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From: Enrico on 19 Feb 2010 14:26
Hi,

I need to build an in-circuit board tester.

Basically I need to measure:

1) resistors (2 Ohm to 1 MOhm)
2) capacitors (10 nF to1000 uF)
3) inductors (10 uH to 10 mH)
4) diodes polarity
5) transistors base-emitter polarity

I don't need to do "Open Pin Scan".

I'm thinking to use the following chip from Analog: AD5520

The bed-of-nails and the contacting system is ready.

Any help or hint will be appreciated

Enrico
From: Paul Carpenter on 19 Feb 2010 19:58
In article <c3f94d04-697b-47b0-aa7e-
c1795f56aabe(a)q21g2000yqm.googlegroups.com>, zigbee(a)libero.it says...
> Hi,
>
> I need to build an in-circuit board tester.

Production, development, or for batch qauality full audit.

Circuit powered or unpowered?

Circuit idle or in use?

For
how many points (impetus/response) at same time
total number of test points
total number of tests per point

How often does the unit have to be calibrated and to what
standards?

You do have a full test spec to work to for all the tests?
Including lower and upper limits?

> Basically I need to measure:
>
> 1) resistors (2 Ohm to 1 MOhm)

How many and how many different ranges?

You do know what the circuit loading variations are going to
be at all points.

You do know how to calculate on the fly the new upper/lower
limits if measuring at a point where one resistors variance
could affect another reading.

No in circuit capacitance to allow for measurement settling time.

What response time.

> 2) capacitors (10 nF to1000 uF)

That is a wide range to test, and requires some form of
loading circuit, to get approximate idea as the rest of
the circuit capacitance will also be measured.

Load may affect circuit.

Over what frequency range.

What response time.

> 3) inductors (10 uH to 10 mH)

Same as per capacitors

> 4) diodes polarity

Why?

Run diode test on some types of very small signal diode
especially reverse voltage can blow them. This means you
will have to have programmeable drive and range selection.

> 5) transistors base-emitter polarity

Again why, and this is only a diode test.

> I don't need to do "Open Pin Scan".

This is always useful to check your probes are connected properly
and right orientation to the circuit. Garbage In Garbage Out.

> I'm thinking to use the following chip from Analog: AD5520

That is meant for parameteric testing of semiconductors with 64 pin
LQFP per active impetus and response pin of test. I.E. to check under
test conditions a batch of devices function within all limits, over
the full temperature range of the device.

Even semiconductors undergo functional test only for production as
full parametric testing takes too long, when you have a 10 inch wafer
with 50,000+ parts on it. Non military/avionic usually at room
temperature only.

Unless you are designing for space applications where 100% test is
required, this seems overkill.

> The bed-of-nails and the contacting system is ready.

I assume with a huge bank of relays to configure which sets of pins
are going to be active at any point in time, for each test. Otherwise
you will need a 64 pin LQFP for EACH 'nail', which makes test setup
and changeover lengthy and have to be done in particular sequence
to avoid circuit damage. Controlling that will be a nightmare.

How many 'nails' do you have as this seems overkill fo a circuit
test.

No doubt you will have to run open-pin scans to check that each
test is configured properly and a relay has not stuck/failed.

Also as you will have to have banks of relays for matrix switching
(to ensure connection path impedance does not effect measurements)
this means lots of cabling and connections, which means more points of
failure.

It takes ages to setup and test/calibrate a tester like that.

> Any help or hint will be appreciated

I have designed and commissioned ASIC testing systems for wafer probing
to full packaged parts, connecting to units being tested on full
military/avionics temperature range. These are for production and still
only do functional testing at limit points.

What you are describing seems overkill.

The control, vectors and pass/fail limits for this are going to be
massive, and with measuring capacitance and inductance, will extend
testing time to make this unprofitable for any size circuit. The larger
the board the more tests are required.

