Manufacturing and CEM’s

In todays electronic manufacture there is a dilemma of how to manufacturing should be handled. Should it be sub-contracted or should it be manufactured in-house.

Generally the decision is dependant on volumes, complexity and logistics. However there is a current tendency to "farm out" the manufacturing process. This in turn leads another problem of test. The solutions can appear as follows:

Solution 1 - In-Circuit Test (ICT)

When building a product for todays market there is a necessity to test for build quality. A means of doing this can to carry out In-Circuit Test or Manufacturing Defects Analysis (MDA) This is where the board is analysed to check the components are inserted correctly and are indeed the correct components. The equipment available for this type of test is wide and varied.

The ICT machine can be a large, fast and expensive machine which can check all components including the digital packages. It can also be a small inexpensive machine with a lesser capability.

The decision for the type of tester can be led by the board complexity or cost.

Results of Solution 1

When purchasing an ICT machine there are 2 basic types to choose from. The first is a large complex type machine. These tend to be fast and expensive and as such will be used for several different product lines. This can lead to bottle-necking at the test area..

However the "High End Testers" as these are sometimes referred to can offer some benefits to a company looking for a subcontractor. Many sub-contractors will own their own ICT machines and the new product may need only a fixture and program. However the cost of time on the machine may be prohibitive.

The board complexity and density may require the use of a high end tester utilising tools such Digital In-Circuit, Boundary Scan and Testjet^®.

To look at the second test option, the cost of the lesser tester may be more attractive to a new product for production for a number of reasons. The cost of such testers makes it possible to dedicate a tester to a particular product. This in turn eliminates the chances of bottle-necking but also lend itself to Cell Manufacturing techniques.

The benefit of the "lesser" tester is that if the Contractor purchases the machine, this will allow for a lower cost option in test for the contractor to offer to other customers. It may also take some pressure off the larger test machines. If however the equipment is purchased by the owner of the product, the equipment can be controlled by them. This allows the product owner to take the manufacturing in-house should it be necessary. This can easily be directed to a contractor again if necessary.

As volume of the product increases it is relatively easy to duplicate a lower cost tester. This again lends itself nicely to the philosophy of cell manufacture, but also keeps the pressure off the higher spec test equipment.

Solution 2 Functional Test

Currently the trend in electronic products is to move to smaller PCB’s and to use an increasing amount of digital hardware on-board. This leads to problems in testing using ICT as access to all the required nodes is no longer possible. To compensate for the shortfall in the test or to eliminate ICT completely, Functional test can be employed. This is where test hardware is employed to power up the product and carry out "hot" tests. As with ICT there is two ways to approach this method of test.

As the product vendor has the most intimate knowledge of the product they may design a "Black Box" tester which mainly consists of custom electronics. Alternatively a local designer may be used.

An alternative to this is to purchase off the shelf hardware to functionally test the product. This gives a more flexible solution and again can be purchased by the CEM (Contract Electronic Manufacturer) or the OEM (Original Equipment Manufacturer).

Results of Solution 2

When building a "Black Box" tester a lot of the cost can be hidden giving a distorted view of the overall cost. Also these test boxes are generally built by a single person and problems can arise when personnel are shifted around or pursue other opportunities. This can leave the equipment unsupported and problems can arise when the test equipment develops faults. Similarly when the product changes or is modified the test equipment is also requires modification and this is not always easy

Using readily available test hardware prevent the above problems. Good support is generally available for such hardware.

Similarly repeat systems and spares are much easier to obtain in an off the shelf solution.

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