module 09 shorts & pins

Agilent 3070 User Fundamentals

Pins & Shorts 9 - 1

Module 9: Shorts & Pins TestsTable of Contents

The Test Development Process .......................................................................................... 2

Shorts Test Code ................................................................................................................ 4Shorts Test - Overview....................................................................................................... 5Test Expected Shorts .......................................................................................................... 6

Shorts Test.......................................................................................................................... 8Detection and Isolation of an Unexpected Short ................................................................ 9

Detection Phase ..................................................................................................... 9Isolation Phase..................................................................................................... 10

Shorts Test Software Features .......................................................................................... 11Threshold............................................................................................................. 11Settling Delay...................................................................................................... 12Custom Failure Message ..................................................................................... 12Controlling the Report......................................................................................... 13

Shorts Test Quiz ............................................................................................................... 14Solution: .............................................................................................................. 15

Pins Test ........................................................................................................................... 16Syntax associated with Pins Test...................................................................................... 18

Syntax in the "testplan" ....................................................................................... 18Using Pins and Shorts to Verify a new fixture ................................................................. 20

test "shorts" ......................................................................................................... 20test "pins" ............................................................................................................ 21Power the board up.............................................................................................. 21

Agilent Technologies

Pins & Shorts 9 - 2

The Test Development Process• In the previous labs:

− You created the directory and the "config" file.− Translated the CAD data using CAMCAD− Finished the board description using Board Consultant, the Part

Description Editor and the Digital Setup Editor.− Generated and evaluated the "testability.rpt"− Run Test Consultant− Verified the test fixture.

• Having built the fixture, you are ready to begin turning on the individual teststhat comprise the overall 3070-test suite.

− In this module, you will learn about the Pins and Shorts Tests.− To do this, you will visit the "pins" and "shorts" files and "testplan." The

testplan manages the test sequence and monitors test status.− During the next module, you will see Agilent's PushButton Debug

interface and learn to use it when testing Pins and Shorts.− During the next module, you will perform the turn-on and debug tasks

for the Pins and Shorts tests.

13070 User FundamentalsModule 9: Shorts & Pins Test sA

Test Development FlowchartProcess Files Tools

Generates Modify

board

testability.rpt

Fixture Files

IndividualTest Files

config

testplan

Translate CAD1

Generate Test & Fixture files3

Build & Verify test Fixture4

Turn-On / Debug all Tests5

Release to Production & Long Term Support

6

Describe board & system2

Custom libraries

board_xy

ECO

CAMCAD Translator

BT-BASIC

Board Consultant

Part Description Editor

Digital Setup Editor

IPG Test Consultant

PushButton Debug


Pins & Shorts 9 - 3

• Test Consultant models the board description provided in Board Consultantand form this determines:

− Where to expect shorts− At what level to set the shorts test threshold− How long to allow for reactive components to settle after initially being

connected into the test circuit− Determines the order for testing the nodes to minimize "phantom shorts".


Pins & Shorts 9 - 4

Shorts Test Code

The "testplan" executes the shorts test by calling the subroutine "Shorts".The statement test "shorts" within the Shorts routine is what actually executes theshorts test.

• Question: Why would anyone use a subroutine to execute a single statement?Why not simply execute the test “shorts” statement?

− It conforms to other test structures.− It allows you to have more than one shorts test. You could write your

own shorts test that might test just a dip switch on your board. If theswitches are not positioned correctly, instead of failing the test, promptthe operator to reset the switches and test again.

The file “shorts” consists of some overhead (explained later).A list of expected shorts using the format:

short “<node name>” to “<node name>”

Following the expected shorts is a list of nodes that should not be shorted to any othernode. The format here is just a list:

nodes “<node name>”

− Nodes are tested in the order listed.The algorithm will be explained along with the hardware.


Shorts TestCalled from testplan

In testplan:

sub Test_Sections. . .Status = Failed_In_Shortscall Shortsif boardfailed then subexit. . .

sub Shorts test “shorts”subend


Pins & Shorts 9 - 5

Shorts Test - Overview

There are three sections to the shorts test.