> Enrico
>

--
Paul Carpenter | paul(a)pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/> PC Services
<http://www.pcserviceselectronics.co.uk/fonts/> Timing Diagram Font
<http://www.gnuh8.org.uk/> GNU H8 - compiler & Renesas H8/H8S/H8 Tiny
<http://www.badweb.org.uk/> For those web sites you hate
From: Enrico on 21 Feb 2010 13:51
Hi Paul,

thanks for your answer.

PREFACE
---------------
Our boards usually have: one microcontroller, passive components, one
DC/DC converter, some analog, leds, push buttons, and relays.

Our boards' power supply is +24 Volt DC.

We are a small company. We do the actual design, we route the board,
and we write the software for the microcontroller.

We are just approaching the world of Tests and Measurements.

So far, I've been doing just Functional Tests. But I would like to do
both: in-circuit test and functional test

We also make the contacting system and the bed-of-nail (we use a piece
of PCB as a substrate)

What I would like to make is a lab-made in-circuit tester to test our
products.

What I know is:

1) In circuit tests are carried out with the board NOT POWERED
2) Accoding to Teradyne's standards, signals used during in-circut
tests are in the +/-200 mV range, in order not to power up the board

I've been looking around for almost a year for a cheap In-circuit Test
but couldn't find anything I can afford. Here are some prices:

Spea 3030 = 30.000 to 35.000 Euros
Keithley 2600 Source Meter + Analog Mux + Relay matrix = 20.000 Euros
German Company (*) = 25.000 Euros (*) I can't remember the name

I actually need to build an instruments like the "smart tweezers":
http://www.smarttweezers.com/?gclid=CK6Uy6eHhKACFUWU3wodeEOrsw

This instruments cost 315.00 $


ANSWERS
----------------
> Production, development, or for batch qauality full audit.
Production. My volumes are 1000 to 5000 boards at a time.

> Circuit powered or unpowered?
Unpowered

> Circuit idle or in use?
Unpowered

> For
>    how many points (impetus/response) at same time
>    total number of test points
>    total number of tests per point
30 to 50 test points.


> How often does the unit have to be calibrated and to what
> standards?
Once a year.

> You do have a full test spec to work to for all the tests?
> Including lower and upper limits?

I just need to know the value of Resistors, Capacitors, Inductors and
the diodes' polarity.
I don't want to do full parametric or margin tests.


> > Basically I need to measure:
>
> > 1) resistors (2 Ohm to 1 MOhm)
>
> How many and how many different ranges?
The total number of resistors are 10 to 20. Different ranges are 5 to
10

> You do know what the circuit loading variations are going to
> be at all points.
I don't understand the question. Maybe because I don't have
experiences in tests.

> You do know how to calculate on the fly the new upper/lower
> limits if measuring at a point where one resistors variance
> could affect another reading.
I don't understand the question. Maybe because I don't have
experiences in tests.

> No in circuit capacitance to allow for measurement settling time.
>
> What response time.
I don't understand the question. Maybe because I don't have
experiences in tests.

> > 4) diodes polarity
> Why?
I need to know if the diode is correctly oriented.


> > I don't need to do "Open Pin Scan".
>
> This is always useful to check your probes are connected properly
> and right orientation to the circuit. Garbage In Garbage Out.
Open Pin Tools costs 5000 to 10000 Euro
My production volumes are not big (1000 to 5000) therefore I can't
afford one.

> > I'm thinking to use the following chip from Analog: AD5520
>
> That is meant for parameteric testing of semiconductors with 64 pin
> LQFP per active impetus and response pin of test. I.E. to check under
> test conditions a batch of devices function within all limits, over
> the full temperature range of the device.
>
> Even semiconductors undergo functional test only for production as
> full parametric testing takes too long, when you have a 10 inch wafer
> with 50,000+ parts on it. Non military/avionic usually at room
> temperature only.
>
> Unless you are designing for space applications where 100% test is
> required, this seems overkill.


