Transfer Mold Sensor Neutral Surface Warpage Control
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Solution Overview
Problem
Existing sensor devices face challenges in miniaturization and reliability due to warpage deformation caused by thermal changes, which affect the accuracy of acceleration and angular velocity measurements, especially when multiple sensors with different linear expansion coefficients are sealed with resin in a transfer mold package.
Innovation Solution
A transfer mold type sensor device is designed with a combined sensor thicker than the substrate and chip pad, where the combined sensor is arranged on a neutral surface in the package's cross-section, and the volumes of mold resin on and below this surface are equalized to minimize warpage deformation and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple sensors with different linear expansion coefficients are sealed with resin in a transfer mold package, then multi-functionality and mass productivity are improved, but warpage deformation occurs due to thermal expansion differences
Solution Approach 1:
The patent applies parameter changes by carefully selecting and adjusting the resin material's linear expansion coefficient to match a specific relationship with the sensors and substrate. The resin is designed to satisfy the inequality: αsensor < αresin < (αsubstrate × tsubstrate + αsensor × tsensor) / (tsubstrate + tsensor), where α represents linear expansion coefficients and t represents thicknesses. This parameter optimization resolves the technical contradiction by enabling multi-sensor integration while minimizing warpage deformation through thermal expansion compatibility.
2Volume of moving object
If sensors are miniaturized using fine processing technology of silicon, then device size is reduced and mass productivity is improved, but detection precision may be affected by deformation and inclination
Solution Approach 1:
The patent uses parameter changes by optimizing the resin's linear expansion coefficient to match the thermal expansion characteristics of the miniaturized silicon sensors and substrate. This ensures that during temperature changes, the resin expands and contracts at rates that prevent differential stress accumulation, thereby preventing sensor deformation and inclination that would compromise detection precision of the miniaturized device.
Solution Approach 2:
The patent employs transfer mold packaging, which is a cost-effective and efficient sealing method that enables mass productivity. The transfer mold process allows rapid encapsulation of multiple sensors in a standardized package, making the sensor device economical for widespread application while maintaining detection precision through proper resin selection.
3Volume of moving object
If package size is reduced for mounting in limited space, then ease of installation is improved, but stress concentration and deformation risk increase
Solution Approach 1:
The patent resolves the contradiction between miniaturization and stress reduction by optimizing the resin's linear expansion coefficient to match the thermal expansion characteristics of the compact package components. This parameter matching ensures that even in a reduced-size package, temperature-induced expansion and contraction occur uniformly, preventing stress concentration that would otherwise arise from differential expansion in compact geometries.
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 enhances the reliability and miniaturization of the sensor device by reducing deformation and stress, improving the stability of physical amount detection and reducing detection errors.
Implementation Method 1
linear expansion coefficients of embedded members such as the sensors and a substrate configuring the package and the sealing resin are different from each other
Data Source
AI summary
To provide a high-reliable transfer mold type sensor device in which a combined sensor including a plurality of sensors having a function of detecting physical amounts, a substrate processing a signal from the combined sensor and controlling a signal input/output with an external device, a chip pad mounted with the combined sensor and the substrate, and a lead frame are sealed with a mold resin and a package is formed, the combined sensor is configured to be thicker than the substrate and the chip pad, a principal surface side of the combined sensor is covered with the mold resin and a back surface side thereof contacts the substrate by a joint material, and the combined sensor is arranged on a package neutral surface in a cross-section of a thickness direction of the package including the combined sensor, the substrate, and the chip pad.