Retronix Blog

Jul 11, 2016

Micro Coil Springs

Current aerospace avionic designs routinely use integrated circuits packaged in BGA format. Unfortunately, the BGA package trades the compliance of leads for the quantity of noncompliant solder balls, which under thermal cyclic loading, severely limits the life of the solder joints.

Micro Coil Springs

One approach to overcome this limitation was to replace the noncompliant balls with more compliant solder columns.

micro coil springs              micro springs

However for temperature extremes and vibration a more robust and reliable solution was sought by NASA.

A long-term human presence in space without the benefit of resupply will require confidence levels not previously required. Due to this and existing reliability data on columns, NASA started investigating other potential flexible interconnects to improve the thermal reliability of ceramic area array packages. Preliminary assembly experiments with springs of various configurations were conducted. As a result of these preliminary experiments, a micro coil spring (MCS) was chosen and introduced into the test program.

The MCSs provide ample flexibility to withstand the shear forces resulting from the CTE mismatch and are much more robust from a handling perspective than high lead columns.

micro coil springs


Improved Reliability

  • Reduced electrical failures due to connection breaks caused by thermal stress
  • >10,00 thermal cycles without failures

Robust, Rugged & Tough

  • Resilient spring interconnect returns to home position
  • High tolerance for temperature extremes, thermal cycling and vibration
  • Improved three-dimensional flexibility versus traditional solder columns
  • Absorbs CTE (Coefficient of Thermal Expansion) mismatch between ceramic substrated and FR4/Polyimide PC Boards


Retronix can now fit these Micro Coil Springs in our UK facility.


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