Serpentine Heating Element for Thermal Pattern Sensor Routing
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Solution Overview
Problem
The challenge in manufacturing thermal pattern sensors, such as fingerprint sensors, lies in the complex and costly process of routing signals from a matrix of pixels to an integrated circuit, requiring precise alignment and small vias, which increases manufacturing costs and decreases production yield due to the need for fine routing lines and precise alignment.
Innovation Solution
A thermal pattern sensor design featuring a serpentine-shaped heating element with connection sections that allows for easier routing and relaxed alignment constraints, enabling larger vias and less expensive substrates, with the integrated circuit controlling the heating elements by applying potentials to sections of the serpentine path to heat rows of pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional routing lines and small vias are used to connect the pixel matrix to the integrated circuit, then signal connection is achieved, but manufacturing precision requirements increase and production yield decreases
Solution Approach 1:
The heating lines are configured in a serpentine pattern that extends in both horizontal and vertical directions, utilizing two-dimensional space on the substrate. This allows connection points to be distributed across multiple locations rather than requiring precise alignment at a single point, effectively transforming a one-dimensional alignment problem into a two-dimensional connection network that is more tolerant of manufacturing variations
Solution Approach 2:
The heating lines are divided into multiple segments connected in series, forming a serpentine path. Each segment can be independently routed to nearby connection points, and the segmented structure provides multiple potential connection locations. This segmentation reduces the precision required for each individual connection while maintaining overall signal integrity across the entire heating line network
2Area of stationary object
If small vias and fine routing lines are used, then space is saved on the substrate, but manufacturing cost increases and production yield decreases
Solution Approach 1:
The serpentine configuration allows heating lines to utilize vertical space in addition to horizontal space, effectively packing more functionality into the available substrate area without requiring excessively narrow line widths. The pattern winds back and forth, maximizing area utilization while maintaining reasonable via and line dimensions that are easier and less costly to manufacture
Solution Approach 2:
The heating lines are merged into a continuous serpentine path that serves multiple functions: heating multiple rows of pixels sequentially, providing multiple connection points for routing, and utilizing substrate space efficiently. This merged structure eliminates the need for separate heating elements for each row, reducing overall complexity and manufacturing cost while improving space utilization
3Manufacturing precision
If precise alignment is required for vias and routing lines, then connection accuracy is improved, but production yield decreases
Solution Approach 1:
The heating lines are segmented into multiple sections with connection points at regular intervals. This segmentation provides redundancy in the connection system, meaning that if one via or connection point is misaligned or defective, alternative connection points are available. This reduces the impact of alignment errors on overall production yield while maintaining acceptable connection accuracy
Solution Approach 2:
The serpentine heating line structure acts as an intermediary between the integrated circuit and the pixel matrix. Instead of requiring direct, precise alignment between fine routing lines and small vias, the serpentine pattern provides a more robust intermediate connection structure with larger, more tolerant connection points that mediate the connection process and reduce sensitivity to alignment variations
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 simplifies the connection of the matrix to the integrated circuit, reduces manufacturing costs, and increases production yield by allowing larger vias and less stringent alignment requirements, facilitating the use of less expensive substrates and easier testing of line continuity.
Implementation Method 1
Each pixel comprises a pyroelectric capacitor formed by two conductive electrodes between which a portion of pyroelectric material is arranged, and a heating element. This heating element dissipates a certain quantity of heat in the pixel and the heating of the pixel is measured after a certain acquisition time
Implementation Method 2
Each pixel comprises a pyroelectric capacitor formed by two conductive electrodes between which a portion of pyroelectric material is arranged... thermal detection means may correspond to pyroelectric elements... making it possible to convert a variation in temperature into a variation in potential or electric current
Data Source
Figure 1~2
Figure 3
Figure 3'
AI summary
The invention relates to a pixel matrix of a thermal pattern sensor comprising several rows and several columns of pixels, said matrix comprising: - an active thermal element formed by a thermosensitive material disposed between a lower layer and an upper layer, the lower layer being made up of a plurality of first tracks in electrically conductive material and extending in a first direction, said first tracks forming columns of pixels;- a heating element, disposed on the active thermal element and forming a serpentine pattern, said heating element being made up of a plurality of second tracks (L1, L2, L3, L4, L5, L6) of electrically conductive material and connecting sections (w1, w2, w3, w4, w5, w6) of electrically conductive material connected to the ends of the second tracks (L1, L2, L3, L4, L5, L6), said second tracks (L1, L2, L3, L4, L5, L6) extending in a second direction different from the first direction and forming pixel lines, the second tracks being connected, with the exception of the first and last second tracks (L1, L2, L3, L4, L5, L6), by their respective ends to one end of a preceding second track and a following second track via said sections (w1, w2, w3, w4, w5, w6) w6) connection, the first and last second tracks having a free end connected to a connecting segment.;