Substrate Grooves for Gas Removal in Chip Packaging
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Solution Overview
Problem
Existing chip packaging methods face challenges in efficiently removing air bubbles during the injection molding process, which can lead to instability due to thermal expansion and affect the connection region on the substrate's back surface.
Innovation Solution
A substrate with grooves open to the exterior on its surface, where the depth is less than the substrate's thickness, allowing for effective gas removal without blocking the connection area, and the groove's width is narrower than the filling material's width to prevent filling and maintain gas removal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air holes are formed in the substrate to remove gas during injection molding, then gas removal efficiency is improved, but the connection region on the back surface of the substrate is reduced and circuit design is hindered
Solution Approach 1:
The gas removal function is segmented from the substrate body by creating grooves on the front surface. These grooves divide the gas removal function into multiple channels that guide gas toward escape paths without requiring holes through the entire substrate thickness, thereby preserving the back surface connection region.
Solution Approach 2:
The solution transitions from a three-dimensional approach (through-substrate air holes) to a two-dimensional approach (surface grooves). By confining the gas removal structures to the front surface plane with controlled depth, the invention eliminates the need for deep penetrating holes that would occupy back surface area, thus resolving the contradiction between gas removal efficiency and connection region preservation.
2Reliability
If the number of air holes is increased to improve gas removal, then more gas removal positions are available, but each air hole becomes smaller and is more prone to blocking by plastic packaging material
Solution Approach 1:
The groove structure provides a dynamic gas removal path where gas can escape through multiple channels formed by the grooves. The grooves are designed with sufficient width to maintain open passages that resist blocking by plastic material while still effectively removing gas during the injection molding process.
Solution Approach 2:
The grooves act as intermediary structures that facilitate gas removal without requiring direct through-holes. By creating surface-level channels that guide gas flow to escape paths, the grooves mediate between the trapped gas and the external environment, preventing plastic material from directly blocking the gas removal paths.
3Reliability
If air holes penetrate through the substrate, then gas can be removed effectively, but the area used for circuit formation is occupied and solder ball distribution is affected
Solution Approach 1:
The gas removal function is extracted from the substrate interior and relocated to the front surface through groove structures. This extraction eliminates the need for through-substrate holes that would interfere with circuit formation and solder ball distribution on the back surface, while still achieving effective gas removal.
Solution Approach 2:
The invention moves the gas removal structures from the vertical dimension (through-substrate holes) to the horizontal dimension (surface grooves). By confining the gas removal function to the front surface plane, the back surface remains fully available for circuit design and solder ball formation, resolving the contradiction between gas removal effectiveness and circuit design simplicity.
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
This approach enhances the reliability of the packaged structure by improving gas removal efficiency while preserving the connection region on the substrate's back surface, ensuring stable chip-substrate bonding and flexible solder ball distribution.
Implementation Method 1
the groove having two ends open to the exterior is formed in the first surface of the substrate to remove gas in the process of forming the bottom filling layer
Data Source
Figure 1~2B
Figure 2C~3B
Figure 4~6
AI summary
The present invention relates to a packaged structure and a forming method thereof. The packaged structure includes: a substrate having a first surface and a second surface opposite to each other, the first surface including at least one strip-shaped groove having two ends extending to edges of the substrate and open to the exterior, with a depth less than the thickness of the substrate; a chip fastened onto the first surface in a flipping manner and electrically connected to the substrate, and at least partially located within the projection of the chip on the substrate; a bottom filling layer filling the gap between the chip and the first surface; and a plastic packaging layer covering the bottom filling layer and packaging the chip. The packaged structure effectively removes the gas inside the packaged structure in the injection molding process without affecting the connection area on the back surface of the substrate.