Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-03-04
2001-10-23
Maki, Steven D. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S295000, C156S323000, C361S737000
Reexamination Certificate
active
06306240
ABSTRACT:
The present invention relates to a method for making smart cards, of the type having a card body and an electronic module, and cards obtained by implementing the method.
Of the existing methods, a method is known of furnishing a card body with a cavity, an electronic module having principally contact pads and a semiconductor chip containing an integrated circuit, and of securing the electronic module in the cavity with gluing means such as a cyanoacrylate glue. In general, the gluing operation is divided into a prior operation in which the module is inserted into the cavity, and a pressing operation of a is predetermined length.
However, practical implementation of such a method, usually called “encartage” in French, on an automated industrial scale, which requires separate sequenced operations carried out at different stations, and transferring cards from one station to the next at high speed, on the order of several thousand cards an hour, leads to various problems affecting the quality of the finished product.
In particular, it has been found that the cards obtained by gluing using the operations listed above often have major drawbacks.
The principal drawback is incorrect centering of the module in the cavity. Despite correctly centered insertion of the module in the cavity, it has been found that after gluing some modules were off-center, i.e. had shifted from their initial insertion position. Typically, incorrect centering was slight rotation, or translation, or both at the same time inside the cavity, or in extreme cases outside the cavity with the contact pads having one edge overlapping the surface of the card body.
It has been found that the incorrect centering results in particular from forces produced on the card while it was being moved from one station to another, particularly sudden acceleration or deceleration forces brought about by the card leaving the insertion station and stopping at the pressing station, respectively.
Incorrect centering can also result from residual constraints present in the module which tend to produce a slight upward curvature. In this case, there is a risk of the module popping out of the cavity with each acceleration or deceleration referred to above.
Defects relating to poor adhesion of the module to the card body have also been found. In these situations, the card cannot meet the mechanical strength criteria imposed by current standards (ISO and AFNOR) for bending, twisting, and separating forces.
It is accordingly necessary to solve these problems without decreasing production rates.
The present invention relates to a method of gluing an electronic module into a card body that can be compatible with automated very-high-speed industrial production without thereby generating defects involving module centering or adhesion.
For this purpose, the present invention relates to a method for making electronic module cards of the type having a card body with a cavity, an electronic module whose dimensions match the cavity, and a glue of the cyanoacrylate type, and having steps wherein the gluing means are deposited in the cavity, the module is inserted into the cavity in a substantially centered position, and the glue is pressed between the card and the module.
The method is characterized in that the glue is deposited in a quantity enabling a gluing area of between 50 and 100% of the area of the cavity to be covered, after pressing, at a temperature of 15 to 30° C. and a relative humidity of 50 to 75%.
Because of these provisions, the method is defined in terms of environmental conditions that could be compatible with high-speed industrial implementation. The defects of poor glue adhesion and risks of fouling the dispensing means, and the risks of static electricity explained below, are avoided in particular.
The quantity of glue satisfies the requirement of having a sufficient adhesion area to meet the mechanical strength criteria referred to above, and the requirement of holding the module sufficiently firmly when subjected to forces tending to push it off-center while it is being transferred or until the glue is pressed.
Better results can be obtained when the above area is between 60 and 80%, the temperature is between 18 and 24° C., and the relative humidity is between 50 and 75%.
The quality of gluing can be improved while ensuring satisfactory module holding when the above area is approximately 70%, the temperature is approximately 20° C., and the relative humidity is approximately 55%. Under these conditions, the glue used has an open time of approximately 60 seconds.
According to another characteristic, the method had an additional step in which the lower surface of the module is moistened with alcohol prior to being inserted into the cavity.
The purpose of this feature is to artificially create points of adhesion of the cyanoacrylate glue to the module, enabling it to better maintain its centered position while being transferred from one station to another at high speed.
According to another characteristic, the module is inserted in a time of 300 to 600 ms.
This time allows the glue to create still more points of adhesion to the lateral surface of the module for better maintenance of its centered position during transfer. In this way, the method according to the invention allows glue to be deposited at very high but fully controlled rates.
According to another preferred characteristic, the glue is disposed in the form of at least five glue dots, a central dot composed of a drop known as central drop weighing between 0.002 and 0.004 gram, and four lateral dots, each lateral dot composed of a drop weighing between 0.0005 and 0.0015 gram.
These values give the module a good hold while it is being transferred. Also, deposition in this form rather than another form, for example a bead in the same quantity, has been shown to be faster. For optimum holding, these values are approximately 0.003 and 0.001 gram respectively.
Better gluing quality is obtained when the four lateral glue dots are deposited after the central dot is deposited.
According to another characteristic, the method carries out the final pressing with pressing means that apply pressure only to the periphery of the contact pads.
Due to this arrangement, the pressure necessary for obtaining a given glue thickness can be applied and good-quality module adhesion can be created with no risk of creating pressure strains in the semiconductor chip, that could damage it.
The present invention also relates to an electronic module card obtained according to the above method.
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Electronique Radio Plans, No. 535, Jun. 1992, pp. 50-52. Gueulle, Patrick.: “La Fabrication des cartes a puces chez gemplus”.
Gemplus
Haran John T.
Maki Steven D.
Plottel Roland
Upham John D.
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