Sintered Cold Cathode Electrode Density Gradient
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Solution Overview
Problem
The existing sintered electrodes for cold cathode tubes face challenges such as high cathode drop voltage, mercury consumption, and reduced service life due to sputtering, and the cost and yield issues associated with drawing plate materials for closed-end cylindrical electrodes.
Innovation Solution
A sintered electrode with a cylindrical form having a bottom part and an opening part, where a lead-in wire is integrally joined with a higher density than the electrode, made from high-melting point metals like tungsten, molybdenum, or niobium, and sinter bonded, with a surface roughness of not more than 100 μm, to achieve strong bonding and reduced production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If nickel electrode is used in cold cathode tube, then the electrode material is easy to manufacture, but the cathode drop voltage is high and sputtering occurs reducing service life
Solution Approach 1:
The patent changes the material parameter from nickel to molybdenum, which has different physical and chemical properties including lower cathode drop voltage and higher resistance to sputtering, thereby improving service life while maintaining manufacturability
Solution Approach 2:
The patent uses a composite structure combining molybdenum sintered body with KOV foil and lead-in wire, where each material performs its optimal function: molybdenum for electron emission and sputtering resistance, KOV for sealing and electrical connection, creating a reliable electrode assembly
2Reliability
If closed-end cylindrical electrode is formed by drawing plate material, then the cathode drop voltage is reduced and sputtering is suppressed, but the manufacturing cost increases and yield decreases
Solution Approach 1:
The patent replaces the expensive drawn plate material with a sintered body made from metal powder, which is a more cost-effective and higher yield process, while still achieving the closed-end cylindrical shape needed for holocathode effect
Solution Approach 2:
The patent changes the manufacturing process parameter from drawing (mechanical forming) to sintering (thermal consolidation of powder), which reduces manufacturing cost and improves yield while producing the required closed-end cylindrical electrode structure
3Reliability
If KOV foil welding is used to join lead-in wire to electrode, then the connection is reliable, but the manufacturing process becomes complex and costly
Solution Approach 1:
The patent merges the lead-in wire and electrode into a single sintered body, eliminating the need for separate welding steps with KOV foil, thereby simplifying the manufacturing process while maintaining reliable electrical connection and structural integrity
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 results in a cold cathode tube with low operating voltage, reduced mercury consumption, and extended service life, along with improved bonding strength and cost-effectiveness, eliminating the need for KOV foil welding.
Implementation Method 1
the adoption, as the electrode material, of Mo (molybdenum), Nb (niobium) or the like, which can lower the cathode drop voltage by about 20 V
Implementation Method 2
the service life of the lamp is likely to be lowered due to the occurrence of a phenomenon of the so-called sputtering. The sputtering phenomenon is that, during lighting of the cold cathode tube, ions collide with the electrode, and the electrode material scatters
Implementation Method 3
a lead-in wire is integrally joined to the bottom part and a requirement of d2/d1>1 is satisfied wherein d1 represents the density of the sintered electrode; and d2 represents the density of the lead-in wire
Data Source
AI summary
This invention provides a sintered electrode for a cold cathode tube in a cylindrical form having a bottom part on one end and an opening part on the other end, characterized in that a lead-in wire is joined integrally to the bottom part and a requirement of d2/d1>1 is satisfied wherein d1 represents the density of the sintered electrode; and d2 represents the density of the lead-in wire. According to the sintered electrode for a cold cathode tube, the bonding strength between the sintered electrode and the lead-in wire is high, and the handleability is good. The main component of the sintered electrode is particularly preferably identical to the main component of the lead-in wire. Enhancing the density of the lead-in wire can contribute to a further improvement, for example, in reliability.