> > The bed-of-nails and the contacting system is ready.
>
> I assume with a huge bank of relays to configure which sets of pins
> are going to be active at any point in time, for each test. Otherwise
> you will need a 64 pin LQFP for EACH 'nail', which makes test setup
> and changeover lengthy and have to be done in particular sequence
> to avoid circuit damage. Controlling that will be a nightmare.

The bank of relays is not that huge: 1 Eurocard = 128 relays

> How many 'nails' do you have as this seems overkill fo a circuit test.
30 to 50 nails


> Also as you will have to have banks of relays for matrix switching
> (to ensure connection path impedance does not effect measurements)
> this means lots of cabling and connections, which means more points of
> failure.

The system I got in mind is:

1 board (Euro card size) with 128 small signal RELAYS
1 board (Euro card size) with MICROCONTROLLER + ADC + AD5520

The MICROCONTROLLER does the measurements and sends to the PC the
results.

The challenge is to optically isolate the sytem from the PC.

OPEN PROBLEMS
----------------------------
I don't know how to measure capacitors and inductors
I don't know how to guard a node of a circuit?

The measurements methods are a secret, I couldn't find a single book
about in-circuit tests.


QUESTION
----------------
Is the AD5520 suitable to build a system like that?



Enrico
From: Paul Carpenter on 21 Feb 2010 17:51
In article <4b6f2755-b613-4085-b1e5-
c61554e79220(a)e1g2000yqh.googlegroups.com>, zigbee(a)libero.it says...
> Hi Paul,
>
> thanks for your answer.
>
> PREFACE
> ---------------
> Our boards usually have: one microcontroller, passive components, one
> DC/DC converter, some analog, leds, push buttons, and relays.

So you are likely to need

a) different bed of nails for each product variation
b) probably different relay matrix board for each product variation

> Our boards' power supply is +24 Volt DC.
>
> We are a small company. We do the actual design, we route the board,
> and we write the software for the microcontroller.

Like a lot of companies.

> We are just approaching the world of Tests and Measurements.
>
> So far, I've been doing just Functional Tests. But I would like to do
> both: in-circuit test and functional test

What are you trying to acheive beyond your existing tests?

> We also make the contacting system and the bed-of-nail (we use a piece
> of PCB as a substrate)
>
> What I would like to make is a lab-made in-circuit tester to test our
> products.

You have not said why you need this level of test and what you are
trying to achieve beyond functional test.

> What I know is:
>
> 1) In circuit tests are carried out with the board NOT POWERED
> 2) Accoding to Teradyne's standards, signals used during in-circut
> tests are in the +/-200 mV range, in order not to power up the board

That spec is mainly for semiconductor testing, in your cicruit, you
may or may not be able to use higher voltages.

Which also means you need to keep cable lengths SHORT, and path
resistance (cables, relays, nail connection and measurement circuit)
to minimum to avoid affecting the measurements.

Especially for low resistance (<100R).

Similarly avoiding interference for capacitance and inductance tests.

> I've been looking around for almost a year for a cheap In-circuit Test
> but couldn't find anything I can afford. Here are some prices:
>
> Spea 3030 = 30.000 to 35.000 Euros
> Keithley 2600 Source Meter + Analog Mux + Relay matrix = 20.000 Euros
> German Company (*) = 25.000 Euros (*) I can't remember the name
>
> I actually need to build an instruments like the "smart tweezers":
> http://www.smarttweezers.com/?gclid=CK6Uy6eHhKACFUWU3wodeEOrsw
>
> This instruments cost 315.00 $

Search Circuit Cellar for a LC meter using tweezers for surface mount
components. There was an article in December 2008 issue - 'Component
control' that did just this.

> ANSWERS
> ----------------
> > Production, development, or for batch qauality full audit.
> Production. My volumes are 1000 to 5000 boards at a time.

How much time do you expect the tests to take per board?

You would have to a high failure rate due to component assembly
problems to justify this. Maybe you are fixing the wrong problem.

> > Circuit powered or unpowered?
> Unpowered
>
> > Circuit idle or in use?
> Unpowered
>
> > For
> >    how many points (impetus/response) at same time
> >    total number of test points
> >    total number of tests per point
> 30 to 50 test points.

