Yelo System and Cell Manufacture

Analysis of the problem

In today’s manufacturing industry the emphasis is on shipping finished goods. In order to achieve this build time is kept to minimum and the stock of raw material kept to a minimum also.

In the electronics industry there is emphasis on a part of the production cycle which deals with the quality of product produced. This area is test. Currently there are two distinct philosophies that can be identified:

1. To check the build quality of the product, a test procedure known as In-Circuit (ICT) or Manufacturing Defects Analysis (MDA) is used. This process checks the board is built using the correct components in the correct orientation.

In some cases the belief is that if the board is built correctly it will work correctly

• To check the functionality of the boards a "Black Box " tester may be used. This is where a customised box of electronics is used to power up the board and carry out some basic functional tests to ensure the board works correctly

• The consequences of the above stategies can be as follows:

• The large ICT machines today focus primarily on testing ICT and largely neglect Functional testing. This can lead to problems where there is intelligence on the PCB in the shape of Processors and Microcontrollers. This can also lead to the use of secondary testers for functional test coverage.

In order to achieve good throughput, the test time can be very fast and this is necessary where several production lines converge one test station.

This in turn can lead to bottlenecking at peak production times. The cost of these test stations can be rather high meaning repeat stations may not be feasible. (In order to achieve cost effectiveness these testers may need to be fully utilised)

In todays industry the trend is for more complex boards to be built on ever smaller PCBs. This means that the test node access for ICT is getting less and less. In order to counter this new tools have been developed to achieve a good test coverage. These tools include: Boundary scan, Testjet and Optical Inspection (AOI).

• When a company is manufacturing a number of products simultaneously, the company may be operating a Cell Structure. This gives a flexible approach to manufacturing but generally requires a Test Station per cell. Generally the cost of ICT machines will be too expensive to implement in each station. This would require a low cost functional tester.

When sourcing a Functional Tester generally it can be approached from two perspectives. The first is to develop something in-house or in conjunction with a local engineering specialist. The second option is to go with a company who will supply off-the-shelf solutions.

The home produced tester can sometimes be seen a more cost efficient solution. However some of the hidden cost are not apparent in the overall cost analysis. The main disadvantage is that the system is very customised and may be hard to replicate or repair if the relative design personnel are not available.

When looking at off-the-shelf solutions it is possible to purchase standard hardware to produce a custom tester. It is also possible to get a complete turnkey for the application. This may seem expensive to initially implement but may prove reliable and cost effective over the life of the product.

Mindready (NI)'s solution to the problem

From the above we can identify that if a company can produce a tester which is off the shelf and also low cost, then the machine could be adapted for either or both test philosophies.

However as we are primarily interested in the idea of cell manufacture, we can immediately see an approach to acheiveing low cost and also generic test equipment.

Yelo 50

The Yelo 50 is the base system in the Yelo system series of ATE. As such it has all the software tools of its more powerful brothers. This means the software is compatible with all the Yelo systems. However the interface is slightly different than that of other models.

Fig.1 Yelo 50 showing d-type interface. (Fixture interface also available)

The main advantage of this system is the low cost. This allows a test station to be dedicated to a particular product whilst still maintaining full flexibility.

This system could be supplied as a complete turnkey which would include fixture and program, or to further save costs the fixture could be supplied in kit form and the program could be written in-house.

Yelo system OEM

In response to a previous request from a large manufacture Mindready (NI) developed an embedded system into a fixture for use in multiple cells within a manufacturing complex.

Fig.1 Embedded Yelo system cards shown at bottom of photograph

This system, known as the Yelo OEM has the Yelo system backplane installed inside a standard fixture. This will accept all the standard off-the-shelf cards for the Yelo system. This also means that the software is the same as that for the more conventional systems. Therefore the system seems to be a custom built tester but is in fact a standard generic type tester.

The fixture type for this product is recommended as the Cassette fixture. This further increases the flexibility of the system. However it is also possible to have the system installed in a manual fixture to keep costs to a minimum.

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