De-packaging Small Outline Transistor Packages for Die Testing
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Solution Overview
Problem
Small Outline Transistor (SOT) packages are difficult to debug due to the challenge of accessing the die within the package, particularly the back surface, which is electrically grounded, making it hard to test and evaluate the underlying circuitry effectively.
Innovation Solution
A method involving the removal of molding compound, etching of the die attach pad, and forming an ohmic contact on the back surface to ground the die, allowing for proper electrical testing and debugging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the die attach pad is removed to access the back surface of the die, then accessibility for testing is improved, but the die can no longer be properly grounded causing circuitry to malfunction
Solution Approach 1:
The patent segments the die attach pad removal process by selectively removing only the pad material while preserving the underlying ground lead connection. This allows the back surface to be accessible while maintaining the electrical ground path through the lead frame, resolving the contradiction between accessibility and grounding reliability.
Solution Approach 2:
The patent introduces an intermediary ground lead connection that mediates between the removed die attach pad and the die back surface. By establishing a new ground connection through the lead frame to the die back surface, the patent maintains proper grounding while enabling access to the circuitry.
2Volume of moving object
If the SOT package size is kept small for miniaturization, then device compactness is improved, but accessibility to the die for debugging becomes difficult
Solution Approach 1:
The patent extracts the die from its original encapsulated position by selectively removing the molding compound and die attach pad materials. This extraction process creates access to the die back surface while preserving the compact overall package structure, resolving the contradiction between miniaturization and accessibility.
Solution Approach 2:
The patent applies local quality changes by selectively removing materials only in specific areas (molding compound over the die, die attach pad) while leaving the rest of the compact package structure intact. This localized modification enables access to the die back surface without increasing the overall package volume.
3Adaptability or versatility
If multiple levels of metal interconnect and dielectric layers are present on the die, then circuit functionality is improved, but accessibility to underlying circuitry becomes difficult
Solution Approach 1:
The patent inverts the conventional approach of accessing circuitry from the top surface through multiple interconnect layers. By removing the die attach pad and accessing the die back surface, the patent provides direct access to the underlying circuitry and ground connections, eliminating the need to navigate through multiple metal and dielectric layers.
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
Enables effective electrical testing and debugging of SOT package circuitry by grounding the die, overcoming the accessibility issues and ensuring the circuitry operates correctly.
Implementation Method 1
An etching solution is subsequently introduced through an opening in the mask to etch away the die attach pad
Implementation Method 2
An ohmic contact is then formed on the exposed back surface of the die. The ohmic contact is used to ground the die so that the electrical circuitry on the device will operate properly
Data Source
AI summary
A method to de-packaging a semiconductor device to access and test the die within the package. The method involves initially removing molding compound from a first surface of the package to expose the underlying die attach pad of the package. A mask is then formed over the die attach-pad. An etching solution is subsequently introduced through an opening in the mask to etch away the die attach pad. Once the etching is complete, the die attach film is removed. An ohmic contact is then formed on the exposed back surface of the die. The ohmic contact is used to ground the die so that the electrical circuitry on the device will operate properly. Once grounded, the circuitry on the die can be electrically tested and debugged.