Electroacoustic Component Reflow Assembly With Oxidation-Resistant Pads
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Solution Overview
Problem
Existing methods for assembling electroacoustic components to electronic circuits by reflow soldering face challenges in achieving reliable and efficient connections, particularly in ultrasonic devices.
Innovation Solution
A method involving the formation of connection pads with a stack of bonding, metal, and finishing layers, followed by the deposition of solder balls and subsequent melting to create robust bonds between electroacoustic and electronic circuits, using materials like chromium, copper, and gold, and employing a tungsten carbide coating to enhance bonding and prevent short-circuiting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a simple soldering process is used to assemble electroacoustic components to electronic circuits, then the manufacturing process is simple and fast, but the connection reliability and bonding strength are insufficient
Solution Approach 1:
The patent applies preliminary action by pre-forming a multi-layer pad structure (bonding layer, metal layer, finishing layer) on both the electroacoustic component and electronic circuit before the soldering process. The bonding layer (chromium) is prepared in advance to ensure strong adhesion, the metal layer (copper) is pre-deposited for electrical conductivity, and the finishing layer (gold) is applied beforehand to prevent oxidation. This preliminary preparation of the pad structure ensures reliable connections while maintaining a relatively simple overall manufacturing process.
2Reliability
If oxidation prevention measures are implemented on connection pads, then the bonding reliability is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent employs composite materials by creating a multi-layer pad structure consisting of different materials with specific functions: chromium bonding layer for adhesion, copper metal layer for electrical conductivity, and gold finishing layer for oxidation prevention. This composite structure integrates multiple functions (bonding, conduction, protection) into a single integrated pad system, improving bonding reliability without requiring separate complex manufacturing steps for each function.
3Reliability
If short-circuit prevention measures are implemented between connection pads, then the device reliability is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent applies the taking out principle by selectively removing portions of the tungsten carbide coating between the connection pads. The tungsten carbide coating is first applied over the entire surface to provide protection and prevent short-circuits, then the portions between the pads are removed through photolithography and etching processes. This creates isolation grooves that prevent short-circuits between adjacent pads while maintaining the protective function where needed, improving device reliability without adding significant manufacturing complexity.
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 ensures strong, reliable connections between electroacoustic and electronic components, enhancing the performance and durability of ultrasonic devices by minimizing oxidation and short-circuit risks.
Implementation Method 1
melting the solder balls so that they adhere to the first connection pads
Implementation Method 2
melting the solder balls so that they adhere to the first connection pads; melting again the solder balls so that they adhere to the first connection pads and to the second connection pads
Implementation Method 3
each first connection pad comprises a stack of a bonding layer, of a metal layer, and of a finishing layer, the metal layer being interposed between the bonding layer and the finishing layer, the bonding layer being in direct physical contact with the electroacoustic component and with the metal layer
Implementation Method 4
the metal layer is made of copper
Implementation Method 5
the finishing layer is made of gold
Data Source
AI summary
The present description concerns a method of manufacturing an ultrasonic device comprising an electronic circuit and an electroacoustic component, the method comprising the forming of first connection pads bonded to a plate comprising one electroacoustic component or a plurality thereof, the forming of solder balls on the first pads, the melting of the solder balls so that they adhere to the first pads, optionally the cutting of the plate to separate the electroacoustic components, the forming of second connection pads bonded to the electronic circuit, the application of the electroacoustic component to the electronic circuit so that the solder balls come into contact with the second pads, and the melting of the solder balls so that they adhere to the first pads and to the second pads.