EXECUTIVE SUMMARY

PROGRAM DESCRIPTION

OBJECTIVES

• Phase 1 - Solderability of Pb Free Components
  
  
  • Evaluate the solderability performance of component Pb-free lead finish types versus a baseline of Sn/Pb component finishes.
  • Evaluate the solderability performance of component Pb-free lead finish types with respect to different board surface finishes.
  • Evaluate the solderability performance of component Pb-free lead finish types with respect to solder paste flux type. A water-soluble and a no clean solder paste will be selected.
  • Evaluate the solderability performance of component Pb-free lead finish types for QFP, BGA, SOIC, chip resistor, chip capacitor, and chip inductor component forms. In addition some simple through hole jumpers/connectors will be tested.
  • Evaluate the solderability performance of component Pb-free lead finish types with respect to profile extremes for reflow and wave solder.
  • Characterize the effects of reflow profile parameters (ramp rate, pre-heat time, soak time, soak temperature, time above liquidous, peak temperature, and cooling rate) on solderability of components with select Pb-free lead finish types. This will be conducted for only those components and lead finishes exhibiting the largest number of defects and smallest process window. Wave solder profile extremes such as contact time will also be studied to a lesser degree.
  
  
• Phase 2 - Lead Free Solder Process Technology Transfer
  
  
  • Qualify lead free assembly processes.
  • Technology Transfer documentation for the lead free process based on previously proven techniques for transferring the process technology to participating customers technical staff.
  • Substrate design guidelines to enable participating customers to incorporate robust lead free solutions into current and next generation products.
  • Complete process documentation of the lead free process solution.
  • Interconnect reliability qualification of lead free component assemblies.
  • Process installation guidelines for lead free processes to be installed on a qualified production line at participating customers facilities.
  • Hands-on lead free assembly process training materials to be used for on-site, hands-on training

SCOPE OF WORK

1. Procure QFP, BGA, SOIC, and chip components with a wide range of Pb-free lead surface finishes. Lead finish types very significantly from component type to component type and manufacturer to manufacturer. Hence the available lead finish types will vary for each component. The lead finish types that might be explored based on the availability from manufactures may include:
   
   BGAs: Sn/Ag, Sn/Cu, Sn/Ag/Cu, Sn/Bi, Sn/Ag/Bi, Pb/Sn
   QFPs: Ni/Au, Ni/Pd/Au, Ni/Pd, Ag, Sn, Pb/Sn.
   SOIC: Ni/Au, Ni/Pd/Au, Ni/Pd, Ag, Sn, Pb/Sn.
   Chip: Sn, Ni, Pd/Ag, Pb/Sn
   
   In order to ensure repeatability of plating finished, components will be obtained directly from suppliers as opposed to distributors. Components in each package type will be obtained from two or three different component vendors. Six component types will be studied. Specific components will be based on availability of testable (daisy chain preferred) packages from commercial manufactures. Two vendors from each component category below will be selected to insure consistent metallization finishes. These include:
   
   QFPs (64 IO, 128 IO, or 256 IO)
   BGAs (1.27 to 1.00 pitch; 256, 564, or 1156 IO)
   SOIC: (1.27 pitch, 20, 24 or 28 IO)
   Chip resistors (0603 or 0402 - 1.6 x 0.8 mm chip or 1.0 x 0.5 mm chip)
   Chip capacitors (0603 or 0402 - 1.6 x 0.8 mm chip or 1.0 x 0.5 mm chip)
   Chip inductors (0603 or 0402 - 1.6 x 0.8 mm chip or 1.0 x 0.5 mm chip)
   
   
2. Design a new test vehicle assembly that is electrically testable using daisy chained devices including QFP, BGA, SOIC and chip components with participating customers input on requirements. In addition, simple through hole components such as small jumpers or connectors will be included to allow mixed technology testing.
   
   
3. Procure test vehicle boards with surface finishes. Two different board finishes will be tested. Copper/HASL and an Immersion Tin (Sn) surface finish will be evaluated. HASL is a commonly used surface finish, and Sn finishes have been receiving attention as an environmentally friendly alternative to Hot Air Solder Leveling (HASL). A screening test will be performed to determine the affect of board aging on solderability. Test boards will be subject to 85OC/85%RH for 48 hours and then assembled.
   
   
4. Initiate the Component Solderability Screening study.
   
   
5. Perform screening experiments based on solderability measurement techniques consisting of a dynamic solder wetting test providing quantifiable measurements and visual records. Components will be tested as received, as well as subjected to process/storage conditions such as a glue cure step or a component bake-out step. The solderability tests will be a dynamic wetting measurement used to rank order the solderability of Pb-free lead finishes relative to Sn/Pb lead finishes. Component lead finishes performing equivalently to Sn/Pb lead finishes will be identified. Flux systems to study will be selected with participating customers.
   
   
6. Screening experiments will be performed on components with lead finishes performing equivalently to Sn/Pb in the solderability tests in item 5. The purpose of these screening experiments will be to confirm that these select Pb-free surface finishes perform equivalently to Sn/Pb surface finishes over the target process window of substrate surface finish, solder paste material, and reflow profile.
7. Initiate the Solderability Process Window Characterization study
   
   
8. Perform a design of experiments varying the Pb-free lead finishes, board surface finish, paste material type, and solder profile. The second phase will be based on design experiments characterizing the complete process window of the most challenging Pb-free lead finish.
   
   
9. Assemble test boards using different solder pastes, board finishes, reflow or wave solder profile, and component lead metallizations based on a design of experiments. Solder paste materials will be selected jointly with participating customers. Ramp rate, preheat time, soak time, time above liquidus, peak temperature, and ramp down rate are the factors to be studied in the reflow profile. Three different ramp rates will be studied, as well as high and low values for time above liquidus and peak temperature. Factors such as contact time and solder pot temperature will be studied for wave soldering.
   
