Semiconductor Package Layout for Creepage Distance and Oxidation Protection
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Solution Overview
Problem
Semiconductor packages face challenges in maintaining a minimum creepage distance and protecting exposed metal parts from oxidation and corrosion, particularly in applications like the automotive sector, where contamination with metal particles on the molded body surface can negatively impact electrical properties.
Innovation Solution
A semiconductor package design featuring a molded body with electrical contacts on two side faces and metal-free side faces, where the molded body has a cut surface at no more than one side face, and a method involving a leadframe with dummy leads to prevent contamination, followed by coating the electrical contacts to provide oxidation protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the molded body comes into contact with the leadframe during molding, then the manufacturing process is simplified, but metal particles contaminate the molded body surface affecting creepage distance
Solution Approach 1:
The leadframe is segmented into functional components (electrical contacts) and dummy leads. The dummy leads serve as sacrificial elements that are intentionally positioned to contact the molded body, while the electrical contacts are protected from contamination. This segmentation allows the molding process to proceed with leadframe contact while preventing metal particle contamination of the molded body surface.
Solution Approach 2:
The dummy leads act as intermediary elements between the leadframe and the molded body. These dummy leads are specifically designed to contact the molded body during molding, serving as a mediator that prevents direct contact between the electrical contacts and the molded body surface, thereby preventing contamination while maintaining manufacturing simplicity.
2Reliability
If electrical contacts are exposed on side faces, then electrical connectivity is achieved, but oxidation and corrosion occur due to environmental exposure
Solution Approach 1:
A coating is applied to the electrical contacts that creates a protective barrier, effectively creating an inert environment around the exposed metal surfaces. This coating prevents direct contact between the electrical contacts and environmental factors such as oxygen and moisture, thereby preventing oxidation and corrosion while maintaining electrical connectivity.
3Productivity
If metal particles contaminate the molded body surface, then manufacturing is straightforward, but the creepage distance requirement is not met
Solution Approach 1:
The harmful metal particles are extracted from the system by using dummy leads that are intentionally sacrificed. The dummy leads are designed to be the elements that contact the molded body during molding, thereby extracting the contamination risk away from the electrical contacts and the molded body surface, ensuring creepage distance requirements are met while maintaining manufacturing efficiency.
4Strength
If the molded body contacts the leadframe, then structural support is provided, but metal-free side faces cannot be ensured
Solution Approach 1:
The leadframe is segmented into electrical contacts and dummy leads with distinct functions. The dummy leads provide the necessary structural support through controlled contact with the molded body, while the electrical contacts are isolated to maintain metal-free side faces. This segmentation allows structural support to be achieved without compromising the metal-free requirement.
Solution Approach 2:
Different regions of the leadframe are given different properties and functions. The dummy leads are positioned and designed to contact the molded body for structural support, while the electrical contacts are positioned to remain exposed but protected. This local differentiation ensures that structural support is provided where needed while maintaining metal-free side faces where required.
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 ensures reliable creepage distance and oxidation protection by preventing metal particle contamination and ensuring the molded body does not come into contact with the leadframe, thereby maintaining the integrity of electrical properties.
Implementation Method 1
there may be a requirement to protect exposed metal parts of semiconductor packages, e.g. electrical contacts, from oxidation and corrosion due to exposure to environment
Data Source
AI summary
A semiconductor package is disclosed. In one example, the semiconductor package comprises a semiconductor chip, a molded body encapsulating the semiconductor chip and comprising a top face and an opposing bottom face and four side faces connecting the top and bottom faces, and a plurality of electrical contacts arranged on two of the side faces of the molded body, wherein the other two side faces are metal-free side faces, and wherein the molded body comprises a cut surface at no more than one of the side faces.