies machine programming prior to production start in a Pb-free line in Beyonics' Kota Tinggi, Malaysia facility. |
Some projects include third-party audits of sample lots of finished boards by the solder supplier to verify RoHS compliance of materials. In addition, customers may also have incoming inspection procedures.
When unacceptable levels of defects are detected, joint process studies are initiated.
Pb-free compliance is implemented in stages. On one cordless phone product, allowable Pb contamination (impurity) level in wave solder was reduced from an initial control limit of below 3000 ppm at process initiation in 2002 to a level below 800 ppm in 2005 to comply with RoHS.
Areas to Audit
Areas to be audited prior to transitioning Pb-free projects to an offshore contract include:
- Compatibility of contractor support infrastructure with services needed.
- Ability of contractor to support redesign efforts and component sourcing changes.
- Internal supplier processes for material integrity and traceability.
- Internal and third-party audit procedures to monitor contamination.
- Internal procedures related to monitoring changes in the RoHS directive requirements and ensuring smooth implementation and appropriate customer notification/approvals for any resultant process or materials changes.
- Track record of supporting customer quality and process improvement initiatives.
- Communication processes between customer, contractor program and engineering teams.
- Ability to support evolving process requirements.
Implementing RoHS-compliant projects is complex because there are many variables to consider. Distance increases that complexity. Understand both a contractor's internal processes and the business models it uses for customer interface. While offshore sourcing does complicate communication, in some cases it also provides access to a greater base of knowledge. For instance, contractors with Japanese customers may have several years of volume Pb-free production experience.
Initial screening of offshore sourcing options should include onsite evaluation of each contractor's internal systems. Audits should also focus on analyzing the contractor's preferred business model, range of internal RoHS transition expertise/support capabilities, past track record with projects of similar size and scope, and team communication methodology.
Eric Liew, Fadzol Zaman and Sivakumar Thanupillai are in technical management positions at Beyonics (beyonics.com) in Indonesia and Malaysia. For questions related to this article contact Raymond Yee; raymondyee@sg.beyonics.com.