• The first part of the test expects shorts.− Jumpers− Closed switches− Fuses− Small value resistors− Etc.

• The second part of the shorts test detects and isolates high impedance,unexpected shorts.

− High impedance nodes− Digital pins− Resistors above 10k

• The third section detects and isolates low impedance unexpected shorts.− Low impedance nodes− Power nodes− Resistors below 10k.


Shorts Test

! IPG: rev B.03.60 <date>threshold 12settling delay 50.00usettling delay 525.0ushort “L201-1” to “L201-2”settling delay 50.00ushort “J201-1” to “J201-2”. . .threshold 1000. . .nodes “Data7”nodes “R201-2”nodes “R201-1”

. . .threshold 8. . .nodes “R202-2”nodes “R202-1”nodes “GND”

DVM

L201Series Resistance = 6ohms

R202 at 33ohms

DVM

R201 at 20k

L201-1 L201-2

R20

1-1

R20

1-2

R20

2-1

R20

2-2


Pins & Shorts 9 - 6

Test Expected Shorts

The expected shorts test is done to detect "unexpected opens".

• Specify a test threshold: threshold 12This example sets the shorts/open threshold at 12ohms.

• Define a settling delay: settling delay 525.0uThis example sets a settling delay of 50us then immediately changes it to525us. Why? The default is 50us and that value is included in the file'soriginal source which Test Consultant uses. But, in this example, the firstnode pair tested is associated with an inductor, which has a reactance. Thesoftware calculates the time required for the signal to stabilize and adds thatinstruction to the file.

• Test:− Node "L201-1" is connected to a 100mv source.− The second node, "L201-2", is connected to ground.− A 100mV source is connected to a 100ohm resistor on the ASRU card.− A Digital Voltmeter samples the voltage drop across the 100ohm

resistor. The measured value is used to calculate the resistance betweenthe nodes.

• If the calculated resistance is above the specified threshold, the test fails.• If the calculated resistance is below the threshold, the test passes.• The next expected short is tested.


Shorts TestExpected Shorts

! IPG: rev B.03.60 <date>threshold 12settling delay 50.00usettling delay 525.0ushort “L201-1” to “L201-2”settling delay 50.00ushort “J201-1” to “J201-2”...

L201

100ohm

DVM

0.1V

L201-1 L201-2


Pins & Shorts 9 - 7

The software specifies that this is an expected short by using the syntax:

short "L201-1" to "L201-2"

The Expected Shorts portion of the Shorts test confirms that this "expected short" exist.When testing for "unexpected shorts", these nodes will be included again. The expectedshorted nodes will be tested for shorts to other nodes on the board.

The 100mv source and 100ohm resistor are not adjustable.

REMEMBER about Opens Testing:

• Tests for UNEXPECTED OPENS• Expects to find: Shorts• Fails if measured value is: Above specified threshold• Uses the statement: short “node_name” to “node_name”

• Nodes with expected shorted are tested to be shorted.• Later, these same nodes will be tested for unexpected shorts to other nodes.• Test Consultant will set the test threshold based on devices on the board.

Generally, nodes greater than 10ohms are not tested as shorted nodes.• The nodes specified as expected shorts will not be detected as a short

regardless of the threshold setting in the expected shorts section.


Pins & Shorts 9 - 8

Shorts Test

Having verified the expected shorts, the test now looks for unexpected shorts.

• Test Consultant specified a test threshold: threshold 1000• Test sequence:

− The first node, "A", is connected to the 100mv, 100ohm source.− All the remaining nodes are connected to ground.− Nodes "B" through "G" are greater than 1k from node "A".− After node "A" is tested, it is released (not re-connected to ground).− Node "B" is then disconnected from ground and sourced.− Node "B" measures greater than 1k to ground and it too is released.− Then the next node is moved from the ground connection to the source

and the test continues until all nodes have been tested.

