Quality

E.D.&A. controllers are used world-wide in custom-made applications. Excellent quality of these products is therefore extremely important.

This philosophy starts at the design stage: by putting very stringent demands on the design and by standardising. E.D.&A. is able to bring the quality of their products up to a very high standard.

Semi-finished products are placed with carefully selected suppliers who must satisfy our strict quality demands. E.D.&A. coordinates the production by these companies via an ERP software package. The types and brands of all components purchased by the suppliers are laid down by E.D.&A. In this way, E.D.&A. has complete control over the materials used.

Hardware

Own EMC lab

All electronic designs must satisfy strict EMC requirements under the EC regulations. Insensitivity to faults is an important requirement for each design, separate from the requirements imposed by the EC regulations.

E.D.&A. has its own EMC lab with state-of-the-art measuring equipment that is essential for fully testing an electronic controller. The equipment generates fault signals and examines whether the design itself is not radiating too much.

It is also examined whether the design continues to operate properly under a variety of conditions. What happens at very high or low temperatures? Do components in the design become too hot? What happens with high humidity? In some designs there are specific requirements for sensitivity to vibrations. E.D.&A. is able to place the design, possibly built into the final application, on a shaker.

What tests do E.D.&A. controllers undergo?

Automated Optical Inspection (AOI)

When the PCB has gone through the first soldering stage, i.e. the SMT (Surface Mount Technology) soldering, then the half assembled PCB already undergoes a first test. After all, the earlier a fault is detected, the faster the intervention to apply corrective measures to the process. In this test, detailed photos of the PCB are taken (by a machine) that are automatically compared to preset patterns. As a result the quality of the soldering is examined, the presence of the components is guaranteed and the imprint of the components can be verified. If irregularities are detected, the intervention of an operator is required. This operator then takes the final decision.

X-Ray

If complex (SMT) components that are difficult to solder are used (for example, BGAs or ball grid arrays), then an X-Ray machine can be used to check the soldering. However, this is not a standard test and is only done if the application so requires.

Flying probe test (FPT)

Hundreds of minute components all perfectly soldered? This is not realistic and that is why all printed circuit boards are individually checked with the flying probe test. A robot with measuring pins (probes) literally flies over the printed circuit board to checks that all the components are properly placed, have the proper value and are not defective. This machine can also detect short circuits on the board, even before the board has been connected to the voltage. This avoids components being damaged due to the incorrect fitting of other components, and the impact of the fault is minimal.

This test is sometimes done for PCBs that are only SMT soldered. Sometimes only once the conventional (through-hole) components are also fitted. This depends on the complexity of the PCB and is examined by the PCB developer.

It is important here that E.D.&A. already takes account of the limitations of these tests in the design phase, and ensures that the probes are all at the right connection points on the PCB.

In Circuit Test (ICT)

This test is an alternative to the FPT. A fixture with a pin bed is used here. This fixture consists of a "tray" with pins on the base and sometimes also on the cover: these are the probes (i.e. the pin bed). The PCBs are then placed in this fixture. The principle is that all tracks on the board have a connection to the pin bed. These connections are then connected to a measuring system. The same measurements are then done as with the FPT.

With an FPT, the probes move over the PCB, with ICT every measuring point has its own probe and the signals to be measured are connected in order to carry out the right measurements.

This test also requires the necessary attention during development to ensure that there are such connection points for the probes on every track. This test can also be carried out after the first soldering phase (SMT only) or after the second soldering phase (if through-hole components are also fitted).

First Functional Test (FT)

When the PCB has been completely soldered and when the passive tests have been done, then a first minimum test can be carried out on the live board. This is what E.D.&A. calls a "functional test". This examines whether the crystal is working properly, whether the microprocessor starts, the display works, the software version is the correct one, etc. Simple things that cannot be tested passively.

Active Burn In test (ABI)

Here again, this test can only be done after all components have been fitted. The PCBs are placed in a climate test cabinet, where the temperature varies from 0°C to 60°C according to a set programme. During this test, the products are automatically monitored functionally. As a result of these temperature shocks, poor or bad contacts are detected. Sometimes this test is only done at room temperature.

The main purpose of this test is to bring all components up to operating temperature for some time, in order to pick up early failures as a result of substandard quality of the components, even before the PCB gets to the customer.

Visual control

The earlier batch faults are found, the better. That is why spot checks are done for every delivery from the production companies. Based on all the tests done and experience with earlier problems, a list is generated of the points to watch and the components that have not yet been tested or only minimally so. On the basis of this list, and if need by a model, these components are visually inspected for their type, position and quality.

Functional end test

In order to guarantee optimum quality of the products supplied, a functional end test is finally done before delivering the PCB. This test consists of a visual inspection and a complete functional end test for every PCB. E.D.&A. tests all PCBs before they are sent to the customer.

The visual inspection is done according to a test sheet drawn up by the PCB designer. After the latest software version has been loaded (if required), the PCB will go through a functional test specifically designed for it. E.D.&A. always bears the costs of this test system itself in order to guarantee the quality of the tested PCBs. Only when this test has been successfully completed, an invoice can be made for the controller.