   
10. Determine affect of process, board and component variables on solderability of components. Characterization of the solderability will be based on X-ray inspection, electrical continuity testing, and Automated Optical Inspection (AOI) of the solder joints, solder fillets, and solder surface finish. Optical inspection will be based on IPC 610C standard. Additional factors to be considered will be solder joint voiding, electrical resistance/impedance, and solder joint defect generation (solder balling, solder beading, tombstones, bridges, insufficient fillet, and component skew).
    
    
11. Analyze the reliability of the various Pb-free lead finishes based on the process exhibiting the best solderability for each finish. A sampling of measurements will be made in-situ for all components and the remainder will be tested at set intervals. The Mean Time to Failure data will also be compared to shear and pull test data. Shear tests will be performed on chip components and pull tests will be performed on individual IC leads.
    
    
    • Air to air thermal cycle testing
      
      
      • -40 to 125 C
      • Based on joint industry standard JESD22-A104-A
      
      
    • Temperature Humidity Bias of the Components and Board Surface Finishes
      
      
      • 85C, 85% RH
      • Bias voltage to be determined
    
    
12. Perform the technology transfer of process, materials, and design knowledge to participating customers engineers.

1. Installation, process qualification and transfer of a qualified lead free assembly process compatible with a range of SMT components demonstrating printing process capability, placement process capability and first pass yield DPMO.
   
   
   1. Print and Reflow Equipment Process Capability Requirements and Procedures
   2. Qualified Materials Specifications
   3. Design guidelines for PWBs and high density microvia substrates.
   4. Design for Manufacturablity Guidelines.
   5. Component Termination Specifications
   6. Qualified Process Recipe and Parameters
      
      
      • Rework-Repair
      • Stencil Printing
      • Reflow
      • Inspection
      
      
   7. Process Installation Guidelines
   8. Basic Process Window Specifications
   9. Process Requirements
   
   
2. Hands-on technology transfer workshop and associated documentation for the lead free process based on previously proven techniques for transferring the process technology to participating customers staff. This is performed at Engent's Advanced Assembly Technology Center.
   
   
3. Process documentation.
   
   
   1. Print and Reflow Equipment Process Capability Requirements and Procedures
   2. Qualified Materials Specifications
   3. Design guidelines for PWBs and high density microvia substrates.
   4. Design for Manufacturablity Guidelines.
   5. Component Termination Specifications
   6. Qualified Process Recipe and Parameters
      
      
      • Rework-Repair
      • Stencil Printing
      • Reflow
      • Inspection
      
      
   7. Process Installation Guidelines
   8. Basic Process Window Specifications
   9. Process Requirements
   
   
4. Comprehensive reliability qualification for the lead free component-to-board level interconnection.
   
   
   • Air to air thermal cycle testing
     
     
     • -40 to 125 C
     • Based on joint industry standard JESD22-A104-A
     
     
   • Temperature Humidity Preconditioning of the Components and Board Surface Finishes
     
     
     • 85C, 85% RH
     • 48 hours of exposure
     
     
   • Thermal Cycle and Vibration Testing
     
     
     • Test conditions are to be determined.
   
   
5. On-site process installation, transfer, and documentation for the lead free assembly process.
   
   
6. Hands-on lead free process training on-site.
   
   
7. On-site process consulting support during initial volume production implementation of lead free solder.

DELIVERABLES

• Process documentation on the solderability of Pb-free lead finished components
  
  
  • The solderability screening test results based on dynamic wetting measurements
  • Rank ordering of the solderability of Pb-free lead finishes relative to Sn/Pb lead finishes
  • Confirmation of the Pb-free surface finishes that perform equivalently to Sn/Pb surface finishes over the target process window including substrate surface finish, solder paste material, and reflow profile.
  • Process characterization results of the design of experiments varying the Pb-free lead finishes, board surface finish, paste material type, and solder profile for those Pb-free lead finishes that do NOT perform equivalently to Sn/Pb lead finishes.
  • Effects of the process, board and component variables on solderability of components. Characterization of the solderability results based on X-ray inspection, electrical continuity testing, and Automated Optical Inspection (AOI) of the solder joints, solder fillets, and solder surface finish.
  
  
• Interconnect reliability qualification data for the Pb-free leaded components
• Transfer of the Pb-free lead component finish assembly process using Sn/Pb eutectic solder and process window via a hands-on Technology Transfer Session at Engent's Advanced Assembly Technology Center and documented process.

• Qualified Lead Free assembly process
  
  
  • Process compatibility with a range of SMT components
  • Process qualified for a range of SMT components
  • Printing process capability rating
  • First pass yield and DPMO rating
  
  
• Transfer of the complete Lead Free process and process window via a hands-on Technology Transfer Session at Engent's Advanced Assembly Technology Center
• Complete process documentation in the form of Process Handbooks
  
  
  • Print and Reflow Equipment Process Capability Requirements and Procedures
  • Qualified Materials Specifications based upon Manufacturer and Lead Free Alloy.
  • Design for Manufacturablity Guidelines for lead free processing.
  • Qualified Process Recipe and Parameters
  • Stencil Printing
  • Reflow
  • Inspection
  • Process Installation Guidelines
  • Basic Process Window Specifications
  • Process Requirements
  
  
• Comprehensive interconnect reliability qualification data for the lead free interconnections
• On-site installation and qualification of the lead free assembly process on a specified SMT production line
• On-Site hands-on training of line operators on the lead free process
• Process consulting support for the production launch of a lead free solder product

SUMMARY