SAW Filter Resin Substrate Thermal Stress Management
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Solution Overview
Problem
Existing circuit modules with surface acoustic wave filters, including piezoelectric elements, face damage risks during heating or cooling due to material property mismatches between the piezoelectric substrate, ceramic base, and glass epoxy resin mother substrate, leading to differential deformations and potential connection damage.
Innovation Solution
A circuit module design featuring a surface acoustic wave filter mounted on a resin substrate, which is then mounted on a multilayer substrate and a mother substrate, using materials with matched coefficients of linear expansion and Young's moduli to minimize deformation and connection damage during thermal processes, and employing solder bumps for connection, which are less prone to damage than gold bumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a piezoelectric single crystal substrate is mounted directly on a ceramic base substance, then the device structure is simple, but connection damage occurs during heating or cooling due to material property mismatches
Solution Approach 1:
A resin substrate is introduced as an intermediary layer between the piezoelectric single crystal substrate and the ceramic base substance. This resin substrate acts as a stress-absorbing buffer that compensates for the differential thermal expansion and deformation between the piezoelectric substrate and ceramic base during heating or cooling processes, thereby preventing connection damage while maintaining structural integrity.
Solution Approach 2:
The invention uses a composite structure combining piezoelectric single crystal substrate, resin substrate, and ceramic base substance. Each material is selected for its specific properties: the piezoelectric substrate provides functional performance, the resin substrate provides stress buffering with matched thermal expansion characteristics, and the ceramic base provides mechanical support. This composite approach resolves the contradiction by combining materials with complementary properties.
2Adaptability or versatility
If materials with different coefficients of linear expansion are used, then manufacturing flexibility is high, but differential deformation occurs during thermal processes
Solution Approach 1:
The invention carefully selects and controls the thermal expansion parameters of the resin substrate to match those of the piezoelectric single crystal substrate. By adjusting the resin material composition and curing conditions, the coefficient of linear expansion of the resin substrate is optimized to be equal to or close to that of the piezoelectric substrate, thereby minimizing differential deformation during thermal processes while maintaining manufacturing flexibility.
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 suppresses or prevents connection damage within the circuit module during heating or cooling by using a resin substrate with a low Young's modulus to absorb and distribute stress, and solder bumps to reduce the risk of deformation, thereby enhancing the module's thermal stability and reliability.
Implementation Method 1
using a resin substrate with a low Young's modulus to absorb and distribute stress
Implementation Method 2
surface acoustic wave filters including piezoelectric elements
Data Source
AI summary
A circuit module and a composite circuit module, which suppress or prevent damage to a connection to or within a device when heat is applied, includes a SAW filter including a piezoelectric substrate. In a package substrate that is a resin substrate, the SAW filter is mounted. A mounting substrate is a multilayer substrate mounted on a mother substrate, and the package substrate is mounted therein.