A. Campbell McCracken

Freelance Journalist and Consultant


Smartcards Require Smart Testing

Although behind other countries in starting, the UK is starting to embrace the smartcard world in a big way. Trials for electronic purse applications have been running in Swindon for over a year (see Smartcard Applications) and have extended to UK universities, and now BT has launched their long awaited replacement for the phonecard [Electronics Times, 18/7/96]. The likely scale of the change in technology brought about by the smartcards will result in a corresponding requirement for new test capability for card manufacturers and issuers.


There are two main types of smartcards currently available. Memory cards are the simplest and least expensive cards. They combine intelligent EEPROMs with security logic and high security authentication. The second kind of card, the processor card, is more expensive than the memory card and features processor based file and directory structures, making it ideal for data storage applications.

The new BT phonecard is of the memory card variety, and is based on the Siemens SLE4438 or 'Eurochip' technology. These third generation cards, containing a 221-bit EEPROM and a 16-bit masked programmed ROM, are once programmable or 'throw-away'. This compares to the French banking Smartcard which has a 1K EEPROM, 3K ROM and 128 bytes of RAM. BT now have 60,000 public phones capable of accepting the new phonecard to be available.

Smartcard Standard Definition

The standard smartcard electrical interface is defined in ISO 7816. The memory cards use a simpler protocol than the one defined in the standard and are relatively easy to access. The waveforms are TTL with a minimum timing requirement of a 10mS clock period.

Processor cards, on the other hand, conform fully to ISO 7816 which defines the communications protocol, and electrical and mechanical interfaces. The protocol can be described as RS232 with TTL levels with a shared (half-duplex) transmit / receive line. A stable 3.579545 MHz clock is applied and this is internally divided by 372 to give a 9600 bit per second communications rate.

Smartcard Production

There are three main stages at which testing will be required in the smartcard life story. First, the smartchips are tested on the wafer after fabrication. Failing chips are marked and discarded as soon as the wafer is split. Passing chips are bonded up into modules ready for embedding into plastic cards, or as a semiconductor die for customer packaging. Many smartcard manufacturers buy the smartchips rather than fabricate them themselves.

The remaining two stages of test are therefor usually carried out outside the specialist fabrication houses. (See Figure : Two test stages). Smartchips are fixed to the carrier modules on 35mm tape. The modules contain the smartcard contact pads, and the leads from the chips are bonded to them. The leads are also all connected together at this stage for ESD protection. Typically chips are mounted on the tape in pairs with three common bond points between each pair of chips.

The smartchip modules are tested at this stage before they are mounted on to the cards. The testing is needed to verify that the chips are still functioning after the mechanical processing. The value of the assembled card will vary according to the card types, from a few tens of cents for simple memory cards, to a few tens of dollars for processor cards. With expected yields of smartchips of the order of 95% and quantities for any particular customer of the order of tens of millions, a simple calculation gives the value of the 'dead' cards to be of the order of millions of dollars. If the faulty chips are found before mounting, the cost of 'dead' chips can be reduced to the order of tens of thousands of dollars.

Figure : Two test stages

The test requirements are electrically simple at the pre-mounting stage. The smartchip modules are available on a 35mm reel sandwiched between the 35mm film and a protective layer. The film has sprocket holes along each edge for locating the tape in the handling equipment. Before any testing can take place the protective layer has to be stripped away, and once testing has been completed this layer can be reapplied. (See figure : Smartchip Test Station.) Also, before testing can take place, the test station has to punch out the bonding points connecting all the smartchip leads together. Then the chips can be tested to ensure that they are still alive.

At this stage the test is typically a simple one which verifies the manufacturers identification while in issuer mode. (In this mode, the chip is protected against fraud with a transport locking code known only to the manufacturer and issuer. This code must be correctly presented to the card before personalisation can take place, otherwise the card is locked forever.) By performing this test all five of the device pins of the smartchip are tested for functionality. This gives the manufacturer a reasonable level of confidence that the smartchip is alive and well and has been correctly mounted on to the contact pads.

