Tapeless Leadframe Package for Exposed Sensor Die Assembly
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Solution Overview
Problem
The existing quad-flat no-lead (QFN) integrated circuit packages face challenges in exposing the integrated circuit die, such as die cracking, mold flashing covering sensors, and high fabrication costs due to the transfer molding process and bond wire connections.
Innovation Solution
A tapeless leadframe package is developed with etched protrusions and plating layers to support the integrated circuit die in flip-chip orientation, allowing for mechanical and electrical attachment without covering environment sensors, and a transfer molding process that encapsulates the die and protrusions without sealing the sensor area, followed by etching to define leads and die support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a transfer molding process with spring loaded insert is used to form an opening in the encapsulating body, then the integrated circuit die can be exposed, but die cracking occurs
Solution Approach 1:
The patent removes the spring loaded insert from the molding process entirely. Instead, the encapsulating body is formed with an exposed area through direct molding, eliminating the extraction mechanism that causes die cracking while still achieving the goal of exposing the integrated circuit die for sensor access
Solution Approach 2:
The molding tool is designed with a cavity that pre-defines the exposed area configuration before molding begins. This preliminary design of the mold cavity ensures the encapsulating body is formed with the correct exposed area geometry, eliminating the need for post-molding mechanical extraction that causes damage
2Manufacturing precision
If a transfer molding process with spring loaded insert is used to form an opening in the encapsulating body, then the integrated circuit die can be exposed, but mold flashing covers the optical sensor
Solution Approach 1:
The patent eliminates the spring loaded insert mechanism that causes mold flashing. By using direct molding to form the encapsulating body with the exposed area, the harmful flashing that would cover and damage the optical sensor is completely removed
Solution Approach 2:
The patent uses a standard molding process without specialized spring loaded inserts or complex tooling modifications. This simpler, more robust approach avoids the flashing issue entirely while maintaining sensor exposure, trading the complexity of specialized tooling for process reliability
3Reliability
If bonding wires are used to connect the integrated circuit die to the leadframe, then electrical connection is achieved, but package thickness is limited
Solution Approach 1:
The patent replaces the bonding wire mechanical connection system with a direct flip-chip mounting approach. The integrated circuit die is mounted face-down with bonding pads directly connected to the leadframe through the encapsulating body, eliminating the need for wire bonds and reducing package thickness
Solution Approach 2:
The patent transitions from a wire-bond architecture where connections extend vertically above the die to a flip-chip architecture where connections are made through the die substrate itself. This dimensional reorganization allows for thinner packages while maintaining electrical connectivity
4Manufacturing precision
If a transfer molding process with dedicated mold tooling is used, then the integrated circuit die can be exposed, but fabrication cost increases
Solution Approach 1:
The patent designs the encapsulating body mold cavity to serve multiple functions: it forms the protective encapsulating material, defines the exposed area for sensors, and creates the overall package structure. This multi-functional approach eliminates the need for specialized spring loaded inserts or separate operations, reducing tooling cost and complexity
Solution Approach 2:
The patent uses a standard, simple molding tool design without expensive spring loaded inserts or complex mechanisms. The mold cavity directly forms the exposed area, eliminating the need for costly specialized tooling while achieving the same functional result
Data Source
AI summary
A first side of a tapeless leadframe package is etched to form a ring shaped protrusion and a lead protrusion extending from a base layer. An integrated circuit die is mounted to tapeless leadframe package in flip chip orientation with a front side facing the first side. An electrical and mechanical attachment is made between a bonding pad of the integrated circuit die and the lead protrusion. A mechanical attachment is made between the front side of the integrated circuit die and the ring shaped protrusion. The integrated circuit die and the protrusions from the tapeless leadframe package are encapsulated within an encapsulating block. The second side of the tapeless leadframe package is then etched to remove portions of the base layer and define a lead for a leadframe from the lead protrusion and further define a die support for the leadframe from the ring shaped protrusion.