Thermal Flow Meter Semiconductor Chip Molding Stress
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Solution Overview
Problem
Bending stress caused by molding can lead to deformation and breakage of semiconductor chips in thermal type flowmeters, particularly due to increased pressing force from tolerance issues between the chip and other components.
Innovation Solution
A method of manufacturing thermal type flowmeters that involves a two-step resin molding process, where the circuit package is first produced and then integrated with the housing, using a specific molding technique to distribute pressure evenly and prevent excessive bending stress on the semiconductor chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a mold presses the surface of the semiconductor chip during manufacturing, then the circuit package can be formed and integrated with the housing, but bending stress acts on the semiconductor chip causing deformation and breakage
Solution Approach 1:
The patent divides the molding process into two distinct stages: first molding the circuit package with the semiconductor chip, and then molding the housing that integrates with the circuit package. This segmentation allows the semiconductor chip to be protected during the first molding process, and the housing to be formed separately in the second process, eliminating the need for the mold to press directly on the chip during housing formation.
Solution Approach 2:
The circuit package is molded and formed in advance before the housing is molded. This preliminary action completes the circuit package structure with the semiconductor chip securely in place, so that subsequent housing molding does not require direct contact with or pressing on the chip, thereby preventing bending stress.
2Strength
If pressing force of the mold is increased to ensure proper integration, then the housing and circuit package can be securely bonded, but excessive bending stress causes breakage of the semiconductor chip
Solution Approach 1:
The patent separates the bonding process into two stages: first bonding the semiconductor chip to the circuit package substrate during circuit package molding, and then bonding the circuit package to the housing during housing molding. This segmentation ensures that high pressing forces are never applied to the chip itself, only to the already-bonded circuit package assembly.
Solution Approach 2:
The circuit package is formed as a protective structure beforehand that cushions and distributes any pressing forces during housing molding. The mold contacts only the housing material and the outer surfaces of the circuit package, not the semiconductor chip, thereby cushioning the chip from excessive stress.
3Manufacturing precision
If the semiconductor chip is held in place during molding, then proper positioning can be achieved, but the chip is susceptible to deformation from mold pressure
Solution Approach 1:
The patent segments the positioning and pressure application processes: the semiconductor chip is positioned and fixed to the circuit package substrate during the first molding process, and then the housing is molded around this assembled unit. This ensures precise chip positioning is achieved before any housing molding pressure is applied, and the chip is protected from subsequent pressure.
Solution Approach 2:
The circuit package substrate acts as an intermediary between the semiconductor chip and the mold during housing molding. The substrate receives and distributes any mold pressure, preventing direct transmission of harmful forces to the chip while maintaining the chip's precise position through its already-established bonding.
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 approach effectively reduces deformation and breakage of semiconductor chips, enhancing the precision and reliability of the thermal type flowmeter by maintaining high precision in the shapes and positional relationships of the accessory paths and heat transfer surfaces.
Implementation Method 1
a flow volume detection unit that is arranged in the accessory path and is configured to measure a state of measurement target gas flowing through the accessory path by heat transfer with the measurement target gas
Data Source
Figure 1
Figure 2(A)~2(B)
Figure 3(A)~3(B)
AI summary
In order to provide a method of manufacturing a thermal type flowmeter that is capable of reducing deformation of a semiconductor chip, which is caused by molding, the present invention provides a method of manufacturing a thermal type flowmeter 300 that includes a circuit package 400 of a resin-molded semiconductor chip 602, the method including: resin-molding the semiconductor chip 602 in a state in which a mold 703 is pressed against a heat transfer surface 437 that is provided on a surface of the semiconductor chip 602 and a pressed surface 602a that is set on the surface of the semiconductor chip 602 at a position separate from the heat transfer surface 437.