Figure : Smartchip Test Station

The tests are performed on 20 devices at a time to boost throughput. Contacts with the smartchips modules are made through a bed of nails fixture. This uses dome-headed nails to minimise any damage to the smartchips gold plated contacts. The smartchips on the 35mm tape are fed through the test head by a motorised, dual continuous band transport system. The tape position is optically sensed through the sprocket holes to align the contact pad centres with an accuracy of +/- 0.25mm. Once the 20 devices have been tested, any faulty devices detected are marked by punching a hole in one of the device contact pads. This hole can be detected by an optical sensor at the mounting stage and the chip discarded.

The complete test station consists of six main elements, four of which operate independently of each other, with tape buffers being used to connect the four elements together. The level of tape in each buffer is topped up when it falls below a predetermined limit. The six elements are the de-reeler, the disconnect punch, the testhead, the M505 functional test system, the failure punch and the re-spooler.

Assembled Cards

The second major test stage takes place on fully assembled cards. The cards carriers are already prepared with the relevant artwork before the smartchips are mounted on to them. The test at this stage is a conformance or interoperability test, performed on a batch test basis and is used to characterise each batch of smartcards. A characterisation test is essential because the value of each card does not simply consist of the cost of manufacture. Since the card will also be used as virtual money it will contain a value of, say, $50. The eventual card owner and user would want to be able to take his card to any reader in the country, at any time of day or night, summer or winter and expect to be able to get access to the full value of his stored money.

Figure - Interoperability Tests ensure that each Smartcard can be used anywhere in the country, summer or winter, day or night

The effects of interoperability can be simulated by varying the key operating parameters of the card, i.e. the supply logic, the threshold levels and the access timing conditions. This requirement puts the assembled card tester in a class above the simple testers using standard card readers. These simple testers are unable to vary these parameters. By interfacing the tester to an environmental chamber, there is also the possibility of testing the cards under a range of temperature and humidity conditions.

The test hardware at this stage is effectively imitating the functions of the card reader which would normally be found on a payphone or cash machine, but the tests which can be performed at this stage need not be limited to the normal transaction cycles. The tester could be customised to allow the card manufacturer to construct more complex test sequences. For example, a test sequence could consist of a number of subtests or subtasks, including presenting the card with valid or invalid transport locking codes, authentication and personalisation of the card, setting the counter start value representing the monitory value of the card. Since different cards will contain different information depending on their use, the card contents require a thorough checking for programming integrity and functionality.

Most smartcards will have an authentication process to ensure that the card is a valid one. Normally this would consist of a cryptographic challenge / response process. For security reasons, any test solution would not normally contain the challenge / response algorithm in software, but instead would use a processor smartcard inside the test fixture.

Other Test Needs

One of the next steps in the evolution of the smartcard will be the widespread use of contactless smartcards (which are accessed using induction or RF techniques) for transport and road tolling applications. The reported effective operating ranges of these cards will vary from 1m for cards operating at a frequency of 125kHz to 10cm for an operating frequency of 13.5MHz. Possible test requirements for contactless cards include power, range and susceptibility tests.

Because of the nature of the physical abuse most cards will experience during their lifetime (e.g. being kept in a wallet in your back pocket) cards will also have to be tested to ensure that they are rugged enough to withstand flexing in both vertical and horizontal planes and to a lesser extent, torsion.


Because of their complexity, interoperability and usage volumes, Smartcards require specialised testing to minimise the cost of faulty cards to the manufacturer and to the end user. Not only should the cards themselves be tested at several key stages, but the equipment which will be used with the smartcards has to be thoroughly tested too. MICAS, Marconi Instruments solutions group, can deliver electrical, RF and mechanical test solutions for standard and RF contactless smartcards, customised to customers' specific requirements.


I would like to thank Alan Whyte, former Marconi Instruments Applications Engineer, and Duncan Askew, Product Specialist for some of the background information for this article.


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