Temporary Fixation Substrate Edge Thinning for Reliable Laser Peeling
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Solution Overview
Problem
Existing FOWLP technologies face challenges in ensuring reliable peeling of temporary fixation substrates without residual resin or adhesive left on the substrate, particularly when using light-based peeling methods like laser lift-off, which affects the efficiency and yield of the semiconductor packages.
Innovation Solution
The temporary fixation substrate includes a thin region at the circumference of the substrate, with a thickness-reduced portion that facilitates efficient peeling by light irradiation, ensuring minimal residual resin or adhesive remains on the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the temporary fixation substrate has uniform thickness, then the structural strength is maintained, but the peeling reliability by light irradiation is reduced
Solution Approach 1:
The substrate transitions from uniform thickness to non-uniform thickness by creating a thin region at the circumference. This local thickness variation enables selective light transmission - the thin circumferential region allows light to pass through and ablate adhesive for reliable peeling, while the thick central region maintains structural strength and supports the semiconductor chip during processing.
2Productivity
If light irradiation is used for peeling, then the peeling speed is increased, but residual resin or adhesive remains on the substrate
Solution Approach 1:
The thin circumferential region is specifically designed to be transparent to laser light, allowing the laser to pass through and ablate the adhesive layer at the peeling interface. This localized optical property ensures complete adhesive removal at the circumference where peeling occurs, preventing residual adhesive while maintaining fast peeling speed.
Solution Approach 2:
The thin circumferential region acts as an intermediary that facilitates laser energy transmission to the adhesive layer. By creating this intermediate structure with optimized thickness, the laser energy can effectively reach and ablate the adhesive without being blocked by the substrate, enabling complete peeling without residue.
3Productivity
If the thin region width is increased, then the peeling efficiency is improved, but the structural stability of the substrate is reduced
Solution Approach 1:
The substrate is designed with a thin region of specific width (0.5mm to 2.0mm) at the circumference while maintaining adequate thickness in the central region. This creates distinct functional zones: the thin circumferential zone optimizes light transmission for efficient peeling, while the thick central zone provides structural stability to support the semiconductor chip during handling and processing.
Solution Approach 2:
The solution addresses the trade-off by utilizing the radial dimension of the substrate. Instead of uniformly reducing thickness, the thickness is varied in the radial direction - thin at the circumference and thick at the center. This dimensional variation allows simultaneous optimization of peeling efficiency (at the thin edge) and structural stability (at the thick center).
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
The thickness-reduced portion enhances the peeling efficiency and reliability of the temporary fixation substrate, reducing failures and improving the manufacturing yield of semiconductor packages.
Implementation Method 1
reliability of peeling of the temporary fixation substrate increases with increasing transmission of light, such as a laser, at a circumference
Implementation Method 2
A scheme of performing peeling by irradiation with light from the laser light source is so-called laser lift-off. That is to say, interfaces (adhered surfaces with an adhesive) between the temporary fixation substrate and semiconductor chips and a resin as objects to be fixed are irradiated with light, such as a laser, from a side of the temporary fixation substrate to ablate the adhesive to thereby peel the temporary fixation substrate
Data Source
AI summary
A temporary fixation substrate, peeled from a predetermined object to be fixed after once the predetermined object to be fixed is temporarily fixed to one main surface thereof, includes: a thin region being an annular region having a predetermined width from a lateral end; and a first thickness-reduced portion having been recessed from the one main surface on a side of the one main surface in the thin region, wherein a thickness in the thin region is smaller than a thickness in a region other than the thin region, and a difference between a thickness at the lateral end and the thickness in the region other than the thin region is 1 μm to 5 μm.