OCXO Ground Pattern Layout for Low-Profile Thermal Stability
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Solution Overview
Problem
Conventional oven controlled crystal oscillators face challenges in achieving temperature stability and low profile due to the use of heat tubes, which hinder efficient heat transfer and lead to displacement of the crystal unit during solder reflow.
Innovation Solution
The oven controlled crystal oscillator design eliminates the heat tube by using a metal pattern with high thermal conductivity to connect the crystal unit, thermistor, and power transistor, allowing direct soldering and ensuring the crystal unit is secured in a predetermined position through a slit or depressed portion on the circuit board, enhancing thermal responsiveness and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat tube is used to transfer heat from the heat source to the crystal unit, then the heat transfer path is extended and structural support is provided, but the profile height increases and thermal responsiveness is reduced
Solution Approach 1:
The patent removes the heat tube from the system entirely. Instead of using a separate heat tube component to transfer heat, the invention uses the circuit board's ground pattern as the heat transfer path, thereby eliminating the need for the heat tube and reducing profile height while maintaining temperature stability.
Solution Approach 2:
The patent combines the heat transfer function with the electrical ground connection function. The ground pattern on the circuit board serves dual purposes: providing electrical grounding and serving as a thermal conduction path from the heat source to the crystal unit, thereby eliminating the need for a separate heat tube.
2Reliability
If a heat tube is used to support the crystal unit, then structural support is provided, but the crystal unit may be displaced during solder reflow
Solution Approach 1:
The patent removes the heat tube's mechanical support function and replaces it with a dedicated positioning structure consisting of a positioning hole and positioning protrusion. This separation of functions allows the crystal unit to be precisely positioned and secured during solder reflow without relying on the heat tube.
Solution Approach 2:
The patent implements preliminary positioning of the crystal unit through the positioning hole and positioning protrusion before soldering. This preliminary action ensures the crystal unit is correctly positioned and secured, preventing displacement during the subsequent solder reflow process.
3Length of stationary object
If the crystal unit is directly soldered to the circuit board without a heat tube, then profile height is reduced, but thermal responsiveness and temperature stability deteriorate
Solution Approach 1:
The patent makes the ground pattern multi-functional by using it for both electrical grounding and thermal conduction. This allows direct soldering of the crystal unit to the circuit board (reducing profile height) while maintaining temperature stability through the ground pattern's thermal conduction path.
Solution Approach 2:
The ground pattern acts as an intermediary for heat transfer between the heat source and the crystal unit. Instead of direct contact or using a heat tube, the ground pattern mediates the thermal energy transfer, maintaining temperature stability while allowing for a lower profile design.
4Ease of manufacture
If the crystal unit is directly soldered to the circuit board without positioning structures, then manufacturing is simplified, but the crystal unit may be displaced during solder reflow
Solution Approach 1:
The patent implements preliminary positioning of the crystal unit through the positioning hole and positioning protrusion before soldering. This preliminary action ensures the crystal unit is correctly positioned and secured, preventing displacement during the subsequent solder reflow process while maintaining manufacturing simplicity.
Solution Approach 2:
The positioning structure is integrated into the circuit board itself, with the positioning hole formed directly in the board and the positioning protrusion provided by the crystal unit's casing. This self-service approach ensures proper positioning without requiring additional external fixtures or complex mounting procedures.
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 configuration improves temperature stability and reduces the oscillator's height, ensuring efficient heat transfer and maintaining the crystal unit's position during solder reflow, resulting in an oscillator with excellent temperature characteristics and a low profile.
Implementation Method 1
The metal pattern commonly connects a ground terminal of the crystal unit, a collector of the power transistor, and a ground terminal of the thermistor. The power transistor becomes a heat source.
Implementation Method 2
The power transistor becomes a heat source.
Data Source
AI summary
An oven controlled crystal oscillator includes a crystal unit, a temperature control circuit, and a circuit board. The temperature control circuit is configured to control a temperature of the crystal unit. The crystal unit includes a flange that projects outward to an entire outer periphery in one end. The circuit board includes a depressed portion in which the flange is partially inserted. The temperature control circuit includes a power transistor, a thermistor as a temperature sensor, and a metal pattern. The power transistor becomes a heat source. The metal pattern commonly connects a ground terminal of the crystal unit, a collector of the power transistor, and a ground terminal of the thermistor. The crystal unit is positioned in a state where the flange is partially inserted in the depressed portion. The crystal unit is connected to the metal pattern.