The syntax for nodes that should not be shorted is shown for unexpected shorts.

....threshold 1000nodes "A"nodes "B"nodes "C"nodes "D"nodes "E"nodes "F"nodes "G"....


Shorts Test (Good Board)Testing For Shorts (Expecting Opens)

100mV100 Ω

“A” “B” “C” “D” “E” “F” “G”

“Node_Names”


Pins & Shorts 9 - 9

Detection and Isolation of an Unexpected Short

The shorts test is actually divided into two phases.

• Detection Phase. Here the presence of a short is determined.• Isolation Phase: The hardware sorts through the nodes until it isolates the

nodes that are shorted together. This process is referred to as half splitting.

Detection Phase

Using the example above:

− The first node "A" is tested. The remaining nodes are shorted to ground.− The 100mV signal is applied; the resistance through the resistor causes

the voltage drop at the Voltmeter to register much less than 100mV.− This node passes the shorts test.− Node "A" is released and not reconnected to ground.− Node "B" is connected to the 100mV source.− The voltage drop is measured again.− The test proceeds without failure until node "C" is sourced− Node, "C" has an unexpected short to one of the grounded nodes.− The 100mV signal is applied; the minimal resistance through the short

means the DVM measures almost the full 100mV dropped. This value istranslated to a resistance that is below the shorts test threshold of1000ohms. The node has been identified as shorted.

− This is the detection phase.


Shorts Test Detection(Bad Board)Testing For Shorts (Expecting Opens)

100mV100 Ω

“A” “B” “C” “D” “E” “F” “G”

?

Which node is shorted to node C? A short has been detected from node C to one of the remaining nodes D, E, F or G


Pins & Shorts 9 - 10

Isolation Phase− Node "C" is shorted to one of the remaining nodes.

Which one? This will be determined by the isolation phase.− The software releases half of the tested nodes from ground.− The DVM measurement is taken again.− The software releases the first half and grounds the other half.− The DVM measurement is taken again.− This half-splitting process continues until the individual node, "G" is the

only one still exhibiting the short.− This is the isolation phase.− threshold, settling delay, BRC, resistance and node names are reported.− This report can be enhanced with report options, explained next.

Short #1 Thresh 1000, Delay 500us ohmsFrom: A 22158 2To: G 21756 2

− The shorted nodes are released and testing continues.

REMEMBER: Shorts Testing

• Testing for: UNEXPECTED SHORTS• Expects to find: Opens• Fails if value is: Below the threshold• Uses the syntax: nodes "node_name"


Shorts Test Isolation(Bad Board)Testing For Shorts (Expecting Opens)

100mV100 Ω

“A” “B” “C” “D” “E” “F” “G”

?

Which node is shorted to node C? A short has been detected from node C to one of the remaining nodes D, E, F or G

Node C is not shorted to nodes D and ENode C is shorted to either nodes F or GNode C may be shorted to node GThis is not assumed!

Node C is shorted to node G



Shorts Test Software Features

Threshold

The test threshold can be varied with the threshold statement at any time during theopens or shorts test. The specified threshold remains in effect until changed by asubsequent threshold statement. Test Consultant calculates a default thresholdvalue.

threshold 16

This specifies that the threshold for the tests that follow will be 16ohm. Anything above16ohm is considered an open, anything below 16ohm, a short.It should be noted that the accuracy of the shorts test hardware is specified as:

• Range: 2 to 1000ohm• Resolution: 1ohm• Accuracy: ±(0.25% + 2ohm)


Shorts Test Software Featuresreport limit 10report netlist, common devices ! Phantoms eliminatedthreshold 16 ! 12 Jumper_1 is a mechanical jumpersettling delay 50.00ufailure “Check Jumper_1, it should be closed.”short “Jumper_1-1” to “Jumper_1-2”failure “”. . .threshold 1000. . .nodes “Data_0”nodes “Data_1”settling delay 525.0unodes “Large_Cap”settling delay 50.00u. . .threshold 8nodes “VCC”nodes “GND”nodes “Enable_Bus” ! U56 has internal 750 ohm pullup. . .



