Package Substrate Protective Layer for Reliable Underfill Flow
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Solution Overview
Problem
Conventional package substrates face reliability issues due to inadequate underfill material injection spaces, leading to increased height and manufacturing costs, and compromised underfill flowability and reliability.
Innovation Solution
A circuit board design with a first protective layer having a structured inner wall with distinct inclinations and curvatures, allowing stable underfill material injection and minimizing overall height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional package substrate structure is used, then the manufacturing process is simple, but the underfill material injection space is insufficient leading to reliability problems
Solution Approach 1:
The first protective layer is segmented into multiple regions (first region, second region, third region) with different inner wall configurations. Each region has specific inclination angles and curvature radii designed to control underfill material flow in different areas, ensuring reliable injection while managing the complexity through functional segmentation.
Solution Approach 2:
Different regions of the first protective layer are assigned different local geometric properties (inclination angles, curvature radii) tailored to their specific functions. The first region has a first inclination angle for initial material entry, the second region has a second inclination angle for material distribution, and the third region has a curvature radius for flow control, creating local quality variations that optimize overall performance.
2Reliability
If the protective layer height is increased to provide injection space, then underfill dispensing is improved, but the overall package substrate height increases
Solution Approach 1:
The third region of the first protective layer incorporates a curved surface with a specific curvature radius, replacing a purely flat or linear structure. This curvature optimizes the underfill material flow path and distribution while maintaining a compact vertical profile, ensuring reliable dispensing without excessive height increase.
Solution Approach 2:
The invention optimizes specific geometric parameters (inclination angles, curvature radii, region dimensions) of the first protective layer to achieve the minimum necessary height for reliable underfill injection. By precisely controlling these parameters, the design provides adequate injection space while minimizing the overall package substrate height.
3Reliability
If material injection space is increased, then underfill flowability is improved, but manufacturing costs increase due to material waste
Solution Approach 1:
The first protective layer is designed with dynamic flow control features including inclined surfaces and curved regions that guide underfill material flow in real-time during the injection process. The varying inclination angles and curvature radii create optimal flow paths that enhance material distribution while preventing excessive spillage and waste.
Solution Approach 2:
The first protective layer acts as an intermediary structure between the underfill material source and the target area. Its specifically designed inner wall geometry (with different inclination angles and curvature radii in different regions) mediates the material flow, controlling distribution and minimizing waste while ensuring adequate flowability for reliable injection.
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
Ensures reliable underfill material dispensing, reduces package substrate height, and minimizes manufacturing costs by optimizing underfill flow and reducing material waste.
Implementation Method 1
the underfill material or the epoxy material can be naturally injected into the opening along the curved surface of the second portion by having the curved surface of the second portion of the first protective layer, and accordingly, the capillary can be maximized
Data Source
AI summary
A circuit board according to an embodiment includes an insulating layer; a circuit pattern disposed on the insulating layer, and a first protective layer disposed on the insulating layer, wherein the first protective layer includes a first opening vertically overlapping at least a part of an upper surface of the circuit pattern; wherein an inner wall of the first protective layer constituting the first opening includes: a first portion having a first inclination, and a second portion disposed on the first portion and having a second inclination different from the first inclination, and wherein the first portion overlaps the circuit pattern in a horizontal direction.