Work out what you think for one board the FULL list of
TESTS and expected results, then try doing the tests using
a multimeter and get a GUIDE time for each test.

This will compare with the relay turn off delay and next relay
turn on time, impetus setup and settling time, and measurement
sampling time.

> > How often does the unit have to be calibrated and to what
> > standards?
> Once a year.

How are you going to calibrate the unit?
You will need to calibrate bearing in mind the cabling, relays
etc..

> > You do have a full test spec to work to for all the tests?
> > Including lower and upper limits?
>
> I just need to know the value of Resistors, Capacitors, Inductors and
> the diodes' polarity.

Resistors, capacitors and inductors have tolerances, and combined
in a circuit they will have a combined tolerance, so you will have
an upper and lower limit for EACH measurement.

> I don't want to do full parametric or margin tests.

There will always be some form of margins for the test.

> > > Basically I need to measure:
> >
> > > 1) resistors (2 Ohm to 1 MOhm)
> >
> > How many and how many different ranges?
> The total number of resistors are 10 to 20. Different ranges are 5 to
> 10

That is a complex range switching for max 200mV, along with switching out
for other types of tests.

> > You do know what the circuit loading variations are going to
> > be at all points.
> I don't understand the question. Maybe because I don't have
> experiences in tests.

Maybe basic circuit theory, there WILL be other impedances in
parallel with what you are testing, so you need to know the
variations of all parts loading the point of test.

> > You do know how to calculate on the fly the new upper/lower
> > limits if measuring at a point where one resistors variance
> > could affect another reading.
> I don't understand the question. Maybe because I don't have
> experiences in tests.

If one measurement is affected by the tolerances of another component
being near one of its limits, could affect other measurements.

> > No in circuit capacitance to allow for measurement settling time.
> >
> > What response time.
> I don't understand the question. Maybe because I don't have
> experiences in tests.

Basic circuit theory, what is maximum capacitance in parallel with
an impedance test will create an RC delay with your tester so will
take a variable amount of time (due to size of C) to settle to the
level you expect to measure.

> > > 4) diodes polarity
> > Why?
> I need to know if the diode is correctly oriented.

You must have a high failure rate on board assembly to justify this.

> > > I don't need to do "Open Pin Scan".
> >
> > This is always useful to check your probes are connected properly
> > and right orientation to the circuit. Garbage In Garbage Out.
> Open Pin Tools costs 5000 to 10000 Euro
> My production volumes are not big (1000 to 5000) therefore I can't
> afford one.

Sorry you are wrong you need to sample various points to make sure your
board is orientated correctly and making correct contact, otherwise you
will get a lot of false positives (failures that are actually test
equipment malfunction).

It needs to be built into your testing procedure to interpret results
correctly, NOT a specific piece of equipment.

> > > I'm thinking to use the following chip from Analog: AD5520
> >
> > That is meant for parameteric testing of semiconductors with 64 pin
> > LQFP per active impetus and response pin of test. I.E. to check under
> > test conditions a batch of devices function within all limits, over
> > the full temperature range of the device.
> >
> > Even semiconductors undergo functional test only for production as
> > full parametric testing takes too long, when you have a 10 inch wafer
> > with 50,000+ parts on it. Non military/avionic usually at room
> > temperature only.
> >
> > Unless you are designing for space applications where 100% test is
> > required, this seems overkill.
>
>
> > > The bed-of-nails and the contacting system is ready.
> >
> > I assume with a huge bank of relays to configure which sets of pins
> > are going to be active at any point in time, for each test. Otherwise
> > you will need a 64 pin LQFP for EACH 'nail', which makes test setup
> > and changeover lengthy and have to be done in particular sequence
> > to avoid circuit damage. Controlling that will be a nightmare.
>
> The bank of relays is not that huge: 1 Eurocard = 128 relays

You are forgetting all the signal path integrity and crosstalk problems
that can occur for small signal routing.

