How a Smart Card is Made – Part 1: Smart Card Module Production

By | March 14, 2017

This four-parts essay aims to provide students, people involved professionally in the Smart Card Industry, businesses interested to invest in a smart card production / personalization facility, startups and consumers, the basic information on the industrial smart card manufacturing process.

There are many different processes and production technologies that are utilized to produce a smart card, here I am going to briefly explain some of the most popular in the industry.

The sequence of the process steps is also purely indicative as – different process – lead sometime to difference sequence of the manufacturing steps.

For the sake of clarity I have voluntarily omitted production steps, processes, techniques, features considered trade secret or confidential within the smart card industry.  

The manufacturing process is explained for the following popular smart card applications:

The process of smart card manufacturing can be divided in four main stages:

  1. Smart Card Module Production
  2. Card Body Production
  3. Card Personalization
  4. Card Fulfillment

As of time of writing, March 2017, STMicroelectronics, Shanghai Huahong Integrated CircuitSamsung, NXP, Infineon and Toshiba  are the only smart card chip suppliers  in the market with fully owned semiconductor fabrication plants. STMicroelectronics is the only company in the market to cover the full smart card production cycle, from the silicon wafer manufacturing to the card fulfillment.

1 – Smart Card Module Production


Silicon Wafer Manufacturing

The microcontroller (MCU) that power a smart card is produced in a semiconductor fabrication plant also known as “fab” were many different kind of integrated circuits are manufactured. Smart cards chips are produced in large quantities mostly using photolithography process and hundreds of them populate a single silicon wafer. When using ROM-based smart card chips the Card Operating System and sometime also some applications are permanently “burned” into each single chip of the silicon wafer. This production process produces mass volume of chips all identical among them.

The wafer is going trough a series of quality control checks and the chips showing anomalies are individually marked.

 


On Wafer Initialization

This optional step allow to activate and pre-personalize the chips while they are still on the silicon wafer. Typical activities of on wafer initialization includes:

  • Key diversification
  • Card Operating System initialization
  • Card Operating System pre-personalization
  • Application loading
  • Application initialization

The on wafer initialization is a service offered by the silicon chip manufacturer and allow to significantly reduce the card personalization time.


Silicon Wafer Dicing

The wafer dicing process separates the chips from the wafer by mean of mechanical sawing or laser cutting. Before the cutting  each wafer is attached on top of a thin adhesive tape to avoid that chips moves during the cutting process. When the chips are separated from the wafer they are referred as dies.

Wafer dicing process.


Microconnectors (Production Material)

The contact pads of a smart card are referred in the industry as “micro connector”. The can be customized according customer design and they are plated – using the electroplating process – with precious and semi-precious metals such as gold, silver or palladium.

Back side of a 35mm tape with smart card micro connectors.

According to the application need they can have six or eight pins. The micro connectors lay on a flexible substrate made of various materials such as EGT (epoxy glass tape), Copper-clad (epoxy glass tape + copper), PI (polyimide), PET (polyethylene terephthalate), PETG (polyethylene terephthalate glycol-modified), PC (polycarbonate), PVC (polyvinyl chloride) or Teslin.

Smart Card Micro Connectors.


Die Bonding

An adhesive like epoxy glue is dispensed on the pads area (lead frame) of the micro connectors.

Application of epoxy glue on micro connector.

An automated machine pick the non-marked dies from the wafer and place them on the micro connector.

Die bonded on micro connector.

An inline thermal curing allow the epoxy glue to dry creating a very strong bond with the chip and the micro connector tape.  At the end of the process the film is rolled up.


Wire Bonding

The exposed contact pads of the die are electrically connected to the corresponding contact pad of the micro connector using an extremely thin (about 30μm) gold or aluminium wire. The wire is permanently attached to the pads using the Thermosonic Bonding process.

Detail of a Ball Wire Bonding on die.

For smart card chips the following Thermosing Bonding techniques are utilized:

Detail of a Wedge Wire Bonding on die.


Chip Module Encapsulation

To prevent breakage of the sensitive wire contacts and the chips themselves from mechanical and environmental stress adhesives are used as encapsulants.

Diagram of chip encapsulation with resin.

The UV-curing epoxy resin is dispensed at high speed with a fully automated machine and they are hardened (curing) by means of UV light or UV light plus heating.

Encapsulated chips on film.

 

An encapsulated smart card chip using a semi-transparent resin.


Tape Inspection

The tape is visually inspected and non-compliant modules are marked.

A non compliant module is marked with a small hole.


Electrical Test

The tape is undergoing an electrical test where each smart card chip is powered and basic I/O test are performed. The faulty modules are being marked.

A SPEA Smart Card Module Test System. This system is also able to perform chip initialization and module punching.


Chip Module Initialization

The micro modules that were not marked during the  Tape Inspection and the Electrical Test are individually initialized and some time pre-personalized. The initialization process can loads into the EEPROM or Flash memory a large number of items including:

  • Chip serial and batch number
  • Card Operating Systems parameters
  • Card Operating Systems patches
  • Masked Applications parameters
  • Card Operating System (for Flash Based chips)

A machine performing modules initialization.

Some smart card chips also offer a special area of memory called OTP (One-Time Programmable) where boot code, encryption keys, configuration parameters or small software routines are stored during the Chip Module Initialization. Once the OTP memory has been programmed, it retains its value upon loss of power.


Ship to Card Body Production

The flexible carrier of the modules is winded into a non-conductive reel and packaged securely to protect it from dust and possible interception during shipment.

Next part: 2 – Card Body Production.

The process diagrams are available in a print-friendly PDF file here.

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