Multi-Chip Module Bond Wire Testing via Cross-Channel Circuitry
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Solution Overview
Problem
Multi-channel MCM devices with multiple paths per channel, such as isolated gate driver ICs, face challenges in detecting single path failures, as conventional tests lack reliability and integration with existing test flows, leading to potential field returns and revenue impacts due to undetected inter-die bond wire issues.
Innovation Solution
Incorporating cross-channel test circuitry with switches or logic gates between input pins and functional circuitry to enable both normal and test mode operations, allowing for single bond wire testing and ensuring continuity checks without affecting device functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional noise immunity tests are used to check inter-die bond wires, then testing can be performed, but the test reliability is insufficient and there is no clear boundary between failing and passing devices
Solution Approach 1:
The patent segments the testing process by introducing separate test modes (first test mode and second test mode) that can independently test each bond wire. The coupling circuitry can be configured to test bond wires in different channels separately, allowing precise identification of which specific bond wire is defective, thereby achieving clear pass/fail boundaries and reliable measurement results.
Solution Approach 2:
The patent introduces coupling circuitry as an intermediary component between the input pins and functional circuitry. This coupling circuitry includes test circuitry that can be selectively activated to test bond wires without affecting normal device operation. The intermediary test circuitry provides a dedicated path for testing that separates testing functions from functional operations, improving both reliability and measurement precision.
2Reliability
If X-ray imaging is used to detect inter-die bond wire problems, then bond wire issues can be identified, but the test cost significantly increases and it cannot be integrated into existing test flows
Solution Approach 1:
The patent implements self-service testing where the MCM device tests itself using built-in coupling circuitry and test circuitry. The device can autonomously identify defective bond wires through electrical continuity testing without requiring external X-ray imaging equipment. This self-testing capability integrates seamlessly into existing test flows and dramatically reduces test costs while maintaining reliable defect detection.
Solution Approach 2:
The patent replaces the mechanical/optical X-ray imaging system with an electrical testing system. Instead of using X-rays to visually detect bond wire issues, the invention uses electrical continuity testing through coupling circuitry to detect open circuits in bond wires. This substitution of electrical testing for optical/mechanical imaging reduces cost and enables integration into standard electrical test flows.
3Reliability
If additional test circuitry is added for bond wire testing, then testing capability is improved, but device complexity increases
Solution Approach 1:
The patent designs the coupling circuitry to serve multiple functions: it acts as signal coupling elements during normal device operation and as test circuitry when activated in test modes. This multi-functionality allows the same hardware components to perform both functional operations and bond wire testing, improving reliability without proportionally increasing device complexity.
Solution Approach 2:
The patent introduces dynamic configurability where the coupling circuitry can switch between different operational states (normal mode and test modes). The test circuitry can be selectively activated or deactivated based on whether testing is required, allowing the device to adapt its configuration. This dynamic behavior enables testing capability while maintaining operational simplicity during normal use.
Data Source
AI summary
A multichip module (MCM) device include a first die including functional circuitry bonded by a plurality of inter-die bond wires (bond wires) to a second die having functional circuitry. A first channel (Channel A) and second channel (Channel B) each have separate top and bottom signal paths (signal paths) including one of the bond wires. A failure of any of the signal paths does not affect functionality of the device. The first die includes input pins including a first input pin (P1), a second input pin (P2), and coupling circuitry including cross-channel test circuitry positioned between the input pins and the functional circuitry. The coupling circuitry provides for Channel A and Channel B a first configuration for normal mode operation and a second configuration for test mode operation for single bond wire testing for checking continuity of any of the bond wires.