Meeting NEMI Requirements for Tin Whiskers

Mitigation techniques

• The first mitigation technique is the choice of plating.
  • Fairchild has selected pure matte tin plating. The reason for this is matte tin does not use these chemical additives, the grain structure of the matte tin is somewhat larger and it does not have the shiny appearance of bright tin.
• Tin whisker mitigation continues with control of the plating process.
  • Fairchild works with our customers to ensure the purity of the chemicals used in the plating process. Very low levels of impurities, especially carbon and copper, are required. The process is frequently monitored to restrict the impurity levels.
  • The plating processes have been developed to produce uniform plating with relatively large grains, minimizing any intrinsic compressive stress. The minimum plating thickness for all Fairchild products is 8.0µm.
• The last mitigation technique is a one hour bake at 150°C is performed very shortly after the plating is completed.
  • This bake helps to form a more uniform layer of tin-copper intermetallic at the interface between the copper leadframe and the tin plating. This layer of intermetallic has been shown to reduce the potential for tin whisker growth.

NEMI Testing Requirements

• These mitigation techniques have allowed Fairchild to successfully pass the requirements of the NEMI-recommended tin whisker testing.