Coreless Packaging Substrate Fabrication via Carrier Removal
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Solution Overview
Problem
Conventional coreless packaging substrates face warpage issues due to stress accumulation from cutting processes and cannot be reused, leading to reduced product yield and increased fabrication costs.
Innovation Solution
A method involving forming an inner built-up circuit board on a carrier, removing the carrier, and symmetrically constructing outer built-up structures on both sides of the inner board to offset stresses, while using carriers with varying bonding forces to facilitate repeated use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the carrier is cut after the built-up structure is formed on the carrier, then the coreless packaging substrate can be fabricated, but great stresses accumulate causing warpage of the packaging substrate
Solution Approach 1:
The built-up structure is formed on the carrier before the carrier cutting step. By performing the building-up process preliminary, the stress accumulation is managed during subsequent carrier removal and cutting operations, preventing warpage of the finished packaging substrate.
Solution Approach 2:
The carrier serves as an intermediary substrate that supports the built-up structure during fabrication. The carrier is designed with specific bonding characteristics (bonding force between carrier and built-up structure is greater than bonding force between carrier and release layer) to enable controlled separation and stress management during the fabrication process.
2Productivity
If the carrier is cut after the built-up structure is formed, then the coreless packaging substrate is obtained, but the carrier cannot be repeatedly used increasing fabrication cost
Solution Approach 1:
The carrier is designed to be recoverable and reusable. The specific bonding force relationship allows the built-up structure to be separated from the carrier while the carrier itself remains intact and can be reused for subsequent fabrication processes, reducing waste and fabrication costs.
3Strength
If the bonding force between carrier and built-up structure is strong, then the structure is stable during fabrication, but the carrier cannot be easily removed
Solution Approach 1:
The bonding characteristics are differentiated in specific regions. The bonding force between the carrier and the built-up structure is designed to be greater than the bonding force between the carrier and the release layer, enabling selective separation. This local quality differentiation allows stable fabrication while facilitating easy carrier removal and reuse.
4Strength
If a conventional core board is used, then the packaging substrate has structural support, but the conductive path length and overall thickness increase
Solution Approach 1:
The invention extracts and eliminates the conventional core board from the packaging substrate structure. By using a carrier-based built-up structure without a core board, the conductive path length is shortened and the overall thickness is reduced, while maintaining structural support through the carrier and built-up design.
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 stress on the packaging substrate, preventing warpage and increasing yield, while allowing carrier reuse to lower costs and minimize waste.
Implementation Method 1
a pressure sensitive adhesive layer formed on at least one surface of the carrying board
Data Source
AI summary
A fabrication method of a coreless packaging substrate is provided, including the steps of: forming an inner built-up circuit board on a carrier; removing the carrier; and symmetrically forming a first outer built-up structure and a second outer built-up structure on top and bottom surfaces of the inner built-up circuit board, respectively. The present invention effectively increases the product yield, saves the fabrication cost, and reduces wastes.