ON SEMICONDUCTOR TIN WHISKER REPORT

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ON Semiconductor 5005 East McDowell Road Phoenix, AZ 85008 http://onsemi.com

Confidential and Proprietary Information

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ON SEMICONDUCTOR TIN WHISKER REPORT

Introduction

This report is for an evaluation completed in October, 2005 to measure tin whisker growth on a copper alloy leadframe package assembled at ON Semiconductor’s Carmona, Philippines assembly site.

Sample Details Package type: SOIC8

Leadframe material: Cu alloy Plating: Matte tin, 11µ thickness

Anneal: 1 hour at 150°C within 24 hours of plating

Samples were taken from one assembly lot plated in February, 2005.

The SOIC8 package is representative of the leadframe/plating combination at this assembly site and has the worst-case lead bend angles of the packages assembled there.

Testing

Two preconditioning treatments were used:

- none

- Pb-free reflow profile (3 passes with a peak temp of 260°C)

Three test conditions were used:

- Temp Cycle (-55/85°C) for 3000 cycles (inspections at 1000 cycle intervals) - Storage at 60°C/87%RH for 4000 hours (inspections at 1000 hour intervals) - Storage at 30°C/60%RH for 4000 hours (inspections at 1000 hour intervals)

Inspection

Five units and three leads per unit (entire front and sides) were inspected by SEM at each inspection point. The same units were inspected at each interval. The maximum whisker length for each lead inspected was noted. Whiskers were only noted if they were >10µ in length and had an aspect ratio of >2 (length to width).

All initial whisker length measurements were taken by adding the various whisker segments. Whiskers were then re-measured using the measurement technique as defined in JEDEC standard JESD201 (straight line from surface to furthest point of the whisker).

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Results

Results for maximum observed whisker length at each interval are shown in the tables below.

Initial measurements

MAXIMUM WHISKER LENGTH

Precondition 30°C/60%RH (hours) 60°C/87%RH (hours) Temp Cycles 1000 2000 3000 4000 1000 2000 3000 4000 1000 2000 3000 Pb-free none none none none none none 20µ 40µ 28µ 23µ 39µ None none none none none none none 33µ 40µ 38µ 39µ 40µ

After re-measurement

MAXIMUM WHISKER LENGTH

Precondition 30°C/60%RH (hours) 60°C/87%RH (hours) Temp Cycles 1000 2000 3000 4000 1000 2000 3000 4000 1000 2000 3000 Pb-free none none none none none none 15µ 28µ 15µ 18µ 34µ None none none none none none none 30µ 38µ 36µ 35µ 32µ

“none” indicates no whiskers >10µ were found.

3000 temp cycles, Pb-free preconditioning 3000 temp cycles, no preconditioning

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4000 hours 60°C/87%RH, Pb-free preconditioning 4000 hours 60°C/87%RH, no preconditioning

Conclusions

ON Semiconductor’s pass criteria is 45µ maximum length for temperature cycling and 40µ maximum for the storage test conditions. All test results pass these criteria.

The results of this evaluation are applicable to all copper based leadframe packages at this assembly site.

Additional whisker testing is being conducted and this report will be updated accordingly.