BY DR. MICHAEL E. WERNLE MEINEN ZIEGEL & CO. GMBH
Introduction
During the last several years the way of manufacturing a contactless
smart card has changed dramatically. For the first time, various manufacturing
technologies influenced by other parts of the electronic assembly industry
entered the smart card market.
Recently, new developments have offered market solutions which are
also suitable for card manufacturers with less production experience
and a lower development budget.
The following article shows roughly the process flow of manufacturing
a contactless card and describes in detail a new manufacturing process,
called Cut Clamp Technology (CCT), to connect a lead frame chip module
to an antenna structure. It draws its advantage out of the simple principle
of offering the market a highly reliable production process with highest
outputs.
The Production of Contactless Smart Cards
Production Chain
The typical contactless smart card consists of a chip module and an
antenna, both encapsulated in a card body. If the chip module is mounted
on an antenna sheet (plastic sheet with etched, printed or embedded
antenna structure on it), it is called an "electronic inlet".
The following block diagram shows the basic steps of the Contactless
Smart Card production, called CSC Contactless Smart Cards and the position
of CCT inside this structure.
Technology overview
Today the contactless smart card market is divided into some major
segments. The table above gives a short overview:
The segment with 13,56 Mhz cards like Siemens/Philips Mifare is, at
this time, the most important stream and creates the highest demand
from the market to offer highly reliable and easy to use solutions for
card manufacturers.
Design Targets
The operational target of the process development was a user-friendly
process to manufacture electronic inlets for the manufacturing of contactless
smart cards. This process can be used in the manufacturing plant of
a supplier of semifinished products, which supports card manufacturers
with components (chip modules, antennas, electronic inlets); as well
as in the production chain of a card manufacturer.
Flexibility and an excellent price/ performance relation was a must.
Designing such manufacturing equipment with a wide range of production
capacity, as well as a very attractive entry level regarding the initial
price, was an additional challenge.
The efforts were focused on the mainstream part of the production chain,
i.e. printed or etched coil and hot lamination. For 13,56 Mhz systems
(the most important part of the todays market), it was also one of the
key issues to find a process which fits to the existing manufacturing
technologies like hot lamination.
The CCT Manufacturing Process - Basic Steps
The manufacturing/mounting process consists of the main steps described
below:
- Preparation of the chip modules for the mounting process
- Mounting the chip modules on the antenna sheet 1.
Preparing the Chip Module
The chip module (1) based on a leadframe module has to be pricked twice
with a steel needle (2) & (3). The result is a module (3) with two
connection "crowns," which is prepared to be mounted on a
plastic sheet with etched antennas.
The picture above shows a connection "crown" made into a
Siemens Mifare leadframe chip module. Upon further processing, this
"crown" will form the connection between the chip module and
the antenna.
Above, the top view of a Siemens Mifare leadframe chip module with
two connection "crowns".
Mounting of the Chip Module
In the following process steps, an integrated bonding head combines
all steps in one integrated mechanical unit. In order to increase the
speed of a manufacturing system, two or more bonding heads are working
in parallel.
A stamp presses the "crown" into the plastic sheet, thus
causing the "crown" to cut through the plastic sheet as well
as the contact pads of the antenna.
The "crown" cuts through the plastic sheet as well as the
material of the antenna.
Then the "crown" is bent over the contact pads of the antenna
in order to create a reliable, mechanical connection.
The last step of the manufacturing process consists of pressing down
the connection "crown" to the antenna (pad).
Picture of Electron Microscope
The picture shows one edge of a connection "crown" of a lead
frame chip module.
Cross Sections
The pictures above and below show cross sections of a leadframe module
mounted on a PVC sheet with an etched antenna structure (copper).
Cost Comparison
The production cost differences between various technologies and manufacturing
solutions are caused by differences in the following values:
- Investment
- Yield loss
- Labor requirements
- Availability
- Material
A rough overview of the resulting production costs is given in the
following table. A combination of a printed coil with CCT technology
seems to be the most competitive solution at this time.
The lower costs are achieved through:
- A simple process
- A lower initial investment
- High yield rates
- No need of extra material (solder paste, insulation material, etc.)
Benefits
There are various advantages of this new approach, especially from
the process point of view. This process and new technology can be easily
integrated in a reliable piece of manufacturing equipment, which meets
the requirements of today's market.
What are the advantages of this new technology? First, only a few mechanical
process steps are required to produce the final inlet. No heat is applied,
as in welding or soldering processes.
No isolation layer is necessary between the module and antenna sheet,
because the module is mounted from the backside of the plastic sheet,
which acts like the isolation layer. Due to the reduction of the number
and complexity of process steps, the whole production cycle becomes
as simple as possible and extremely cost competitive.
The resulting inlet is ready for further processing using traditional
hot lamination presses or a cold bonding process like Coolpack developed
by Meinen, Ziegel & Co.
Various kinds of antenna sheets (etched, printed or embedded antennas),
sheet materials, and antenna/sheet layouts can be used. The system can
be easily adapted to any particular requirement since all production
and test parameters can be freely programmed as needed.
Summary
Process and Technology Benefits
- Only three mechanical process steps necessary
- No heat applied during the whole manufacturing process
- No sensitive isolation layer between module and antenna sheet necessary
- No need for extra materials (solder paste, conductive glue, insulation)
- CCT works with different sheet materials (PVC, ABS, PET, Mylar,
Kapton, Nomex)
- Inlet ready for usage in the Hot Lamination Process or the Cold
Bonding Process
Manufacturing Benefits
- Economically attractive because of highest flexibility
- No need for extra materials (solder paste, conductive glue, insulation)
- Different antenna designs available, also for embossed cards
- Multiple contacts possible (more then two)
- Inlets suitable for hot lamination or the Cold Bonding Process
- Equipment available for production on a wide scale (300 - 2000 units/hour)