> > How many 'nails' do you have as this seems overkill fo a circuit test.
> 30 to 50 nails
>
>
> > Also as you will have to have banks of relays for matrix switching
> > (to ensure connection path impedance does not effect measurements)
> > this means lots of cabling and connections, which means more points of
> > failure.
>
> The system I got in mind is:
>
> 1 board (Euro card size) with 128 small signal RELAYS

Needs cables to bed of nails

Bad of nails is also a potential point of failure

> 1 board (Euro card size) with MICROCONTROLLER + ADC + AD5520

Needs cable to relay board.

Needs either on board software for each product to test or means
of selecting tests, or a host (PC) programme to control the tests.

> The MICROCONTROLLER does the measurements and sends to the PC the
> results.

So you have to develop a host programme for each product test procedure
along with means of identifying the board set capabilities, product to
test. Let alone know the board is correctly orientated

> The challenge is to optically isolate the sytem from the PC.

That is the least of your worries, and I reckon for an unpowered circuit
hardly necessary. Ground loop problems maybe.

> OPEN PROBLEMS
> ----------------------------
> I don't know how to measure capacitors and inductors

Plenty of resources for correct Google search.

> I don't know how to guard a node of a circuit?

What do you mean by 'guard a node', I have a suspicion you mean
something different to everybody else.

I suspect you expect to isolate each component to measure it
as if it was a discrete component. This will not be possible
if parts are assembled on the board, without a secondary assembly
process of adding lots of links to put the components back into
circuit, which you will then have to test that all over again to
check the links are all in.

> The measurements methods are a secret, I couldn't find a single book
> about in-circuit tests.

Probably because you are looking for the wrong thing, i.e. one book
to answer all your questions.

There are plenty of resources including books, papers and other things
describing measurement methods.

> QUESTION
> ----------------
> Is the AD5520 suitable to build a system like that?

Overkill for what you are doing.

Work out how each type of measurement is made, then work out what you
need.

I personally think you need to contract someone else to design this
to meet your company requirements.

--
Paul Carpenter | paul(a)pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/> PC Services
<http://www.pcserviceselectronics.co.uk/fonts/> Timing Diagram Font
<http://www.gnuh8.org.uk/> GNU H8 - compiler & Renesas H8/H8S/H8 Tiny
<http://www.badweb.org.uk/> For those web sites you hate
From: MK on 22 Feb 2010 03:31

"Enrico" <zigbee(a)libero.it> wrote in message
news:4b6f2755-b613-4085-b1e5-c61554e79220(a)e1g2000yqh.googlegroups.com...
Hi Paul,

thanks for your answer.

PREFACE
---------------
Our boards usually have: one microcontroller, passive components, one
DC/DC converter, some analog, leds, push buttons, and relays.

Our boards' power supply is +24 Volt DC.

We are a small company. We do the actual design, we route the board,
and we write the software for the microcontroller.

We are just approaching the world of Tests and Measurements.

So far, I've been doing just Functional Tests. But I would like to do
both: in-circuit test and functional test

We also make the contacting system and the bed-of-nail (we use a piece
of PCB as a substrate)

What I would like to make is a lab-made in-circuit tester to test our
products.

What I know is:

1) In circuit tests are carried out with the board NOT POWERED
2) Accoding to Teradyne's standards, signals used during in-circut
tests are in the +/-200 mV range, in order not to power up the board

I've been looking around for almost a year for a cheap In-circuit Test
but couldn't find anything I can afford. Here are some prices:

Spea 3030 = 30.000 to 35.000 Euros
Keithley 2600 Source Meter + Analog Mux + Relay matrix = 20.000 Euros
German Company (*) = 25.000 Euros (*) I can't remember the name

I actually need to build an instruments like the "smart tweezers":
http://www.smarttweezers.com/?gclid=CK6Uy6eHhKACFUWU3wodeEOrsw

This instruments cost 315.00 $


ANSWERS
----------------
> Production, development, or for batch qauality full audit.
Production. My volumes are 1000 to 5000 boards at a time.

