Liquid Crystal Polymer Circuit Package with Mechanical Interlock
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional circuit packages face challenges in withstanding high die-attach temperatures and maintaining hermeticity without using adhesives, often resulting in imperfect seals and reduced thermal and electrical conductivity.
Innovation Solution
A low piece-count circuit package design featuring a flange, frame, and leads with mechanical retention features and specific material compositions that match coefficients of thermal expansion, allowing for a hermetically sealed air cavity without adhesives, enhanced thermal and electrical conductivity, and improved mechanical integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional plastic frames are used in circuit packages, then manufacturing cost is reduced, but the frames cannot withstand high die-attach temperatures and deform
Solution Approach 1:
The patent changes the material parameters by using liquid crystal polymer (LCP) instead of conventional plastics. LCP has a higher glass transition temperature and maintains structural integrity at die-attach temperatures (typically 200-300°C), while still being manufacturable through injection molding processes. This parameter change resolves the contradiction by enabling temperature tolerance without sacrificing ease of manufacture.
Solution Approach 2:
The patent employs composite material structures where the LCP frame is combined with metal flanges and ceramic substrates. The frame material itself may contain fillers or reinforcements that enhance thermal stability. This composite approach allows the plastic frame to withstand high temperatures while maintaining cost-effectiveness compared to fully ceramic or metal packages.
2Temperature
If ceramic frames are used to withstand high temperatures, then temperature tolerance is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent uses LCP frames that are cheaper than ceramic alternatives while providing sufficient temperature tolerance for the application. The frame is designed to be disposable or single-use in the context of the complete package assembly, eliminating the need for expensive ceramic materials that would provide marginal additional temperature resistance beyond what LCP can deliver.
Solution Approach 2:
By changing from ceramic to LCP material, the patent achieves an optimal balance between temperature tolerance and cost. The LCP's thermal properties are sufficient for most die-attach applications, making the expensive ceramic material unnecessary. This parameter change in material selection resolves the cost-temperature tolerance contradiction.
3Device complexity
If adhesives are used to attach the frame to the flange, then assembly is simplified, but hermeticity is compromised with imperfect seals
Solution Approach 1:
The patent replaces the chemical bonding mechanism (adhesives) with a mechanical interlocking system. The frame includes integrated retention features such as clips, tabs, or snap-fit structures that mechanically secure the frame to the flange and encapsulate the die. This mechanical substitution eliminates adhesive-related hermeticity issues while maintaining assembly simplicity.
Solution Approach 2:
The patent merges the frame's structural and sealing functions into a single integrated component. The frame itself forms the hermetic seal through precise molding and mechanical interference fits with the flange and lid, eliminating the need for separate adhesive layers. This merging of functions achieves both assembly simplicity and reliable hermeticity.
4Adaptability or versatility
If separate components (flange, frame, lid) are inventoried and assembled separately, then manufacturing flexibility is improved, but production time and complexity increase
Solution Approach 1:
The patent merges the flange and frame into a single integrated component manufactured as one piece, eliminating the need for separate assembly steps. This integration maintains manufacturing flexibility for different die configurations while dramatically reducing assembly time and complexity. The integrated design allows the complete package to be molded in a single injection molding cycle.
Solution Approach 2:
The integrated flange-frame structure serves multiple functions simultaneously: mechanical support, thermal conduction, electrical isolation, and hermetic sealing. This multi-functionality reduces the number of components and assembly steps while maintaining the flexibility to accommodate different die sizes and configurations through modular design variations.
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 solution provides a cost-effective, high-temperature tolerant circuit package with improved hermeticity, electrical, and thermal conductivity, and mechanical integrity, reducing the need for adhesives and inventory of separate components.
Implementation Method 1
thermoplastic material... capable of withstanding temperatures associated with attachment of the die to the flange
Implementation Method 2
The frame material and the flange material have a coefficient of thermal expansion that closely matches
Implementation Method 3
The frame and the lid encapsulate the die and bonding wires and protects them against intrusion of water vapor and other atmospheric gases
Data Source
AI summary
A circuit package for housing semiconductor or other integrated circuit devices (“die”) includes a high-copper flange, one or more high-copper leads and a liquid crystal polymer frame molded to the flange and the leads. The flange includes a dovetail-shaped groove or other frame retention feature that mechanically interlocks with the molded frame. During molding, a portion of the frame forms a key that freezes in or around the frame retention feature. The leads include one or more lead retention features to mechanically interlock with the frame. During molding, a portion of the frame freezes in or adjacent these lead retention features. The frame includes compounds to prevent moisture infiltration and match its coefficient of thermal expansion (CTE) to the CTE of the leads and flange. The is frame is formulated to withstand die-attach temperatures. A lid is ultrasonically welded to the frame after a die is attached to the flange.