IC Card Dielectric Support Layer Fill Material CTE Matching
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Solution Overview
Problem
The thermal mismatch between the mold compound body and the dielectric support layer in IC cards causes high stresses at the bond wire stitch bonds, leading to delamination and failure, due to their differing coefficients of thermal expansion.
Innovation Solution
Incorporating a fill material within the openings of the dielectric support layer with a coefficient of thermal expansion closer to that of the dielectric support layer, rather than the mold compound body, to reduce stress at the IC card contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If mold compound body with lower CTE is used to surround IC die, then thermal stability of IC die is improved, but stress at bond wire stitch bonds increases causing delamination and failure
Solution Approach 1:
The patent introduces a dielectric support layer with intermediate CTE properties between the mold compound body (low CTE) and the IC die/high CTE materials. This intermediary layer acts as a stress buffer that reduces the thermal mismatch stress transmitted to the bond wire stitch bonds, preventing delamination while maintaining the thermal stability benefits of the low CTE mold compound.
Solution Approach 2:
The patent changes the CTE parameter of the support layer to be intermediate between the mold compound and the IC die. By selecting a dielectric support layer with CTE properties that fall between these two materials, the system creates a gradual transition in thermal expansion characteristics, reducing the abrupt stress changes that cause bond wire failure.
2Stress or pressure
If dielectric support layer with higher CTE is used, then stress matching with mold compound is improved, but thermal expansion mismatch with IC die increases causing additional stress
Solution Approach 1:
The patent optimizes the CTE parameter of the dielectric support layer to achieve an intermediate value that balances stress matching with the mold compound while maintaining acceptable thermal expansion compatibility with the IC die. This parameter optimization prevents both delamination at the mold compound interface and excessive stress on the IC die.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces peel stress at the IC card contacts, enhancing the stability of the bond wires and the IC module by matching the thermal expansion of the dielectric support layer, thereby preventing delamination and improving the reliability of the IC card.
Implementation Method 1
The dielectric support layer has a first coefficient of thermal expansion (CTE). A plurality of bond wires are included, and each bond wire extends from a respective bond pad to a corresponding contact through an adjacent opening in the dielectric support layer. A respective body of fill material is within each opening in the dielectric support layer. Each body of fill material has a second CTE. The first CTE is closer to the second CTE than to the third CTE.
Data Source
AI summary
An integrated circuit (IC) module for an IC card includes a plurality of IC card contacts in side-by-side relation. A dielectric support layer is above the contact layer and has a plurality of openings and a first coefficient of thermal expansion (CTE). An IC die is above the dielectric support layer and includes a plurality of bond pads. A bond wire extends from a respective bond pad to a corresponding contact through an adjacent opening in the dielectric support layer. A respective body of fill material is within each opening and has a second CTE. A mold compound body is above the dielectric support layer, the bodies of fill material, and surrounding the IC die. The mold compound body has a third CTE. The first CTE is closer to the second CTE than to the third CTE.