LED Head Substrate Warpage Control via Wiring Ratio
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Solution Overview
Problem
The substrate in light exposure devices used in image forming apparatuses tends to warp due to temperature increases from light emission, leading to shifts in light irradiation position and decreased printing quality, especially when the metal wiring pattern structure is asymmetric.
Innovation Solution
The substrate is divided into two regions with specific ratios of metal wiring pattern areas to prevent warpage by ensuring the occupancy ratio of metal wiring patterns in each region maintains a balanced distribution, thereby reducing thermal expansion-induced warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the substrate temperature increases due to light emission, then the light emitting element can function properly, but the substrate warps and the light irradiation position shifts
Solution Approach 1:
The patent applies local quality by creating non-uniform metal wiring pattern distributions in different regions of the substrate. Specifically, the first region has a different metal wiring pattern area ratio compared to the second region, allowing each region to compensate for thermal expansion differently. This localized variation in wiring pattern density creates differential thermal expansion that counteracts the warping tendency, maintaining flatness while allowing the substrate to reach operational temperatures.
Solution Approach 2:
The patent directly utilizes thermal expansion principles by designing metal wiring patterns with specific area ratios in different regions. The metal wiring patterns serve as thermal expansion compensation structures - when the substrate heats up during light emission, the differential thermal expansion between regions with different metal wiring densities creates internal stresses that prevent warping. This allows the substrate to maintain flatness despite temperature increases up to operational levels.
2Reliability
If the metal wiring pattern structure is asymmetric, then electrical connection is achieved, but the substrate warps in the sub-scanning direction
Solution Approach 1:
The patent applies asymmetry principle by intentionally designing asymmetric metal wiring pattern distributions across the substrate regions. The first and second regions have different metal wiring pattern area ratios, creating an asymmetric thermal expansion profile. This controlled asymmetry compensates for the asymmetric warping tendency caused by asymmetric electrical wiring requirements, maintaining both electrical connectivity and substrate flatness.
Solution Approach 2:
The patent uses local quality by varying the metal wiring pattern characteristics in different spatial regions of the substrate. Each region (first and second regions) has locally optimized wiring pattern density to compensate for regional warping tendencies. This localized optimization allows the substrate to maintain overall flatness while accommodating asymmetric electrical connection requirements in specific areas.
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 solution effectively minimizes substrate warpage and maintains consistent light irradiation, enhancing the printing quality by stabilizing the light exposure device even under temperature changes.
Implementation Method 1
The temperature of the substrate is increased by the light emission of the light emitting element in the above light exposure device, and the base material of the substrate and the metal wiring pattern formed on the base material expands in some cases.
Data Source
AI summary
An LED head includes a base material having one or more wiring pattern formation surfaces and one or more metal wiring patterns formed on the one or more wiring pattern formation surfaces. When the occupancy ratio of the one or more metal wiring patterns in a first region of a substrate is A, and the occupancy ratio of the one or more metal wiring patterns in a second region of the substrate is B, the LED head satisfies 0.75≤A/B≤1 or 0.75≤B/A≤1.