6-Joyce-Board Test Workshop 2005.pdf

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Definition of <strong>Board</strong> Flexure• When a board is assembled it is stressed—andtherefore strained—in many directions. This“board flexure” puts stress on the solder jointsand causes the package to flex, too. The cornersolder balls are usually under the most stress.BGA PackageRegions ofroughly equalstress4Highest Stressis in the corner• We do not have a way to directly measure thestress or strain on the solder balls, so wemeasure the strain on the PCB near the cornerof the package.
How do we measure strain?• We measure strain using rectangular rosette straingages that measure 3 directions at once. (e1,e2,e3)• They work by measuring the resistance changethat occurs when a metal is strained.e3e2e15
Page 1 and 2: Board Test Workshop 2005Board Flex
Page 3: Intro to Strain testing• As BGA p
Page 7 and 8: Strain Metrics• Since Strain is a
Page 9 and 10: And is less bend mode sensitive•
Page 11 and 12: Strain Limit Determination• Strai
Page 13 and 14: LF Solder vs Tin-Lead Eutectic Sold
Page 15 and 16: Intel® Board Flex InitiativeOvervi
Page 17 and 18: Mobile Components Strain LimitGuida
Page 19 and 20: Test Equipment Requirements• Data
Page 21 and 22: Gage Locations• LGA 775 socket- 2
Page 23 and 24: Demonstration• Flex test run #1
Page 25 and 26: Sample Report25
Page 27 and 28: Gage Locations27
Page 29 and 30: JEDEC 9704• Jedec Spec29
Page 31: Backup31

6-Joyce-Board Test Workshop 2005.pdf

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