OCXO Package Layout for Internal Temperature Stability
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Solution Overview
Problem
Downsizing Oven Controlled Crystal Oscillators (OCXO) while maintaining temperature control is challenging due to the high heat conductivity of ceramic packages, which leads to heat emission outside the package, making it difficult to control the temperature inside.
Innovation Solution
A crystal oscillator design where the substrate supports only the end portion of the crystal unit, circuit components, and heating element, with direct wire connections between the heating element and package terminals, avoiding substrate involvement, thus reducing heat transfer to the package and allowing for better temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a ceramic base with high heat conductivity is used for the package, then the mechanical strength and thermal management are improved, but the heat from the heating element is transmitted to the package and emitted outside, making temperature control difficult
Solution Approach 1:
The substrate is divided into a first surface and a second surface, with the heating element disposed on the first surface and the crystal unit on the second surface. This segmentation allows the substrate to act as a thermal barrier, preventing heat from the heating element from being transmitted to the package walls and emitted outside, thereby improving temperature control inside the package.
Solution Approach 2:
The substrate serves as an intermediary between the heating element and the package environment. By disposing the heating element on the first surface of the substrate and the crystal unit on the second surface, the substrate mediates thermal isolation, preventing direct heat transmission to the package walls while still allowing electrical connection through terminals.
2Device complexity
If the substrate is used to connect the heating element terminals to package terminals, then the electrical connection is simplified, but the substrate size increases and heat transfer to the package is enhanced
Solution Approach 1:
The connection structure transitions from a planar substrate-based connection to a three-dimensional wire-based connection. Wires extend from the first surface of the substrate to connect the heating element terminals to package terminals, utilizing the vertical dimension to reduce substrate area requirements while maintaining electrical connectivity.
Solution Approach 2:
The heating element connection function is extracted from the substrate and implemented separately using wires. This extraction allows the substrate to focus on its primary functions of mechanical support and thermal isolation, while the wire connections handle the electrical connectivity, thereby reducing the required substrate size.
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 enables the downsizing of OCXO while maintaining stable oscillation output and improving temperature controllability inside the package, as demonstrated by reduced temperature deviations during ambient temperature changes.
Implementation Method 1
a heating element regulating a temperature inside the package
Implementation Method 2
a wire that connects between a terminal disposed at the heating element and a terminal disposed inside the package without via the substrate
Data Source
AI summary
A crystal oscillator internally includes a package storing a crystal unit. The crystal oscillator is configured to include: a substrate having one surface side on which the crystal unit is disposed and another surface side on which a circuit component and a heating element are disposed, the circuit component including an oscillator circuit that oscillates the crystal unit, and the heating element regulating a temperature inside the package; a stepped portion formed at an inner wall of the package to support only an end portion of the substrate from the one surface side such that the crystal unit, the circuit component, and the heating element are spaced from a wall portion of the package; and a wire that connects between a terminal disposed at the heating element and a terminal disposed inside the package without via the substrate.