> Circuit powered or unpowered?
Unpowered

> Circuit idle or in use?
Unpowered

> For
> how many points (impetus/response) at same time
> total number of test points
> total number of tests per point
30 to 50 test points.


> How often does the unit have to be calibrated and to what
> standards?
Once a year.

> You do have a full test spec to work to for all the tests?
> Including lower and upper limits?

I just need to know the value of Resistors, Capacitors, Inductors and
the diodes' polarity.
I don't want to do full parametric or margin tests.


> > Basically I need to measure:
>
> > 1) resistors (2 Ohm to 1 MOhm)
>
> How many and how many different ranges?
The total number of resistors are 10 to 20. Different ranges are 5 to
10

> You do know what the circuit loading variations are going to
> be at all points.
I don't understand the question. Maybe because I don't have
experiences in tests.

> You do know how to calculate on the fly the new upper/lower
> limits if measuring at a point where one resistors variance
> could affect another reading.
I don't understand the question. Maybe because I don't have
experiences in tests.

> No in circuit capacitance to allow for measurement settling time.
>
> What response time.
I don't understand the question. Maybe because I don't have
experiences in tests.

> > 4) diodes polarity
> Why?
I need to know if the diode is correctly oriented.


> > I don't need to do "Open Pin Scan".
>
> This is always useful to check your probes are connected properly
> and right orientation to the circuit. Garbage In Garbage Out.
Open Pin Tools costs 5000 to 10000 Euro
My production volumes are not big (1000 to 5000) therefore I can't
afford one.

> > I'm thinking to use the following chip from Analog: AD5520
>
> That is meant for parameteric testing of semiconductors with 64 pin
> LQFP per active impetus and response pin of test. I.E. to check under
> test conditions a batch of devices function within all limits, over
> the full temperature range of the device.
>
> Even semiconductors undergo functional test only for production as
> full parametric testing takes too long, when you have a 10 inch wafer
> with 50,000+ parts on it. Non military/avionic usually at room
> temperature only.
>
> Unless you are designing for space applications where 100% test is
> required, this seems overkill.


> > The bed-of-nails and the contacting system is ready.
>
> I assume with a huge bank of relays to configure which sets of pins
> are going to be active at any point in time, for each test. Otherwise
> you will need a 64 pin LQFP for EACH 'nail', which makes test setup
> and changeover lengthy and have to be done in particular sequence
> to avoid circuit damage. Controlling that will be a nightmare.

The bank of relays is not that huge: 1 Eurocard = 128 relays

> How many 'nails' do you have as this seems overkill fo a circuit test.
30 to 50 nails


> Also as you will have to have banks of relays for matrix switching
> (to ensure connection path impedance does not effect measurements)
> this means lots of cabling and connections, which means more points of
> failure.

The system I got in mind is:

1 board (Euro card size) with 128 small signal RELAYS
1 board (Euro card size) with MICROCONTROLLER + ADC + AD5520

The MICROCONTROLLER does the measurements and sends to the PC the
results.

The challenge is to optically isolate the sytem from the PC.

OPEN PROBLEMS
----------------------------
I don't know how to measure capacitors and inductors
I don't know how to guard a node of a circuit?

The measurements methods are a secret, I couldn't find a single book
about in-circuit tests.


QUESTION
----------------
Is the AD5520 suitable to build a system like that?



Enrico


Hello Enrico,

I think you are looking at this the wrong way - if you need in circuit
componet test go out an buy a tester - it will cost you more to build than
to buy once you factor in the cost of development of the hardware and
software. If you buy in you get a system with all the problems sorted and
enough help/training to get it going (or your money back !!).

But do you NEED in circuit component test ?

If your board assembler uses automatic optical component checking then you
can be pretty sure that every joint is soldered and every part the same on
every board. If you have some very critical areas in your design then make
them testable by adding testpoints, on board self test, whatever.

Far better to put some work into your design than into re-inventing a test
system which you could buy.

Michael Kellett


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