Semiconductor Package Insulating Pattern to Prevent UBM Cracking
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Solution Overview
Problem
The outermost insulating layer adjacent to the under-bump metal (UBM) in semiconductor packages tends to crack due to a low degree of curing, leading to reliability issues.
Innovation Solution
A semiconductor package design that includes a lower and upper redistribution layer with inner and outer insulating patterns, where the inner insulating pattern is composed of polybenzoxazole (PBO) with a cyclization rate of 100%, providing enhanced mechanical strength, and the outer insulating pattern is composed of polyhydroxyamide (PHA) or polyimide (PI), with selective heating of the outermost insulating layer to enhance curing and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the outermost insulating layer is cured at low temperature, then the manufacturing process is simpler and energy consumption is lower, but the insulating layer has low mechanical strength and cracks easily
Solution Approach 1:
The insulating layer is divided into two distinct layers: a first insulating layer with high mechanical strength and low dielectric constant, and a second insulating layer that is easily cured. This segmentation allows each layer to fulfill its specific function without compromising the other, resolving the contradiction between strength and curing energy.
Solution Approach 2:
Different regions of the insulating structure have different properties: the first insulating layer provides mechanical strength and electrical performance, while the second insulating layer provides ease of curing and adhesion. This local differentiation of properties allows the system to achieve both high strength and low curing energy consumption.
2Reliability
If the insulating layer is cured completely, then the chemical resistance is improved, but the mechanical strength decreases due to excessive brittleness
Solution Approach 1:
The insulating structure is segmented into two layers with different curing degrees: the first insulating layer is partially cured to maintain flexibility and mechanical strength, while the second insulating layer is fully cured to provide chemical resistance. This segmentation resolves the contradiction between chemical resistance and mechanical strength.
Solution Approach 2:
The curing parameter is differentiated between layers: the first insulating layer is cured at lower temperature or for shorter time to maintain mechanical properties, while the second insulating layer is cured more extensively to achieve chemical resistance. This parameter differentiation resolves the contradiction.
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 enhanced mechanical and thermal properties of the inner insulating pattern reduce cracking near the UBM, improving the reliability and chemical resistance of the semiconductor package.
Implementation Method 1
The cyclization rate of the inner insulating pattern may be higher than the cyclization rate of the outer insulating pattern
Implementation Method 2
selective heating of the outermost insulating layer to enhance curing and prevent cracking
Data Source
AI summary
A semiconductor package includes a frame, a semiconductor chip, a through via, a connection pad, a lower redistribution layer on the bottom surfaces of the frame and the semiconductor chip, a connection terminal on the lower redistribution layer, an encapsulant covering the top surfaces of the frame and the semiconductor chip, and an upper redistribution layer on the encapsulant. The lower redistribution layer includes a lower insulating layer, a lower redistribution pattern, and an under-bump metal (UBM). The upper redistribution layer includes an upper insulating layer, an upper redistribution pattern, an upper via, and an upper connection pad. The lower insulating layer includes an inner insulating pattern surrounding the side surface of the UBM and an outer insulating pattern surrounding the side surface of the inner insulating pattern. The cyclization rate of the inner insulating pattern is higher than the cyclization rate of the outer insulating pattern.