Semiconductor Package Crack Arrest Features
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Solution Overview
Problem
The increased density of wires in semiconductor devices leads to resin-rich areas in molding compounds with higher thermal expansion and lower strength, causing cracks that can damage the device by separating the ball bond from the semiconductor die.
Innovation Solution
Incorporating molding compound crack stops in the edge seal region to prevent cracks from propagating into the active circuit region, these crack stops are designed to direct cracks vertically and maintain the integrity of the semiconductor device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of wires is increased to add additional circuitry, then the functionality of the semiconductor device is improved, but the spacing between wires decreases causing resin-rich areas with higher CTE and lower strength that lead to cracks
Solution Approach 1:
The patent introduces crack arrest features that segment the molding compound into distinct regions. These features create barriers that divide the continuous resin-rich areas into smaller zones, preventing cracks from propagating across the entire device. The segmentation occurs through structural elements like recesses or variations in the molding compound that interrupt crack paths while maintaining overall device functionality.
Solution Approach 2:
The patent employs an intermediary layer or structure between the wire bonds and the molding compound that acts as a buffer. This intermediary element absorbs or redirects the stress generated by thermal expansion differences, preventing direct stress transmission that would cause cracks. The intermediary serves as a mediator that protects the wire bonds from the harmful effects of resin-rich areas.
2Volume of moving object
If the spacing between wires is decreased to increase circuit density, then the device size is reduced, but the molding compound develops resin-rich areas with decreased strength
Solution Approach 1:
The patent applies local quality by creating regions with different properties within the molding compound. Specifically, it introduces areas with modified filler distribution or composition in response to the resin-rich zones. These localized modifications enhance strength precisely where needed (near wire bonds) without affecting the overall device size or requiring increased spacing between wires.
Solution Approach 2:
The patent utilizes composite materials by combining the molding compound with additional reinforcing elements or filler materials in specific regions. This creates a composite structure where the enhanced material properties provide increased strength to counteract the weaknesses introduced by resin-rich areas, allowing maintain compact device dimensions.
3Quantity of substance
If the filler in the molding compound is blocked by wires, then resin-rich areas are created with higher coefficient of thermal expansion, but this leads to crack formation during temperature changes
Solution Approach 1:
The patent modifies physical or chemical parameters of the molding compound in response to resin-rich areas. This includes adjusting filler size distribution, filler concentration, or material composition in specific regions to change the thermal expansion characteristics. By altering these parameters locally, the patent reduces the harmful thermal expansion stress that would otherwise cause cracks during temperature cycling.
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 effectively prevents cracks from entering the active circuit region, ensuring the semiconductor device's functionality by maintaining the connection between wires and the semiconductor die, even under temperature changes.
Implementation Method 1
one or more molding compound crack stops that are means for preventing cracks that occur in the molding compound from extending into the active circuit region of a semiconductor die
Implementation Method 2
The resin-rich areas have a higher coefficient of thermal expansion (CTE) and a decreased strength than areas with more filler. When exposed to changes in temperatures, a crack is created in the resin-rich area.
Data Source
AI summary
A package device has a package substrate, a semiconductor die on the package substrate, and a molding compound on the package substrate and over the semiconductor die. The semiconductor die has a last passivation layer, an active circuit region in an internal portion of the die, an edge seal region along a periphery of the die, and a structure over the edge seal region extending above the last passivation layer, covered by the molding compound, and comprising a polymer material. The structure may extend at least five microns above the last passivation layer. The structure stops cracks in the molding compound from reaching the active circuit region. The cracks, if not stopped, can reach wire bonds in the active region and cause them to fail.