Dual Interface IC Card Soldering via Electromagnetic Induction
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Solution Overview
Problem
Existing dual interface IC cards face challenges in achieving reliable conduction due to thermal, mechanical, and chemical stresses associated with the use of conductive films or resins in contact formation between the micro module and antenna.
Innovation Solution
A method using a conductive eutectic alloy, such as bismuth-tin, for soldering the micro module to the antenna terminals, where the melting temperature is reached through electromagnetic induction, forming stable electric contacts and ensuring mechanical resistance and oxidation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive films or resins are used to form contacts between micro module and antenna, then conduction is achieved, but thermal, mechanical, and chemical stresses compromise the stability and reliability of the connection
Solution Approach 1:
The patent changes the material parameter from conductive films or resins to a eutectic alloy composition (specifically bismuth-tin alloy with 58% Bi and 42% Sn), which has a lower melting point and forms a more stable conductive connection that resists thermal, mechanical, and chemical stresses
Solution Approach 2:
The patent uses a composite approach by combining the eutectic alloy with the plastic support material, creating a integrated structure where the alloy forms conductive bumps that are mechanically and thermally bonded to both the antenna terminals and micro module contacts, providing superior stress resistance compared to separate film or resin layers
2Reliability
If soldering paste is applied to antenna terminals and micro module contacts, then stable electric contact is formed, but the plastic support may be damaged by high melting temperatures
Solution Approach 1:
The patent changes the temperature parameter by selecting a eutectic alloy with a melting point of approximately 138°C (lower than conventional solder), which is sufficient to form stable conductive bumps without exceeding the thermal tolerance of the plastic support material
Solution Approach 2:
The patent replaces conventional thermal conduction heating with electromagnetic induction heating using a solenoid, which directly induces eddy currents in the conductive alloy to achieve rapid and localized melting without heating the surrounding plastic support to damaging temperatures
3Reliability
If conventional soldering methods are used, then conductive connections are formed, but the process is complex and time-consuming
Solution Approach 1:
The patent replaces complex multi-step conventional soldering processes with a single electromagnetic induction step, where the solenoid directly induces melting and bonding of the eutectic alloy in one operation, significantly simplifying the manufacturing process and improving productivity
Solution Approach 2:
The conductive alloy paste automatically forms uniform conductive bumps through electromagnetic induction heating, with the heat generated directly in the alloy material itself, eliminating the need for external heating fixtures, temperature control systems, and complex process monitoring
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 provides stable and durable electric conduction that is resistant to thermal, mechanical, and chemical stresses, while maintaining the integrity of the plastic support, offering improved mechanical affinity and resistance to oxidation and humidity.
Implementation Method 1
The melting of the alloy is obtained through electromagnetic induction by using a solenoid
Implementation Method 2
US 2008/283615 A1 discloses a method for producing an IC card of the Dual Interface type comprising the steps of arranging a plastic support comprising a recess, for housing a micro module, housing in the IC card an antenna having a first and a second pad of connection to the micro module arranged in the recess, and distributing a soldering paste on the first and second pad so as to form a first and a second conductive bump with contacts of electric connection of the micro module. US 2007/ 279230 A1 refers to soldering by applying an electrical current between contacts A and B in fig. 2B, thereby causing resistive heating (cf. par. [0039]).
Implementation Method 3
distributing a soldering paste on said at least one first and one second pad, so as to form a first and a second conductive bump with electric connection contacts of said micro module; said method being characterized in that it further comprises the steps of: distributing, along the whole perimeter of said micro module or of said recess, a layer of non conductive glue; positioning the micro module in said recess with the contacts axially aligned to the terminals of the antenna; executing a reflow of said soldering paste to form said first and second conductive bump
Data Source
AI summary
Method for realizing a dual interface IC card (50) comprising the steps of: arranging a plastic support (51) comprising a hole (56) or a recess, for housing a micro module (52); housing in the IC card an antenna (55) having at least one first and one second terminal or pad (p51, p52) of connection to the micro module (52) arranged in the recess (56); distributing a soldering paste on said at least one first and one second pad (p51, p52), so as to form a first and a second contact conductive bump (59a,59b) with electric connection contacts (c51, c52) of said micro module (52); distributing, along the whole perimeter of said micro module (52) or of said recess (56), a layer (58) of non conductive glue; positioning the micro module (52) in the recess (56) with the contacts (c51, c52) axially aligned to the terminal (p51, p52) of the antenna (55); executing a reflow of the soldering paste to form the first and the second conductive bump (59a, 59b).