The present invention concerns electronic modules intended particularly to be fixed in electronic units in the form of cards, comprising a medium with at least one side provided with contact pads and a microcircuit which is fixed on said medium and which comprises exit hubs, each connected to a contact pad on the medium.
Electronic systems in the form of cards comprise, in particular, integrated circuit cards, also called chip cards, along with electronic element media for televisions, VCR""s, etc. A chip card comprises a card body and a module comprising the chip integrated within the body of the card. A chip card module comprises a medium, generally made of epoxy glass, with a metal plated surface in order to provide contact pads and a chip which is glued to the other side of the medium and which includes exit hubs on its outer side. Connection holes in the medium allow for passage of connecting wires which connect exit hubs to contact pads.
The connecting wires, made of stainless metal such as gold or aluminium, are soldered using various technologies such as soldering via ultra-sound or thermocompression which requires later coating (xe2x80x9cglob topxe2x80x9d) of the connecting wires with a resin to protect them. It is sometimes necessary to first fix a retaining barrier for the resin, such as a metallic or silicon ring, to the medium.
The mass of the resin is deposited in a non-controllable way and, when it is polymerized, it forms a very thick drop which exceeds the height of the chip card specifications. A milling operation is therefore necessary to reduce the thickness of the module to the required value. This milling operation can damage the module and is the main cause of production rejects.
In the body of a chip card, a cavity is made which is to receive the module and which must be relatively deep in order to receive a thick module. The thickness of the body of the card at the cavity is low, leading to significant deformation when the body of the chip card is bent, thus limiting the reliability and the working life of the card.
In addition, polymerization of this drop of resin provokes swelling of the module. This swelling can lead to deterioration of chip card readers.
The main purpose of the invention is to provide a shorter electronic module in order to eliminate the above mentioned problems.
An electronic module according to the invention has connections between the exit hubs and the contact pads that are made of a cord of an adhesive conducting substance which conforms to the profile of the medium.
These connections do not require a protective coating, allowing for reduction in the height of the module. Production is thus simplified and in particular the milling operation is eliminated, substantially reducing the rate of production rejects.
Preferably, the conducting substance is an isotropic conducting glue. A metal deposited by screen printing can also be used.
If the medium has connection holes, these are filled with the conducting substance. The medium may have two sides provided with contact pads and the connections are made directly on two sides without using the connection holes. Preferably, one of the sides of the medium is covered with an activatable adhesive film. This is an additional protection for the microcircuit and makes it possible to simplify the fixing of the module into the body of the card.
The microcircuit exit hubs may have connection bumps in order to reduce contact resistance.
Another aspect of the invention is a method for making an electronic module, in which the cord is made by depositing a viscous conducting substance. This technique of depositing using a syringe or similar device is rapid and easy to use.
In another aspect of the invention, a chip card has at least one electronic module of the previously mentioned type.