Two-Step Molding for Lead Frame Encapsulation
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Solution Overview
Problem
Integrated circuits used in harsh environments, such as corrosive liquids or ink, face exposure risks due to compatibility issues with traditional printed circuit boards, leading to potential contamination and electrical shorts from fine-pitch metal traces.
Innovation Solution
A two-step insert molding process using thermoplastic or thermoset materials to fully encapsulate pre-molded lead frames, supporting and isolating fine-pitch trace arrays to prevent exposure and electrical shorts, while maintaining ink compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional printed circuit boards are used in harsh environments, then electrical connectivity is provided, but compatibility issues arise leading to corrosion and electrical shorts
Solution Approach 1:
The patent introduces an ink-compatible substrate as an intermediary between the corrosive liquid environment and the fine-pitch metal traces. This substrate acts as a protective barrier that prevents direct contact between the corrosive liquid and the metal traces, eliminating corrosion while maintaining electrical connectivity. The substrate is specifically designed to be compatible with ink and corrosive liquids, thereby resolving the compatibility issue without sacrificing reliability.
2Ease of operation
If fine-pitch metal traces are exposed to corrosive liquids, then electrical signaling is enabled, but contamination and electrical shorts occur
Solution Approach 1:
The patent employs a thin-film encapsulation layer that conformally coats the fine-pitch metal traces. This thin film provides continuous protection over the complex three-dimensional trace structures, preventing contamination and electrical shorts while maintaining the electrical signaling capability. The encapsulation layer is designed to follow the contours of the traces, ensuring complete coverage without interfering with electrical performance.
3Ease of manufacture
If single-step molding is used to encapsulate lead frames, then manufacturing is simplified, but fine-pitch trace arrays are not adequately supported leading to potential damage
Solution Approach 1:
The patent divides the encapsulation process into two distinct steps: first molding the lead frame structure, and then molding the fine-pitch trace arrays. This segmentation allows each molding step to be optimized independently - the first step establishes the robust lead frame structure, while the second step provides precise support and protection for the delicate trace arrays. The segmented approach maintains manufacturing efficiency while significantly improving trace array protection.
4Productivity
If lead frames are used in harsh environments without proper encapsulation, then cost is reduced, but exposure to corrosive environments causes failures
Solution Approach 1:
The patent utilizes composite material structures combining ink-compatible substrates, encapsulants, and metal traces in a integrated assembly. This composite approach provides superior corrosion resistance and environmental protection while maintaining cost-effectiveness through material optimization and manufacturing efficiency. The composite structure allows each material to perform its specialized function - the substrate provides chemical compatibility, the encapsulant provides physical protection, and the metal traces provide electrical conductivity - achieving high reliability without excessive cost.
Data Source
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AI summary
Examples for a two-step insert molding process to encapsulate a pre- molded lead frame (104, 304, 504, 704) are described herein. In some examples, a first circuit component (106, 306, 506) and a first portion of a trace array (110, 310, 510) of the pre-molded lead frame for an integrated circuit (1C) assembly are encapsulated by a first insert molding component (112, 312, 512a, 512b, 712). The trace array connects the first circuit component to a second circuit component (108, 308, 508) of the pre-molded lead frame. A second portion of the trace array is encapsulated by a second insert molding component (114, 314, 514, 714).