Wiring Substrate Warpage Control via Opposing Thermal Expansion
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Solution Overview
Problem
Coreless wiring substrates used in semiconductor packages are prone to warpage during temperature changes, leading to alignment issues and potential damage to wiring layers, and using a thick carrier to mitigate this increases costs and can cause deformation during peeling.
Innovation Solution
A wiring substrate design with a carrier bonded to one surface via an adhesive, featuring layers with different coefficients of thermal expansion, where the wiring member's pitch of wires is narrower on one surface than the other, causing opposite warping directions between the wiring member and the carrier, thereby canceling out warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a coreless substrate is used to reduce thickness, then the thickness of the wiring substrate is reduced, but the substrate becomes prone to warpage and is difficult to handle
Solution Approach 1:
A carrier is introduced as an intermediary component to support the coreless substrate during handling and mounting processes. The carrier provides mechanical support and ease of handling, while being removable after the substrate is secured, thus solving the handling difficulty without compromising the thin profile of the coreless substrate
2Ease of operation
If a coreless substrate is bonded to a stiff carrier to improve handling, then handling ease is improved, but warpage occurs during heating that reduces alignment accuracy
Solution Approach 1:
The carrier is designed with non-uniform thickness, being thicker at the edges and thinner at the center. This local variation in thickness creates differential thermal expansion characteristics that counteract the warpage tendency of the coreless substrate during heating, thereby maintaining alignment accuracy while preserving handling ease
3Stability of the object's composition
If a thick carrier is used to suppress warpage, then warpage is reduced, but costs increase and deformation occurs during peeling
Solution Approach 1:
The carrier employs a non-uniform thickness design with thicker edges and thinner center, achieving effective warpage suppression through strategic material distribution rather than uniform thickness. This reduces overall material consumption and cost, while the localized thickness variation prevents excessive stress concentration that would cause deformation during peeling
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 design significantly suppresses warpage of the wiring substrate, ensuring precise semiconductor chip alignment and reducing conveyance and appearance failures, while maintaining cost-effectiveness by avoiding excessive carrier thickness.
Implementation Method 1
a carrier that is bonded to the first surface via an adhesive and that includes a plurality of layers whose coefficients of thermal expansion are different from each other. When being heated, a direction in which the wiring member tends to warp and a direction in which the carrier tends to warp are opposite.
Data Source
AI summary
A wiring substrate includes: a wiring member that includes a first surface and a second surface, the wiring member including a plurality of wiring layers between the first surface and the second surface; and a carrier that is bonded to the first surface via an adhesive and that includes a plurality of layers whose coefficients of thermal expansion are different from each other. A pitch of wires included in the plurality of wiring layers is narrower on the second surface side than on the first surface side. When being heated, a direction in which the wiring member tends to warp and a direction in which the carrier tends to warp are opposite.