Redistribution Pad Surface Structure for Smear-Free Bump Bonding
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Solution Overview
Problem
Current semiconductor package manufacturing processes face challenges in achieving reliable connections between the pad and connection bumps due to smear issues, which can lead to discoloration of encapsulants, peeling of protective layers, and complexity in the manufacturing process.
Innovation Solution
A semiconductor package design featuring a redistribution substrate with a pad having a recess surface and an edge surface, where the recess surface has regular depressions and protrusions, and the edge surface has irregular depressions and protrusions, is created. This design uses a laser beam with a pulse width of less than picoseconds to form openings in the protective layer, removing smear and enhancing connection reliability without a chemical desmear process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pad structure without differential surface treatment is used, then the manufacturing process is simpler, but connection reliability between pad and connection bumps deteriorates due to smear issues
Solution Approach 1:
The pad structure applies different surface treatments to different regions: the recess surface receives a first surface treatment (e.g., chemical etching or plasma treatment) while the edge surface receives a second surface treatment (e.g., mechanical roughening or different chemical treatment). This local differentiation improves connection reliability by optimizing each surface for its specific function while maintaining overall structural integrity.
Solution Approach 2:
The pad surface is segmented into distinct regions (recess surface and edge surface) with different treatments. This segmentation allows each region to be optimized independently for its specific role in the connection process, resolving the contradiction between reliability and complexity by making the complexity functional rather than arbitrary.
2Reliability
If a chemical desmear process is used to remove smear, then connection reliability improves, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
The pad structure is designed with pre-formed recess and edge surfaces that have different surface properties before the bump formation process. This preliminary surface preparation eliminates or reduces the need for subsequent chemical desmear processes, thereby improving connection reliability while maintaining manufacturing simplicity.
Solution Approach 2:
The invention replaces chemical desmear processes with a mechanically formed pad structure featuring differential surface treatments. The recess and edge surfaces are created through mechanical or physical means during pad formation, substituting chemical processes with structural design to achieve the same reliability improvement.
3Reliability
If the pad surface is made highly rough to improve connection, then connection reliability improves, but the protective layer becomes more prone to peeling
Solution Approach 1:
Different regions of the pad surface are treated differently: the recess surface is made rough to enhance connection reliability, while the edge surface maintains a treatment that ensures protective layer adhesion. This local quality differentiation resolves the contradiction by allowing high roughness where needed for connection while maintaining stability where needed for protective layer bonding.
Solution Approach 2:
The pad surface is segmented into functional zones with different roughness levels and treatments. The recess surface segment provides high roughness for connection reliability, while the edge surface segment provides optimized treatment for protective layer stability, eliminating the need to choose between the two conflicting requirements.
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 improves connection reliability between the pad and connection bumps, simplifies the manufacturing process, and prevents issues like discoloration and peeling, resulting in a more robust and efficient semiconductor package.
Implementation Method 1
irradiating the protective layer with a laser beam having a pulse width for less than picoseconds to form an opening exposing at least a portion of the first surface
Data Source
AI summary
A semiconductor package including a redistribution substrate having lower and upper surfaces, the redistribution substrate including a pad on the lower surface, the pad having a first surface and a second surface, and a redistribution layer electrically connected to the pad; a semiconductor chip on the upper surface of the redistribution substrate and electrically connected to the redistribution layer; an encapsulant encapsulating at least a portion of the semiconductor chip; and a protective layer on the lower surface of the redistribution substrate and having an opening exposing at least a portion of the first surface of the pad, wherein the portion of the first surface exposed through the opening includes a recess surface including regular depressions and protrusions and being depressed inwardly toward the second surface, and an edge surface including irregular depressions and protrusions and having a step difference with respect to the recess surface.