Keysight LPDDR4, Installation Manual

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4 Interposers and Riser Soldering Guidelines
36 Keysight W6600A-series LPDDR4 BGA Interposers Installation Guide
Interposer Fabrication Notes
Operating Environment
The W6600A-series interposers are constructed of polyimide material that supports solder
attachment of the interposer using the higher temperatures required by a lead-free solder process.
The coefficient of thermal expansion for the interposer is 55 ppm/degree C. When operating in a
soldered-down environment over a wide range of temperatures, the expansion coefficient of the
interposer, DRAM, and system being probed must be matched to avoid stress related failure of the
solder connections between the Interposer and attached components. The interposer material allows
operation over an industrial temperature range of -40 to +85 degrees Celsius (non-condensing),
subject to the above constraint.
Mechanical Dimensions
When a W6600A-series interposer is soldered to a riser, flatness must be maintained on the order of
3.5 mils or less across the BGA footprint to maximize successful soldering to the interposer.