Package Substrate Molding Compound for Flat Fine-Pitch Wiring
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Solution Overview
Problem
Conventional wafer-level packaging methods face challenges in fabricating fine-pitch wiring redistribution layers due to the need for costly and precise adhesive layers, which increase fabrication costs and hinder surface flatness.
Innovation Solution
A package substrate design featuring a dielectric body with non-overlapping circuit devices and conductive pillars, connected by bonding wires and a redistribution layer, allowing for the use of conventional photolithography to create flat surfaces for fine-pitch wiring without the need for expensive adhesives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photolithography is used to fabricate fine-pitch wiring RDL, then the upper surface must be very flat, but achieving high surface flatness requires costly adhesive layers and slow precise bonding processes
Solution Approach 1:
The patent introduces a molding compound layer that covers the circuit devices and provides a flat upper surface for RDL formation. This adds a dimensional layer (the molding compound) that separates the circuit devices from the RDL formation process, allowing photolithography to be performed on a flat surface without requiring the circuit devices themselves to be at the same height.
Solution Approach 2:
The molding compound acts as an intermediary layer between the circuit devices and the RDL. It provides a flat working surface for photolithography while accommodating circuit devices at different heights below, eliminating the need for expensive adhesive layers to achieve surface flatness.
2Manufacturing precision
If adhesive layers are used to achieve high surface flatness for fine-pitch wiring, then surface flatness is improved, but fabrication cost increases due to costly adhesives and slow precise bonding
Solution Approach 1:
The molding compound layer creates a flat upper surface dimension that is independent of the vertical positions of the circuit devices below. This allows rapid bonding processes to be used for mounting circuit devices at different heights, while the molding compound provides the flat surface needed for subsequent RDL formation by photolithography.
Solution Approach 2:
The circuit devices are mounted on the substrate first at their respective positions, and then the molding compound is formed to create the flat surface. This preliminary mounting allows for faster bonding processes without compromising the eventual surface flatness required for fine-pitch wiring.
3Adaptability or versatility
If circuit devices are mounted at different heights without molding compound, then device placement flexibility is improved, but the upper surface becomes non-flat making fine-pitch wiring difficult
Solution Approach 1:
The molding compound adds a dimensional layer that fills the vertical gaps between circuit devices at different heights and provides a flat upper surface. This allows circuit devices to be placed with flexibility at different positions and heights while still achieving the surface flatness required for conventional photolithography of fine-pitch RDL.
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 reduces fabrication costs by enabling the creation of flat surfaces for fine-pitch wiring without the need for expensive adhesives, facilitating more efficient and cost-effective production of high-density package substrates.
Implementation Method 1
a first bonding wire connecting the second terminal and the third terminal
Data Source
AI summary
This disclosure provides a package substrate and its fabrication method. The package substrate includes: a dielectric body; a first circuit device disposed in the dielectric body, the first circuit device comprising a first terminal and a second terminal at a top of the first circuit device; a second circuit device disposed in the dielectric body, the second circuit device comprising a third terminal at a top of the second circuit device; a first conductive pillar formed in the dielectric body and connected to the first terminal; a first bonding wire connecting the second terminal and the third terminal; and a redistribution layer comprising a first conductive wire formed on the dielectric body, the conductive wire connected to the first conductive pillar.