Upright PTC Over-Current Protection Device Preventing Solder Wicking
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Solution Overview
Problem
Traditional surface-mountable over-current protection devices for high-voltage applications face issues with solder wicking, leading to insufficient isolation and inferior voltage endurance due to their complex design and large size.
Innovation Solution
A surface-mountable over-current protection device with a laminated structure comprising a PTC material layer sandwiched between two conductive layers, featuring electrodes that form a perpendicular end surface for easy mounting on a circuit board, using PCB processes like solder masking, copper-plating, and tin-plating to enhance voltage endurance and prevent solder wicking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional SMD over-current protection device with compact circuit design is used for high voltage applications, then the device size is reduced, but solder wicking event occurs causing insufficient isolation and inferior voltage endurance
Solution Approach 1:
The patent transitions from a planar PCB-mounted design to a three-dimensional upright standing structure. The device stands vertically on the circuit board with electrodes forming an end surface perpendicular to the circuit board, creating spatial separation that prevents solder wicking while maintaining compact footprint. This dimensional change allows the device to achieve both small size and high voltage endurance by utilizing vertical space rather than horizontal expansion.
2Device complexity
If traditional SMD over-current protection device with compact circuit design is used, then manufacturing complexity is reduced, but solder wicking causes insufficient isolation
Solution Approach 1:
By standing upright on the circuit board with electrodes forming a perpendicular end surface, the device creates physical and electrical isolation from the circuit board plane. This vertical orientation prevents solder molten metal from wicking between electrodes during the soldering process, eliminating the solder wicking issue while maintaining simple manufacturing processes.
3Reliability
If over-current protection device is designed to withstand high voltage (60-600 volts), then voltage endurance is improved, but device size increases making it suitable only for upright mounting
Solution Approach 1:
The upright mounting configuration utilizes vertical space to achieve high voltage endurance without proportionally increasing horizontal footprint. The device stands vertically with electrodes arranged to maximize isolation in the vertical dimension, allowing high voltage applications while maintaining a compact area on the circuit board.
Solution Approach 2:
The device employs a laminated structure comprising multiple conductive layers and PTC material layers bonded together. This composite construction provides both mechanical strength for high voltage withstanding and compact dimensions, as the layered structure achieves electrical isolation and structural integrity in a space-efficient manner.
4Reliability
If PTC device resistance increases to high resistance state to suppress over-current, then over-current protection is achieved, but voltage drop occurs affecting circuit operation
Solution Approach 1:
The PTC material exhibits temperature-dependent resistance changes, remaining at extremely low resistance during normal operation to minimize voltage drop, and transitioning to high resistance state when heated by over-current to provide protection. This dynamic parameter change allows the device to adapt its electrical characteristics based on operating conditions.
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 device effectively withstands voltages from 60 to 600 volts, simplifies manufacturing processes, reduces costs, and prevents short circuits caused by solder wicking, ensuring reliable high-voltage endurance and stability.
Implementation Method 1
The resistance of a positive temperature coefficient (PTC) device is very sensitive to temperature variation. The resistance of the FTC device remains extremely low at normal temperature... when the PTC device heats up to a critical temperature due to an over-current or an over-temperature event occurring in the circuit or cell, the resistance instantaneously increases to a high resistance state
Implementation Method 2
The first conductive layer is in physical contact with the first planar surface of the PTC material layer, and the second conductive layer is in physical contact with the second planar surface of the PTC material layer. The first electrode is disposed on the first conductive layer. The second electrode is disposed on the second conductive layer
Data Source
AI summary
An over-current protection device, which can be surface-mounted and stand upright on a circuit board and withstand 60 to 600 volts, comprises a PTC device, first and second electrodes. The PTC device is a laminated structure comprising first and second conductive layers and a PTC material layer. The first and second conductive layers are in physical contact with first and second planar surfaces of the PTC material layer, respectively. The first electrode is disposed on the first conductive layer. The second electrode is disposed on the second conductive layer and is separated from the first electrode. The first electrode, the second electrode and the PTC device commonly form an end surface which is substantially perpendicular to the first and second planar surfaces. The first electrode and the second electrode at the end surface serve as interfaces electrically connecting to the circuit board.