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Standard for Whisker Acceptance Level in Pb-free Lead Finish. A Step towards Green Packaging for Consumer Products to Drive Future European Strength PROTIN

Objective

Wireless products are a key driver for EU microelectronics. Pushed by Japanese companies green consumer products are a must in the near future. To achieve a competitive advantage for EU companies, a fast introduction of Pb-free products especially in the mobile market is required. In this project the 3 main EU semiconductor manufacturers combine their strength to explore a solution for the challenging problem of post-mold plating, which will cover also the majority of future microelectronic packages. In contrast to Japanese companies, EU companies favour Sn over SnBi. One reason is the recycling cost. But whisker formation in Sn-based lead finish is a troublesome and severe problem. The target of this project is to create an industrial acceptable standard for plating inspection to deal with whisker. This standard obtained by explorations will include acceleration test strategies and release criteria for plating surfaces.

Objectives:
In this project the 3 main European semiconductor companies combine their strength to provide Pb-free products especially for the consumer market like mobile devices as soon as possible to push the European microelectronics industry to a leading position in environmental protection and recycling. Most EU companies, from system supplier to board supplier, see Sn as the future plating material for leadframes, a different approach to Japanese companies, that favour SnBi.

The objectives of this project are:
i) to define methods to accelerate whisker tests in pure Sn,
ii) to identify countermeasures to prevent or minimise whisker formation,
iii) work out a standard for whiskers on electroplated finishes, which includes a classification for whisker, failure catalogue, acceptance criteria and methods for inspection.
The final objective of this proposal is to propose an industry acceptable standard that will be filed in the relevant standardisation councils.

Work description:
In the beginning a detailed definition phase of the project is required to have the same wording, equal test methods and parameters. In order to identify project targets a comprehensive overview of the current test methods and knowledge will be prepared. Based on the available knowledge appropriate test parameters must be identified.
These will include
i) material parameters (base material, electrolytes for finish and underlayer),
ii) process parameters (preprocessing/activation, deposition, postprocessing),
iii) properties of the layer and
iv) countermeasures using underlayers and/or applying postprocessing steps.
The 3 project partners will identify individual packages for every company and one in common for correlation purposes. From these packages a representative selection of all materials and geometries for the semiconductor industry will be derived. Each company will assemble these test packages and produce the layers in the way as fixed in the definition phase. A detailed characterisation of the deposits and initial inspection (e.g. microscope, REM) is required to evaluate differences between the deposits according to the applied parameters and to avoid artefacts in later inspection intervals. After application of postprocessing steps (where applied) the samples will be stored in different defined conditions and in ambient conditions for correlation. Sequential inspection and documentation of whiskers will lead to a correlation of growth speed in all storage conditions. This sequential inspection will be done over a period of at least two years, which is the minimum guaranteed storage time of semiconductor components. From these explorations, acceleration tests will be derived. The result will be a proposal for industrial acceptable standardised test methods of lead-free plating in terms of whisker formation and the acceptance criteria of such a plating.

Milestones:
The major milestones of this project will be:
i) Definition of methods to accelerate whisker tests,
ii) Determination of countermeasures to prevent or minimize whisker formation,
iii) set up of a standard for whiskers on electroplated finishes, which includes classification for whisker, failure catalogue, acceptance criteria and inspection methods. The overall result of this proposal is to explore a way to remove Pb from leadframe packages, with focus on portable devices.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

INFINEON TECHNOLOGIES AG
Address
St. Martin Strasse 53
81609 Muenchen
Germany

Participants (2)

PHILIPS SEMICONDUCTORS B.V.
Netherlands
Address
Professor Holstlaan 4
5656AA Eindhoven
STMICROELECTRONICS SA
France
Address
29 Boulevard Romain Rolland
92120 Montrouge