Piezoelectric Transformer PCB Conductive Resistor Pyroelectric Voltage
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Solution Overview
Problem
In the flow soldering process, piezoelectric transformers generate high pyroelectric voltages due to the pyroelectric effect, which can cause electrostatic discharge damage to semiconductor components, as the existing methods either require reliable and costly conductive jigs or fail to adequately suppress voltage during abrupt temperature rises.
Innovation Solution
A printed circuit board with a conductive resistor coupling the primary side electrodes of the piezoelectric element, which reduces pyroelectric voltage by managing the resistance value and temperature rise rate, preventing electrostatic discharge damage to semiconductor components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conductive jig is used to short-circuit the primary side terminals of a piezoelectric transformer, then the pyroelectric voltage is suppressed, but the device complexity and cost increase due to the need for reliable mounting of the jig
Solution Approach 1:
The harmful function of generating high pyroelectric voltage is extracted and neutralized by introducing a resistive element that provides an alternative discharge path for the pyroelectric current, preventing voltage buildup without requiring external jigs or complex modifications to the piezoelectric transformer itself
Solution Approach 2:
A resistive element is introduced as an intermediary component between the primary side terminals of the piezoelectric transformer, serving as a mediator that safely dissipates pyroelectric current through resistance, thereby protecting semiconductor components without requiring direct short-circuiting mechanisms
2Object-affected harmful factors
If a resistive element is soldered to the primary side terminals, then the pyroelectric voltage is suppressed, but the protection is insufficient during preheating and abrupt temperature rises before soldering
Solution Approach 1:
A conductive coating is applied to the primary side terminals during the manufacturing process, establishing the protective resistive path before the piezoelectric transformer is subjected to temperature changes during preheating or flow soldering, ensuring protection is in place from the outset
Solution Approach 2:
The resistance value of the protective layer is controlled by adjusting the thickness and conductivity of the conductive coating applied to the primary side terminals, allowing optimization of the discharge path characteristics to safely limit pyroelectric voltage under various temperature conditions
3Productivity
If the temperature rise rate is increased to improve productivity, then the flow soldering process is faster, but the pyroelectric voltage exceeds the electrostatic breakdown voltage of semiconductor components
Solution Approach 1:
The pyroelectric effect, which generates harmful high voltage during rapid heating, is converted into a beneficial protective mechanism by providing a controlled discharge path through the conductive coating, allowing rapid temperature increases for high productivity while preventing damage to semiconductor components
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 solution effectively reduces pyroelectric voltage, protecting semiconductor components from electrostatic discharge while maintaining circuit efficiency and cost-effectiveness by using a conductive coating resistor and optimizing board slit dimensions.
Implementation Method 1
a piezoelectric transformer is heated to as high as several hundred degrees, and a high voltage is generated at the terminal owing to the pyroelectric effect
Implementation Method 2
a conductive resistor that couples two electrodes arranged on a primary side of the piezoelectric element
Implementation Method 3
dipping the board into a flow solder bath containing molten solder. More specifically, soldering is performed by forming a jet flow of molten solder (solder jet flow)
Data Source
AI summary
A piezoelectric transformer includes a piezoelectric element. Two primary side electrodes exist on the primary side of the piezoelectric element. The primary side electrodes are coupled by a resistor formed from a conductive coating. A discharge current is discharged via the resistor to protect a semiconductor component from the discharge current. Since neither a short-circuit terminal nor conductive jig is required, electrostatic discharge damage to a semiconductor component can be prevented by a low-cost arrangement.