Exposed Die Power Semiconductor Package Assembly
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Solution Overview
Problem
The existing power semiconductor package assembly process requires two separate die attach steps, one for the power die using solder and another for the control die using adhesive, increasing time and cost, and is prone to contamination and delamination issues due to high-temperature solder reflow.
Innovation Solution
A semiconductor package assembly method using a lead frame with a cavity to mount the power die with a solderless die-attach adhesive, allowing concurrent curing of both dies and eliminating the need for solder paste, which reduces contamination and simplifies the process while maintaining heat dissipation through a solder paste applied post-molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If solder paste is used to mount the power die on the die paddle, then heat dissipation is improved due to the thermal conductivity of solder, but the assembly process becomes more complex and time-consuming due to high-temperature reflow requirements and multiple die attach steps
Solution Approach 1:
The patent changes the mounting method from solder-based to adhesive-based, fundamentally altering the attachment parameter from metallic bonding to polymer bonding. This eliminates the need for high-temperature reflow processes while maintaining adequate thermal management through the adhesive material selection and design
Solution Approach 2:
The patent extracts the solder paste mounting step entirely from the assembly process, removing the complex high-temperature reflow operation. The power die is mounted directly on the die paddle using adhesive, eliminating the intermediate solder layer and associated process complexity while still achieving functional thermal conduction
2Strength
If high-temperature solder reflow is used to mount the power die, then mechanical bonding strength is improved, but contamination and delamination issues occur due to the high temperature exposure
Solution Approach 1:
The patent replaces the durable solder joint with an adhesive bond that achieves sufficient strength for the application without requiring extreme temperatures. The adhesive forms a reliable but simpler bonding interface that avoids the harmful thermal effects of solder reflow
Solution Approach 2:
The adhesive acts as an intermediary material between the power die and die paddle, providing both mechanical bonding and thermal conduction functions. This intermediary layer eliminates the need for direct solder bonding while maintaining adequate performance, and also serves as a buffer that prevents thermal shock-induced delamination
3Manufacturing precision
If two separate die attach processes are used (solder for power die, adhesive for control die), then each die can be optimally mounted, but assembly time and cost increase
Solution Approach 1:
The patent merges the mounting processes for both power die and control die into a single adhesive-based operation. Both dies are mounted using the same adhesive material and curing process, eliminating the need for separate solder reflow and adhesive curing steps. This consolidation maintains mounting quality while significantly reducing assembly time and process complexity
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 reduces the assembly steps, minimizes contamination, and prevents delamination, while ensuring effective heat dissipation, thus improving the efficiency and reliability of the power semiconductor package.
Implementation Method 1
mount the power die with a solderless die-attach adhesive
Implementation Method 2
the solder acts as a heat sink that dissipates heat emitted from the power die
Data Source
AI summary
A semiconductor package has a lead frame and a power die. The lead frame has a first die paddle with a cavity formed entirely therethrough. The power die, which has a lower surface, is mounted on the first die paddle such that a first portion of the lower surface is attached to the first die paddle using a solderless die-attach adhesive, and a second portion of the lower surface, is not attached to the first die paddle and abuts the cavity formed in the first die paddle such that the second portion is exposed.