PCB Expansion Control in Integrated Sensor-Lens Assemblies
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Solution Overview
Problem
In image capture apparatuses, the expansion of printed circuit boards (PCBs) due to temperature and humidity fluctuations causes misalignment of lenses and image sensors, leading to issues such as focus shift and distortion.
Innovation Solution
The integration of a PCB with a coefficient of thermal expansion and hygroscopic expansion within specific ranges, combined with a laminated construction and increased number of vias, constrains the PCB's expansion along the optical axis, maintaining focus alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PCB is made from conventional materials without expansion constraints, then the manufacturing and assembly process is simple, but the PCB expands due to temperature and humidity fluctuations causing misalignment and focus shift
Solution Approach 1:
The patent applies parameter changes by carefully selecting PCB materials with specific coefficient of thermal expansion (CTE) and coefficient of hygroscopic expansion (CHE) values within defined ranges. This material parameter selection allows the PCB to expand minimally and predictably with environmental changes, maintaining focus alignment without requiring complex mechanical constraint structures.
Solution Approach 2:
The patent employs composite materials by using a multi-layer PCB construction where different material layers are combined to achieve desired expansion characteristics. The composite structure integrates materials with complementary properties to balance thermal and hygroscopic expansion, providing both structural integrity and dimensional stability.
2Manufacturing precision
If the PCB uses materials with low expansion coefficients, then focus alignment is maintained, but the selection of materials becomes more restricted and potentially more expensive
Solution Approach 1:
The patent defines specific parameter ranges for CTE (20-70 ppm/°C) and CHE (20-50 ppm/100% RH) that balance manufacturing precision requirements with material availability. These parameter specifications enable manufacturers to select from a practical range of standard materials while achieving sufficient alignment tolerance for the application.
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 inhibits PCB expansion, ensuring consistent focus alignment and improved image quality by maintaining the optical tolerance loop within acceptable manufacturing tolerances.
Implementation Method 1
a coefficient of thermal expansion that lies substantially within the range of approximately 20 ppm/° C. to approximately 70 ppm/° C.
Implementation Method 2
a coefficient of hygroscopic expansion that lies substantially within the range of approximately 20 ppm/100% RH absorption to approximately 50 ppm/100% RH absorption
Data Source
AI summary
An integrated sensor-lens assembly (ISLA) for an image capture apparatus that defines an optical axis and includes: a lens holder; a cover glass holder that is connected to the lens holder, a printed circuit board (PCB) that is (directly or indirectly) connected to the cover glass holder within an optical tolerance loop of the ISLA; and an image sensor that is supported by the PCB. The ISLA is configured such that expansion of the PCB along the optical axis is constrained so as to maintain focus alignment of the ISLA.