Semiconductor Package Protective Layer for Fine Pad Openings
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Solution Overview
Problem
Conventional solder resist layers on circuit boards face challenges in forming small open regions with reduced undercuts, leading to increased tolerance and reduced reliability due to insufficient curing and exposure resolution, which limits miniaturization and integration of semiconductor devices.
Innovation Solution
A semiconductor package with a protective layer having a width of 10 μm to 30 μm open regions and varying surface roughness, formed using a photosensitive film without fillers, reduces undercut formation and improves bonding strength by exposing a resist pattern directly on the protective layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the open region size is reduced to improve I/O performance and circuit density, then the number of terminals increases, but the exposure resolution and curing sufficiency deteriorate, causing undercut formation and reliability reduction
Solution Approach 1:
The patent changes the material composition parameter of the protective layer by using a photosensitive film without fillers, which improves light transmission and exposure resolution, enabling the formation of smaller open regions (10-30 μm) with proper curing and without undercut formation
Solution Approach 2:
The patent addresses the two-dimensional exposure resolution limitation by introducing a third dimension - the vertical profile control through varying surface roughness. The inner surface roughness is controlled to be different from the upper surface roughness, creating a tapered profile that prevents undercut while maintaining small opening dimensions
2Strength
If the protective layer thickness increases to improve protection, then the bonding strength improves, but light transmission to lower regions decreases, causing insufficient curing and undercut formation
Solution Approach 1:
The patent changes the material parameter by eliminating fillers from the photosensitive film, which improves light transmission through the protective layer while maintaining adequate thickness for bonding strength. The filler-free composition allows sufficient UV light penetration for complete curing even in thicker regions
Solution Approach 2:
The patent resolves the thickness-light transmission contradiction by creating a dimensional variation in surface roughness. The inner surface has different roughness than the upper surface, forming a tapered structure that facilitates light transmission to lower regions while maintaining overall layer thickness for bonding strength
3Length of moving object
If the open region width is reduced below conventional limits, then miniaturization is achieved, but the undercut width increases and reliability decreases
Solution Approach 1:
The patent changes the material parameter by using a filler-free photosensitive film that provides superior resolution and controlled etching characteristics, enabling the formation of narrow open regions (10-30 μm) with minimal or no undercut, thereby maintaining reliability even at reduced dimensions
Solution Approach 2:
The patent controls the vertical dimension through surface roughness variation to prevent undercut formation. By making the inner surface roughness different from the upper surface roughness, a tapered profile is created that narrows toward the bottom, eliminating the undercut problem that normally accompanies miniaturized open regions
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 enables miniaturized open regions, reduces undercut occurrence, enhances electrical and mechanical reliability, and improves bonding strength, allowing for higher circuit integration and device mounting capabilities.
Implementation Method 1
when a development process is performed in a state where the lower region of the exposure region is not sufficiently cured
Data Source
AI summary
A semiconductor package according to an embodiment comprises an insulating layer; a pad part disposed on the insulating layer; a protective layer disposed on the insulating layer and including an open region overlapping the pad part in a vertical direction, wherein a width of the open region of the protective layer in a horizontal direction satisfies a range of 10 μm to 30 μm, and a surface roughness of an upper surface of the protective layer is different from a surface roughness of an inner surface of the open region of the protective layer.