Photopolymerization Layer Patterning via Two-Stage UV Exposure
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Solution Overview
Problem
Conventional photopolymerization layer patterning in printed circuit boards faces issues due to mask contamination and compression, leading to yield reduction, especially with thick or colored layers, as well as limitations in using high-energy UV sources with digital micro-lens devices.
Innovation Solution
A two-stage exposure process using a low-power UV source and a high-power mercury lamp, where the UV source initiates curing from the top and the mercury lamp completes curing from the bottom, with a mask used in the second stage to prevent particle contamination and ensure thorough curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If masks are used for exposure, then patterning can be achieved, but mask contamination with particles causes pores and compressive damage to the photopolymerization layer
Solution Approach 1:
The photopolymerization layer is pre-cured with a low-power UV source before mask exposure. This preliminary curing creates a protective hardened surface that prevents particle contamination and compressive damage during subsequent mask exposure, while still allowing the mask to pattern the uncured deeper regions
Solution Approach 2:
The low-power UV pre-exposure acts as a cushioning protective layer that absorbs the harmful effects of mask particles and compression, preventing them from reaching and damaging the uncured photopolymerization material beneath
2Use of energy by moving object
If high-power UV source is used with digital micro-lens device, then sufficient energy for complete curing can be provided, but the digital micro-lens device cannot tolerate overly high energy due to heat dissipation limits
Solution Approach 1:
The exposure process is segmented into two distinct stages: first a low-power UV source performs digital micro-lens patterning for precise top-layer curing, then a high-power mercury lamp provides the additional energy needed for complete through-curing of thick layers, dividing the energy delivery function between two specialized sources
Solution Approach 2:
The low-power UV pre-exposure acts as an intermediary that prepares the photopolymerization layer by curing the top portion, which then enables the subsequent high-power mercury lamp exposure to complete the curing process without overwhelming the digital micro-lens device
3Reliability
If low-power UV source is used to protect digital micro-lens device, then the device can operate within tolerance, but low-power UV cannot reach the bottom of thick photopolymerization layers to cure them sufficiently
Solution Approach 1:
The curing process is segmented vertically: the low-power UV source cures the top portion of the photopolymerization layer where precise patterning is needed, while the high-power mercury lamp cures the deeper, thicker portions that require more energy, with each source optimized for its specific depth range
Solution Approach 2:
The exposure parameters are changed between two stages: first using low-power UV with digital micro-lens for precise top-layer patterning, then switching to high-power mercury lamp for deep through-curing, changing both the energy level and the exposure mechanism to match the different depth requirements
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 process enhances patterning yield by preventing particle-induced pores and compressive damage, effectively curing thick layers and offering a cost-effective alternative to maskless lithography.
Implementation Method 1
performing first-instance exposure on the photopolymerization layer, using a UV source and a digital micro-lens device, wherein the energy provided by the UV source during the first-instance exposure is less than the exposure energy required for complete curing of the photopolymerization layer
Implementation Method 2
performing second-instance exposure on the photopolymerization layer, using a mercury lamp and the mask, wherein energy provided by the mercury lamp during the second-instance exposure is no less than the difference between the exposure energy required for the complete curing of the photopolymerization layer and the energy provided during the first-instance exposure
Data Source
AI summary
A method for exposing a photopolymerization layer comprising photopolymers includes: providing a printed circuit board, with a photopolymerization layer disposed on the top side of the printed circuit board; performing first-instance exposure on the photopolymerization layer, using a UV source and a digital micro-lens device, wherein the UV source is of a power less than 0.2 kW; stopping the first-instance exposure; covering the photopolymerization layer with a mask, with the mask having a bottom side in contact with the photopolymerization layer; and performing second-instance exposure on the photopolymerization layer, using a mercury lamp and the mask, wherein the mercury lamp is of a power greater than 5 kW.