Projectduur: Circa zes maanden
Projectvorm: Detachering
Periode: 2008/2009
Aktiviteiten: Schemadesign, PCB layout, prototyping, bouw testers, firmware
TechnologieŽn: DXP, bed of nail, H8

Omschrijving:

Om de kwaliteit van geprocuceerde PCB assemblies te kunnen borgen zijn er diverse testers ontwikkeld die bij de EMS ingezet worden om boards functioneel te testen, en waar nodig van firmware te voorzien en/of af te regelen. De testers zijn gebouwd op basis van GPS Prueftechnik wisselkasten en -adapters. Bij deze opzet bevat de kast een standaard 24V power supply, serieele poort en USB aansluiting. De wisseladapters bevatten het pennenbed, de testcontroller en eventuele extra elektronica. Hoewel de wisseladapters vrij makkelijk uit te wisselen zijn, is er bij dit project voor gekozen om de adapters elk van een eigen kast te voorzien.

Totaal zijn er 9 verschillende kasten ontwikkeld, waarvan 4 met automatische RF afregeling en testen. Elke tester is in drievoud gemaakt; twee voor leveranciers (ivm dual sourcing) en een extra voor interne kwaliteitscontrole en als backup. Het bedraden van de pennenbedden is nog klasieke wire-wrap techniek.

Test controller:

GPS adapter case Until now, testing of production printed circuit boards (PCB) is usually done using some dedicated electronics, which is mounted under the bed of nails tester. Depending on requirements of the test, additional test and measurement devices may be needed. Some specific test applications use other boards from the target system to provide the stimuli and readback of data. One of the tests only consists of a bunch of loopback wires so that the board under test can test itself.

Both of these test approaches, although reasonably simple, easy to understand and usually quite reliable have some drawbacks. When a board under test has to test itself, than one must assume that the microcontroller core system is working correctly. Also, most signals are wired in loopback configuration, which means that problems can be identified to a single location. When boards are tested with some additional electronics and test equipment, then there is no easy way of keeping track of tests performed, especially not when operator actions or checks are needed as part of the test procedure.

Hence this new test controller board. This board consists of the same microcontroller as the more sophisticated production boards. So many of the existing software can be reused as well, which means that PC communication is already available including the possibility to have record based test result logging on the PC. Most of the microcontroller pins are equipped with protection circuits and voltage dividers or buffers where needed so that the microcontroller can be connected to the board under test in a reasonably safe way.

Because of the large variation in test signals needed on all the different boards, a provision is created on the test controller to enable customized piggyback modules. This enables a test system to carry other signals as well, such as higher voltage switches or optical inputs.