RoBAT
Test Strategy

The Robat Watertight Backplane Test Strategy
All four test types available from RoBAT.
The leading backplane test specialists

Our Products

The RoBAT Backplane Test Philosophy

Test your products – not the test equipment!

The staff at RoBAT work very hard to supply reliable test solutions so that your test system operator learns to trust the results he gets from the systems we supply. If the equipment says there’s a fault on a backplane, we want your operator to be confident there is!

Test Basics

A test system is typically made up of a number of sub-systems in series.  If any one of the sub-systems gives a problem, the whole process is compromised. For example the efficiency of a $500K+ test machine can be severely compromised by a few badly performing spring probes costing < $5.00 !

In a contactless test system such as AOI (automatic optical inspection) or X-ray inspection, the “system” amounts to just:

  •  Test machine + Test Program
    - and the vendor of the test system is often the supplier of the complete solution.

In a contacting test system (either flying probe or bed-of-nails electrical test) the system comprises:

  • The UUT contact (usually a spring probe) + test fixture + test machine + test program
    A test machine vendor may also offer to supply a test program.

However:

  • Test machine vendors do not make test fixtures and vice-versa
  • Test fixture vendors do not make spring probes and vice-versa
  • Spring probe vendors do not make test systems and vice-versa

This leads to a fragmented supply chain with no one supplier taking responsibility for a successful overall solution.

This is where RoBAT is completely different when it comes to backplane test – we design, manufacture and supply the entire chain so the buck stops with us!

RoBAT supplies and supports the full test system!

Market size and distribution

The test equipment options that are available for backplanes is severely limited by the size of the backplane manufacturing market – which is tiny compared to the pcba market.

The test equipment options that are available for backplanes is severely limited by the size of the backplane manufacturing market – which is tiny compared to the pcba market.

As a result, none of the major test equipment manufacturers make any equipment specifically for backplanes. This leaves small specialist companies like RoBAT as the only potential supplier to the large contract electronics manufacturers of backplanes (CEMs).

Surprisingly, this makes RoBAT the only company in the world designing/manufacturing and selling backplane test equipment with directly employed staff in all the significant backplane manufacturing markets – the USA, Europe and China.

RoBAT = Backplane test – that’s all we do!

There are 4 basic difficulties to addressing the backplane test marketplace:

  1. The market is very small but distributed around the world.
  2. All CEMs work on very on tight margins which tends to impede long term investment strategies.
  3. CEMs don’t pay for fixtures - they pass all fixturing costs onto their customers so have little
    incentive to improve test efficiency by buying new capital equipment.
  4. CEMs have cut most of their engineering staff that used to work pro-actively on test development.

The result is that most existing CEM backplane test equipment amounts to 10 years old DC bed-of-nails testers which simply cannot find many of today’s fault types.

There have been 4 big changes in the backplane marketplace over the last 10 years.

  1. Connector pitches have come down from 0.1” (2.54mm) to 0.031” (0.8mm)
  2. Pin quantities have gone up (some backplanes now have over 100,000 connector pins on them).
  3. Signal speeds have gone up meaning compliant pins are much shorter and softer.
  4. Digital devices like eproms are often now fitted to backplanes and require more than a simple DC test and often programming also.

In < 10 years, the backplane business has changed from:

0.1” pitch DIN and 2mm pitch Metrals – which were easy to test using spring probe test fixtures etc.
0.1” pitch DIN and 2mm pitch Metrals –
which were easy to test using spring probe test fixtures etc.

To this:

1.2mm pitch FCI Zipline and Amphenol Crossbow – which are certainly not easy to spring probe test if you want a fixture which works reliably day-in day-out.
1.2mm pitch FCI Zipline and Amphenol Crossbow – which are certainly not easy to spring probe test
if you want a fixture which works reliably day-in day-out.

To:

Many connectors which simply can’t be spring probe tested are now getting onto backplanes
Many connectors which simply can’t be spring probe tested are now getting onto backplanes:

The result of these changes is that no one test system can now find all the fault types.

Obviously no CEM can afford to use many pieces of different test equipment to find every single example of every type of fault if some only occur extremely infrequently. The trick is to have maximum fault coverage (taking particular fault occurrence frequencies into account) with the minimum equipment investment.

A low voltage dc electrical bed-of-nails test system will find all simple shorts and opens on a backplane containing only connectors. It may or may not be able to deal with any analogue or digital components fitted on it.

It won’t find:  “near shorts” where two conductors have become too close together but aren’t actually touching – This requires High Voltage in the 500 – 1500V range.

It won’t find: bent contact pins, many rotated connectors and components, missing or incorrect coding keys etc  - This requires automatic optical inspection - AOI

It won’t find: bent under or crushed compliant pins, soldering defects or pin-point shorts under smd connectors in a buss structure – This requires X-ray

It won’t find: Incorrect back drilling of via holes or some other obscure compliant pin defects – This requires Signal Integrity testing (TDR, TDT, S-parameter etc).

This is fault spectrum summarized in the following chart:(click to enlarge)

Test systems, fixturing, test programs and support to cover all the above fault types are available exclusively from RoBAT