Solderless Stack Bonding for Phased Array Ultrasonic Transducers
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Solution Overview
Problem
Existing phased array ultrasonic testing (PAUT) transducer assembly methods are time-consuming and labor-intensive due to soldering, and they pose challenges with lead contamination, necessitating a lead-free, solderless assembly process for compliance with Restriction of Hazardous Substance (ROHS) regulations.
Innovation Solution
A solderless stack bonding method using a frame and pressure to align and permanently bond the pins of the flexible circuit with the conductive elements on the piezoelectric ceramic, employing epoxy as an adhesive to achieve precise and firm electrical contacts without heat, thereby eliminating the need for soldering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soldering is used to attach the flexible circuit to the conductive elements, then reliable electrical contact is achieved, but the assembly process becomes time-consuming and labor-intensive
Solution Approach 1:
The patent extracts and eliminates the soldering process from the assembly method, replacing it with a direct mechanical and adhesive bonding approach. The flexible circuit is attached to the conductive elements through epoxy adhesive and mechanical pressure without using solder, thereby removing the time-consuming and labor-intensive soldering step while maintaining reliable electrical contact.
Solution Approach 2:
The patent replaces the thermal-mechanical soldering system with a mechanical-adhesive bonding system. Instead of using heat and molten solder to create joints, the invention uses epoxy adhesive applied under mechanical pressure to bond the flexible circuit to the conductive elements, achieving both reliability and productivity improvements.
2Strength
If lead soldering is used for transducer manufacturing, then strong bonding is achieved, but lead contamination occurs violating ROHS regulations
Solution Approach 1:
The patent extracts and eliminates lead and lead-containing solder from the manufacturing process. By completely removing the soldering step and replacing it with epoxy adhesive bonding, the invention achieves strong bonding without any lead contamination, thereby complying with ROHS regulations.
Solution Approach 2:
The patent changes the bonding mechanism from metallurgical bonding (soldering) to chemical-adhesive bonding (epoxy). This parameter change in the bonding method eliminates the need for lead while maintaining or even improving bond strength, as the epoxy adhesive provides both mechanical strength and electrical insulation.
3Reliability
If soldering process is used, then permanent electrical contact is achieved, but manufacturing cycle time increases to 55 minutes
Solution Approach 1:
The patent applies preliminary action by pre-positioning the flexible circuit on the conductive elements using epoxy adhesive before final curing. The adhesive is applied and pressed in advance, allowing the components to be bonded in a single step without requiring subsequent soldering operations, thereby reducing the manufacturing cycle time while ensuring permanent contact.
Solution Approach 2:
The patent replaces the time-consuming thermal soldering process with a faster mechanical-adhesive bonding process. The epoxy adhesive bonds the flexible circuit to the conductive elements through mechanical pressure and chemical adhesion, eliminating the need for soldering equipment, heat treatment, and cooling time, thus reducing the manufacturing cycle from 55 minutes to a much shorter duration.
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 method significantly reduces manufacturing cycle time from 55 minutes to 25 minutes and eliminates lead contamination, ensuring compliance with ROHS regulations while maintaining reliable electrical connectivity.
Implementation Method 1
a piezoelectric ceramic transducer array
Implementation Method 2
employing epoxy as an adhesive to achieve precise and firm electrical contacts
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Disclosed is an NDT/NDI probe array and manufacturing method. The probe array includes a sheet of flexible circuit 10 with a plurality of lower pins 102 and corresponding, electrically connected, upper pins 104. The probe further comprises a backing block 12, a layer of piezoelectric ceramic 16 having a plurality of conductive elements 162, a matching layer 18 and a frame 14. An adhesive material such as epoxy is applied to the circuit, the backing, the ceramic and the matching layer, and all are aligned and stack pressed at least partially into the frame and permanently bonded in such a fashion that each of the lower pins of the flexible circuit is firmly and permanently in contact with a corresponding one of the conductive elements of the ceramic.