Cantilevered Die Ceramic Package for Thermal Stress Isolation
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Solution Overview
Problem
Precision circuits, such as reference voltage supplies, are susceptible to thermal fluctuations and mechanical stress, which can cause them to fall outside their narrow operational parameters, and existing solutions like metal can packages and thermal islands on printed circuit boards have proven inadequate.
Innovation Solution
A ceramic package with a hermetically sealed cavity and a cantilevered semiconductor die, where the precision circuit is suspended above the cavity, using a uniform metal for conductive materials to mitigate thermocouple effects and maximize thermal resistance, thereby protecting the circuit from mechanical and thermal influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the precision circuit is mounted directly on the package substrate, then the device complexity is reduced, but the circuit is exposed to mechanical stress and thermal fluctuations causing it to fall outside narrow operational parameters
Solution Approach 1:
A cantilevered die support structure acts as an intermediary between the package substrate and the precision circuit. This support is isolated from the substrate using a compliant isolation structure, creating a mechanical decoupling that protects the circuit from stress while maintaining electrical connectivity through conductive members.
Solution Approach 2:
The die support structure is segmented into multiple portions with conductive members distributed throughout. This segmentation allows the support to be isolated from the substrate while maintaining electrical pathways, separating the mechanical support function from the electrical connection function.
2Temperature
If conventional metal can packages or thermal islands are used, then thermal management is improved, but thermocouple effects and inadequate isolation from mechanical stress occur
Solution Approach 1:
The package uses uniform metal materials throughout the conductive members and die support structure. This homogeneity eliminates thermocouple effects that would arise from junctions between dissimilar metals, while the isolated cantilevered support structure simultaneously provides thermal management and mechanical stress isolation.
Solution Approach 2:
The compliant isolation structure serves as an intermediary layer between the rigid die support and the package substrate. This intermediary provides mechanical decoupling to eliminate stress transmission while allowing thermal pathways to function, and enables the uniform metal construction to prevent thermocouple effects.
3Ease of manufacture
If the die is rigidly mounted to the substrate, then manufacturing precision is simplified, but mechanical stress is transmitted to the precision circuit
Solution Approach 1:
The compliant isolation structure acts as a mediator between the rigid die support and the package substrate. While the die can be rigidly mounted to the support structure using conventional processes, the isolation layer prevents stress transmission to the circuit, combining manufacturing simplicity with stress protection.
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
The cantilevered die configuration effectively isolates the precision circuit from mechanical and thermal stress, ensuring it operates within specified parameters, particularly beneficial in precision applications like military and space applications.
Implementation Method 1
using a uniform metal for conductive materials to mitigate thermocouple effects
Implementation Method 2
maximize thermal resistance, thereby protecting the circuit from mechanical and thermal influences
Data Source
AI summary
In some examples, a device comprises a ceramic substrate having a cavity, a die pad in the cavity, and a semiconductor die in the cavity and having a first segment coupled to the die pad and a second segment cantilevered over a floor of the cavity. The device also includes a first conductive member in the cavity, the first conductive member coupled to a second conductive member exposed to an exterior of the ceramic substrate. The device also includes a bond wire coupled to a device side of the semiconductor die and to the first conductive member.