Component Terminal Finishes Phase 2

Various techniques have been proposed to reduce the Sn-whisker risk with matte Sn finishes. Nevertheless, most end users of electronic still have concerns about long term Sn-whisker growth risk with Sn based terminal finishes. NiPd-based Pre-Plated lead Leadframe (PPF) finishes have been introduced as one Pb-free alternative with no Sn-whisker risk. An improved technology that overcomes the technical limitations of the existing NiPd-based finishes has been developed and applied extensively, but degradation in the Moisture Sensitivity Level (MSL) of a package component due to the limited adhesion quality between compound and noble metal surface and the increase in Pb-free SMT temperature (260℃) has occurred more frequently with NiPd-based finish packages.

Project stage: 
Project type: 

Idea Information

Background: 

Various techniques have been proposed to reduce the Sn-whisker risk with matte Sn finishes. Nevertheless, most end users of electronic still have concerns about long term Sn-whisker growth risk with Sn based terminal finishes. NiPd-based Pre-Plated lead Leadframe (PPF) finishes have been introduced as one Pb-free alternative with no Sn-whisker risk. An improved technology that overcomes the technical limitations of the existing NiPd-based finishes has been developed and applied extensively, but degradation in the Moisture Sensitivity Level (MSL) of a package component due to the limited adhesion quality between compound and noble metal surface and the increase in Pb-free SMT temperature (260℃) has occurred more frequently with NiPd-based finish packages.

Problem: 

Recently, surface roughening technology have been proposed on Pd-PPF to enhance MSL performance, but those technologies were not practical solution because it makes secondary quality problem like excessive resin bleeding, unstable wire bonding, poor solderability and inconsistency in MRT. The previous studies for the improvement of MSL for a leadframe were focused on the development of mold compounds and die attach glue. In particular various surface treatment technologies have been attempted for a normal Cu leadframe so far, However, most of these processes have not been accepted as a standard production process yet, due to the factors such as increased manufacturing costs, reduced assembly quality from surface roughening, limited process capability of surface etching, lack of quality repeatability and limited MSL-1 implementation.

Definition Information

Approach: 
  • Provide MSL, Moisture Sensitivity Level, information of Pb-free solutions because the market needs of high reliability applications such as server, automotive, communication, etc. is increased very much
  • Evaluate MSL performance of Pb-free surface finishes, Matte tin, NiPdAu, NiPdAu-alloy, etc. to give better surface finish choices to the package user group
Factors to Consider – BOM, A/T
  • Leadframe
    • Package thickness, die pad size, down set depth, exposed pad
    • QFP, QFN, SOIC, and/or TSOP
    • At least one with exposed pad
  • Leadframe finish
    • Ag spot, u-PPF, upgrade u-PPF, NiPdAu, Rough surface treatment
    • Mold compound, Die attach-Focus on common BOM and minimize test legs
  • Die – dummy or functional
Factors to Consider – Testing
  • Define stress conditions and MLS testing criteria
  • Pb-free conditions, No Delaminating Criteria (J-STD-020C)
  • Round Robin
    • Try to apply at least two A/T house to assemble parts using define BOM set (s)
    • Try to apply at least two test sites for MLS
    • This defines
      15 ~18 cells x 2 A/T sites x 2 test sites = 60 - 72 lots

 

Key Deliverables
  • Show best practices for MSL-1 at 260C results and degree of reproducibility
  • Validate MSL-1 capability for automotive requirement (MSL-1 at 260C + Thermal Cycle 500 x)
  • Provide package-users and conferences up-to-date MSL information about NiPd plating based components

 

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