Selective Edge Metallization for Hermetic Cover Lid Seal Rings
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Solution Overview
Problem
Hermetically sealed electronic packages face issues such as metallization errors, outgassing, and solder-related defects like voids and delamination due to the use of soft solder and organic content in metallized layers, leading to weakened seals and potential leak failures.
Innovation Solution
A method involving a polyamide mask applied to a plate to define a central and peripheral area, followed by metallization of the peripheral area and sidewall to form a continuous seal ring, with a solder preform attached via tack welding, using materials like beryllium-copper, molybdenum, or ceramics, and metals like silver, palladium, or gold, to enhance seal integrity and reduce defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If soft solder is used for hermetic sealing, then sealing can be performed at low temperature, but solder voids, dewetting, splatters, and PIND failures occur
Solution Approach 1:
The patent changes the soldering method from traditional soft soldering to friction stir welding, fundamentally altering the process parameters including temperature, pressure, and mechanical action to eliminate solder-related defects while maintaining hermetic sealing capability
Solution Approach 2:
The patent replaces the thermal-mechanical soldering process with a mechanical friction stir welding process, using mechanical energy to create metallurgical bonds without the harmful effects of solder melting and solidification
2Ease of manufacture
If metallized layer is applied to enable soldering, then bonding is enabled, but mask offset and metallization width variation occur
Solution Approach 1:
The patent removes the metallized layer and mask entirely from the process, replacing them with a mechanical welding interface that directly bonds the cover lid to the substrate without requiring peripheral metallization
Solution Approach 2:
Instead of metallizing the peripheral area to enable bonding, the patent inverts the approach by creating a metallurgical bond through mechanical friction stir welding at the interface, eliminating the need for mask-based metallization
3Ease of manufacture
If metallized layer is applied to enable soldering, then bonding is enabled, but metallized layer pulls back from edges creating gaps
Solution Approach 1:
The patent removes the metallized layer that causes pullback and gap formation, replacing it with a mechanical welding interface that ensures continuous contact and bonding without the defects associated with metallized layer adhesion
Solution Approach 2:
The friction stir welding process performs preliminary mechanical and thermal action at the bonding interface to ensure proper material flow and metallurgical bonding before final sealing, preventing gap formation
4Ease of manufacture
If organic content is present in metallized layer, then metallization is achieved, but outgassing occurs
Solution Approach 1:
The patent removes the metallized layer containing organic content entirely, replacing it with a mechanical welding process that creates bonds without introducing organic materials that would outgas
Solution Approach 2:
The friction stir welding process creates a controlled environment at the bonding interface that prevents contamination and outgassing, maintaining a clean metallurgical bond free from organic decomposition products
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
This approach minimizes metallization errors, reduces outgassing, and improves seal strength, leading to increased yield and shelf life of cover lids, while allowing for various solder types and reducing PIND failures, thus enhancing the reliability of hermetic seals.
Implementation Method 1
A polyamide mask is applied to a central area of a first surface of a plate
Implementation Method 2
The peripheral area and the sidewall of the plate are metallized to form a seal ring
Implementation Method 3
A solder preform can then be attached to the seal ring, for example by tack welding
Data Source
AI summary
A cover lid for use with a semiconductor package is disclosed. First, a polyamide mask is applied to one surface of the lid plate. Next, the exposed areas of the surface, as well as the sides of the lid plate, are metallized. The polyamide mask can then be removed. This reduces pullback and shrinkage of the metallized layer, while lowering the manufacturing cost and process times.