Continuous feedback between the people of the test department and the development department is important for these tests. The test sheets of E.D.&A. are continually adjusted on the basis of information from the testers and experience from the past or with other PCBs.

E.D.&A. also has a multifunctional test system: a UTS system (Universal Test System). This test system is almost exclusively used for the functional end tests of the standard controllers.

In the final assembly department of E.D.&A., the products are further completed to become end products according to the ongoing customer orders.

Software

The way in which embedded software is written and implemented has an enormous impact on the quality of your machine or equipment. E.D.&A. is fully aware of this. The software developers of E.D.&A. have an eye for recognising and picking up on possible fault-sensitive situations. Precautionary measures are taken in the software, and if an unforeseen fault nevertheless occurs, it is accommodated. Your application thus continues its stable operation.

By proceeding in a structured way during software development, the quality of the work supplied is substantially increased. For example, the E.D.&A. software developers use source code guidelines to structure the source code. The application of these guidelines gives the source code a uniform appearance. However, what is much more important is the fact that the imposed structure only allows those subsets and constructions of a language that are suitable for the programming of embedded systems. Using very modern and efficient tools, E.D.&A. ensures that the source code is automatically tested against the standards followed, which guarantees a very high reliability of the embedded software.

Furthermore graphic tools are used for the 'model-driven' design of certain software blocks in a control system. For the blocks in the controller where this technique is applied, the source code is automatically created on the basis of a model that is entered graphically. The automatic conversion from working model to source code reduces the risk of errors and also increases maintainability.

ESD

What is ESD?

ESD is a term with a negative connotation in the world of electronics. This three-letter word stands for ElectroStatic Discharge. Remember the crackle your hear when taking off a jumper, or - in the extreme - thunderbolts, for example. All these things are no more and no less than ElectroStatic Discharges. ESD is the physical phenomenon where a quantity of accumulated charge suddenly moves. Accumulated charge is of course not a stable form of equilibrium. When an electrical path is reached, nature will eliminate the accumulation in order to get closer to a stable equilibrium. When the accumulated charge is eliminated, the charges move, and this is the ESD current.

Why does the world of electronics fear it?

In electronics, the trend is to make components smaller and faster. By doing this, the quantity of current that the tracks in the electronic components can tolerate decreases. In practice, ESD currents can really damage electronic components.

There are two possible scenarios:

1. The ESD current damages the component so that it no longer works. Actually, this is the most favourable situation. A good functional test of the PCB will bring this to light, which will prevent this defective component being put into a machine or device.

2. The ESD current has damaged the component but not enough to introduce a functional defect. This is also called "latent ESD damage". Such damage cannot be detected in a functional test. Only later, when the operating conditions are different (for example when the component is at operating temperature, when the load is at a maximum, etc) the component will become permanently functionally defective. So the component will suddenly fail at a later stage without a clear attributable reason.

This latent ESD damage shows the importance of the correct implementation of preventive measures. Who after all wants to buy a product that fails, even though it has not been used incorrectly? At E.D.&A. we are aware of the ESD issue. Quality and customer satisfaction are our top priorities, so we do everything to keep the consequences of ESD to a minimum through preventive measures.

What preventive measures does E.D.&A. take?

The underlying cause of ESD damage is the undesired flow of accumulated charge. Then it is simple: avoid charge accumulating, and if it does so nonetheless, then we must ensure that it is carried away in a controlled manner without it being able to cause damage. We endeavour to realise these objectives in an EPA, i.e. an ESD Protected Area.

In practice, materials should be used that are not subject to the physical phenomenon by which charge can transfer from one material to the other by rubbing two different materials together (= the triboelectric effect). In the EPA, E.D.&A. therefore uses special workbenches, desk chairs, floors, clothing (overcoats), shoes, tools, etc.

Furthermore, E.D.&A. also uses suitable packaging materials that prevent electronic components from being damaged by ESD discharges upon contact. This is both during transport within the EPA of subcontractors, transport from the production companies to E.D.&A., transport within E.D.&A., and finally, transport to the customer where the controller will be installed.

What measures do you take?

Hopefully you are also aware of the importance of preventive measures to prevent ESD discharges. E.D.&A. imposes the necessary discipline on its staff to correctly follow the preventive measures. However, when our goods are unpacked on your premises, they are no longer under our control. It is therefore certainly not a bad idea to provide wrist straps or heel straps for the people who come into contact with the electronic equipment. In this way any accumulated charge can safely be eliminated, which prevents damage to the components.

Tracking & tracing

At E.D.&A. every PCB is given a unique serial number. With this serial number we can always reconstruct the history of the PCB concerned as of the moment that it comes into E.D.&A. With these serial numbers we can also guarantee that only successfully tested PCB's are sent to our customers. Our system makes it impossible to select a PCB for a customer if the status of this PCB does not indicate that it has been successfully tested.