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APPARATUS FOR TESTING ADHESION STRENGTH BETWEEN A SMART CARD MODULE AND THE CARD BODY

IP.com Disclosure Number: IPCOM000008813D
Original Publication Date: 1998-Sep-01
Included in the Prior Art Database: 2002-Jul-16
Document File: 2 page(s) / 134K

Publishing Venue

Motorola

Related People

Kiron Gore: AUTHOR [+3]

Abstract

Modules used in smart cards are glued inside a milled or molded cavity. Two gluing processes are typically used - I) hot process using a hot melt glue film that is bonded with heat and pressure, and 2) cold process using Cyano-accrylate glue that is bonded with pressure only. In both cases, the strength of the bond is critical as it determines the life of the card in the field. Insufficient bond strength will result in the module lift- ing off the card surface and may even result in the module falling off. In contacted smart cards, bond strength of 25 lbs. is considered acceptable. The card is functional even when the module starts to lift off in the corners when subjected to bending. In case of combination smart cards, joint strength of at least 2X that of contacted smart cards is essential for maintain- ing the antenna connection and ensuring that the con- tactless operation is functional. Separation of the mod- ule from the card surface (particularly in the comers) will stress the antenna connection and may result in breaking the joint and thus causing an open circuit. Current bond strength testing methods have been designed with smart card applications in mind and are not suitable for combination smart card applications.

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MOTOROLA Technical Developments

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APPARATUS FOR TESTING ADHESION STRENGTH BETWEEN A SMART CARD MODULE AND THE CARD BODY

by Kiron Gore, Kevin Haas and Grace O'Malley

BACKGROUND

the epoxy to the gold surface of the top of the module which is approximately 25 Ibs. This pull strength is adequate for the contacted smart card applications. The pull stud to module joint breaks first when being pull tested. This only proves that the module to card bonding strength is greater than the epoxy joint strength of pull stud to module top surface. This strength is not adequate for combination smart card application, which requires pull strength at least 2X that of contacted smart cards. Soldering the stud to the top surface of the module will provide for higher bond- ing strength, however, it will also alter the thermal properties of the hot melt due to the heating involved. This will not provide accurate data.

  Modules used in smart cards are glued inside a milled or molded cavity. Two gluing processes are typically used - I) hot process using a hot melt glue film that is bonded with heat and pressure, and 2) cold process using Cyano-accrylate glue that is bonded with pressure only. In both cases, the strength of the bond is critical as it determines the life of the card in the field. Insufficient bond strength will result in the module lift- ing off the card surface and may even result in the module falling off. In contacted smart cards, bond strength of 25 lbs. is considered acceptable. The card is functional even when the module starts to lift off in the corners when subjected to bending. In case of combination smart cards, joint strength of at least 2X that of contacted smart cards is essential for maintain- ing the antenna connection and ensuring that the con- tactless operation is functional. Separation of the mod- ule from the card surface (particularly in the comers) will stress the antenna connection and may result in breaking the joint and thus causing an open circuit. Current bond strength testing methods have been designed with smart card applications in mind and are not suitable for combination smart card applications. PRIOR ART

Two test methods are currently used in the smart

card industry to test adhesion of the module to the card body, bend/torsion testing and pull testing. Bend/tar- sion testing subjects the card to bend and torsion stresses as specified by the ISO. This method, although adequate to provide pass/fail data and ensure that bad cards are not shipped to the customer, does not provide quantifiable data on bond strength. This method has risks of long term field failures if the bond strength is on the border between good a...