Current Sensor IC Packaging With Conductive Film Gap Control
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Solution Overview
Problem
Inconsistent connections and gap height differentials in current sensor IC packages due to heating and cooling processes, leading to die tilt and sensitivity drift, are addressed by using a conductive film to connect IC circuit bond pads to the lead frame, which controls gap height and reduces die tilt.
Innovation Solution
A conductive film, such as an anisotropic conductive film (ACF), is positioned between the semiconductor die and the lead frame to ensure consistent electrical connections and uniform gap height, using conductive particles that allow conductivity only in a specific direction, thereby preventing die tilt and enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonds or solder balls are used to connect the semiconductor die to the lead frame, then electrical connections can be established, but inconsistent connections and gap height differentials occur due to heating and cooling processes
Solution Approach 1:
The patent introduces a compressible material layer between the semiconductor die and the lead frame that acts as a mediator to absorb dimensional changes during heating and cooling. This intermediary layer compensates for thermal expansion and contraction, maintaining consistent electrical connections and uniform gap heights throughout the reflow process without requiring precise control of the heating and cooling cycles.
Solution Approach 2:
The patent changes the physical state and properties of the compressible material layer during the heating and cooling process. The material is selected to have specific thermal expansion coefficients and compressibility characteristics that allow it to maintain optimal gap heights and connection pressures throughout the temperature cycles, thereby ensuring connection consistency and gap height uniformity.
2Stability of the object's composition
If the gap height between the semiconductor die and the lead frame is not uniformly controlled, then die tilt occurs, but controlling gap height requires additional manufacturing complexity
Solution Approach 1:
The patent applies different materials with varying compressibility and thickness characteristics to different regions of the lead frame or semiconductor die assembly. This local differentiation allows precise control of gap heights in specific areas to prevent die tilt, while maintaining overall assembly simplicity without requiring complex active control mechanisms.
Solution Approach 2:
The compressible material layer is designed to automatically self-adjust and self-level during the assembly and heating processes. The material's inherent elastic properties enable it to compensate for manufacturing tolerances and prevent die tilt without requiring external control systems, active monitoring, or complex adjustment mechanisms, thereby maintaining manufacturing simplicity.
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
The use of a conductive film ensures consistent electrical connections and reduces die tilt, improving sensitivity and performance consistency in current sensor IC packages.
Implementation Method 1
The conductive film may be conductive in a first direction extending from the die surface to the at least one signal lead and nonconductive in a second direction which is perpendicular to the first direction
Implementation Method 2
The magnetic field sensing element may be configured to sense a magnetic field associated with a current through the primary conductor and generate an output signal indicative of the current
Data Source
AI summary
A current sensor integrated circuit (IC) package is flip-chip bonded using a conductive film to connect the IC circuit bond pads to the lead frame. A conductive film is positioned between the die surface of a semiconductor die and at least one signal lead of the lead frame. The conductive film is conductive in a first direction between the die and the signal lead and nonconductive in other directions. The conductive film is further configured to control a gap height between the die and the lead frame to reduce die tilt, thus improving the sensitivity and performance consistency of the package.