Pulse-Modulated IC Output for Post-Assembly Signal Testing
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Solution Overview
Problem
After mold sealing, semiconductor integrated circuits cannot be analyzed for defects or malfunctions since the check pads used for pre-packaging electrical checks are inaccessible, limiting post-assembly analysis and potential defect detection.
Innovation Solution
Incorporating a pulse modulator and output stage in the semiconductor integrated circuit that allows switching between normal and test modes, enabling analysis of internal analog signals by generating and analyzing switching pulses, with minimal cost increase through signal switching configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If check pads are provided on the semiconductor substrate for pre-packaging electrical checks, then electrical characteristics can be checked before assembly, but the check pads become inaccessible after mold sealing, limiting post-assembly analysis
Solution Approach 1:
The output terminal is designed to serve dual purposes: in normal operation mode it outputs main signals for standard circuit function, while in test mode it outputs internal analog signals for post-assembly electrical characteristic checking. This multi-functionality eliminates the need for separate check pads while maintaining both pre-packaging and post-assembly testing capabilities.
Solution Approach 2:
The semiconductor integrated circuit incorporates a mode switching mechanism that dynamically changes the output terminal's function. By switching between normal operation mode and test mode, the same output terminal can adaptively provide different signal types, enabling flexible testing at different stages without physical reconfiguration.
2Reliability
If the number of lead terminals is increased to provide more check pads, then more electrical characteristics can be checked, but the number of lead terminals is limited and cost increases
Solution Approach 1:
The output terminal functions as a universal interface that can output both main signals during normal operation and various internal analog signals during testing. This eliminates the need for additional dedicated check pads and lead terminals, as the same terminal adapts its function based on the operating mode.
Solution Approach 2:
The invention merges the functions of main signal output and test signal output into a single output terminal. By combining these previously separate functions, the design reduces the total number of required lead terminals while maintaining comprehensive electrical characteristic checking capability.
3Ease of repair
If check pads are made accessible after mold sealing, then post-assembly defect analysis becomes possible, but the mold sealing structure prevents access to internal check pads
Solution Approach 1:
The output terminal serves as a universal access point that provides both normal circuit operation signals and test signals. This eliminates the need for separate accessible check pads after assembly, as the same terminal continuously provides testing capability without requiring physical access to internal circuit nodes.
Solution Approach 2:
The output terminal acts as an intermediary that makes internal analog signals accessible after assembly. Instead of requiring direct access to internal check pads, the terminal mediates by outputting internal signals in test mode, allowing external analysis tools to measure internal circuit characteristics through the already-accessible terminal.
Data Source
AI summary
A pulse modulator receives an analog voltage VIN, and generates a pulse signal that is modulated according to the analog voltage VIN. An output stage generates a switching signal at an output terminal according to the pulse signal. A semiconductor integrated circuit is switchable between (i) a normal mode in which a main signal VMAIN to be used in a normal operating mode is input as the analog voltage VIN to the pulse modulator, and (ii) a test mode in which at least one internal analog signal VAUX generated in the semiconductor integrated circuit is input as the analog voltage VIN to the pulse modulator.