Pb-Free option of SRAMs

Version 1
    Question:

    What are the differences in reflow/assembly process required by Pb-Free devices?

     

    Answer:

    There are requirements and conditions for the Pb-Free devices reflow process and are tabulated in the Cypress Pb-Free reflow profile shown below. The product must meet two stringent requirements, zero lead and high temperature (260 ?C) reflow capability. Higher temperature reflow capability is needed because Pb-Free solder pastes melt at higher temperatures. The Pb-Free devices are marked with an 'X' on the package in the standard parts number.

    For leadframe-based packages, Nickel Palladium Gold (Ni-Pd-Au) and Matte Tin (Sn) are the primary options. Nickel Palladium Gold (Ni-Pd-Au) for internally manufactured product and Tin (Sn) for subcontract manufactured products.

    BGA packages will use Tin-Silver-Copper (SnAgCu) instead of Tin-Lead (SnPb) balls 

    Cypress Semiconductor 260 Pb-Free Reflow Profile 

                                                                                                                        
       

    PROFILE ELEMENTS

      
       

    IR - INFRA RED REFLOW

      
       

    Ramp Rate 217 ?C

      
       

    3 ?C /sec max 

      
       

    Preheat Temperature 150 ?C (+/-25?C)

        

     

      
       

    60 to 120 seconds max 

      
       

    Time 50 ?C to Peak Temperature 

      
       

    3.5 minutes, 6 seconds max 

      
       

    Temperature maintained above 217 ?C 

      
       

    60 to 150 seconds 

      
       

    Time within 5 ?C of actual peak

        

    temperature 

      
       

    10 to 20 seconds 

      
       

    Peak temp range

      
       

    260 ?C (-5/+0) ?C 

      
       

    Ramp-down rate 

      
       

    6 ?C /second max