Settling Delay

Test time can be extended to allow reactive components to stabilize. Using thesettling delay statement a test will be run until the measurement passes or thespecified time elapses. The delay remains in effect until changed by a subsequentsettling delay statement. Test Consultant calculates the correct settling delay timewhen it generates the test.

settling delay 500m

This specifies that the settling delay is at 500ms. For all subsequent nodes, the 100mVsignal is applied and the measurement taken immediately. If it does not pass, continuemeasuring the DVM until the threshold is reached or until the 500ms lapses. If thethreshold is achieved, then the node passes. If not, and the 500ms elapses, the node fails.

It should be noted that the accuracy of the shorts test hardware is specified as:

• Range: 0 to 3.2768 seconds• Resolution: 50us• Default: 50us

Custom Failure Message

Often, you will want to tell the test or repair operator something about the failure. Forthat reason, you have the command failure "<message>".

• You can change the failure message at any point in the shorts test file.• You must close the message after testing nodes that relate to the message.

You close the failure message by including the failure "" command.• E.g.:

failure "Double check SW4, all rockers open!"nodes "SW4-1"nodes "SW4-2"…nodes "SW4-16"failure ""nodes "R1-1"

− If SW4-2 is shorted, the software will include the custom failure messagewith the default failure print out. The operator would see that the switchwas not set correctly, reset the switch and rerun the board.

− If failure "" is not included and node R1-1 fails; the SW4 messagewould be included in the failure message for R1. This would probably bemisleading, so be sure to always close or change the failure message.

− You can add as many failure statements as you feel necessary.



Controlling the Report

Use the report statement to define how your repair ticket will look.

• report netlistIncludes common nodes associated with devices that are shorted together.

• report common devicesIncludes all devices common to those shorted together.

• report limit <#> Limits the number of devices or nodes listed.• report phantoms

This report option will be described later in the class. Basically, it identifiesnodes that appeared to be shorted during the detection phase, but failed tofind a short during the isolation phase.

• Examples:− If "D3" is shorted to "D4" and report phantoms (default), you will get the

threshold and settling delay values. The repair ticket will only list, nodenames, BRC's and the resistance value..

− If "D3" is shorted to "D4" and report common devices is enabled, youwill get a listing of all the common devices..

− If "D3" is shorted to "D4" and report netlist, common devices is enabled,you will get a listing of all the devices and the pins that are connected tothe short. Frequently, that helps the repair operator find the fault faster.

− Report limit 10 truncates alpha-numerically the list of device pins at 10.Capacitor pins will be reported before the (U1.1) IC pins.


Shorts Test - Report Options

report common devicesreport limit 12

Short #1From: D3 22044To: D4 21938Common Devices: U1 U4

report netlist, common devicesreport limit 12

Short #1From: D3 22044 u1.5 u4.3 u5.2 u7.5To: D4 21938 u1.8 u4.4 u6.2 u2.10Common Devices: u1 u4

report phantoms

Short #1From: D3 22044To: D4 21938



Shorts Test Quiz

Given:

• An integrated circuit has an internal 750ohm resistance between nodes"Enable" and "Vcc".

• The presence of this resistance is not known by Board Consultant.• Test Consultant generates the following test code:

. . .threshold 1000nodes "Others"nodes "Enable". . .threshold 8. . .nodes "VCC"

• What will happen when this device is tested?− Shorts #1 752 Ohms

From: Enable 22158To: VCC 21756

• How can you correct this problem?


Shorts TestShorts Quiz

. . .threshold 1000nodes "others"nodes "Enable". . . threshold 8. . .nodes "VCC"

750ohm

Vcc

Enable



Solution:• The nodes "Enable" and "VCC" will be detected as shorts because the

750ohm resistance is less than the 1000ohm threshold.• Move node "Enable" to below the 8ohm threshold.

• The "best practice solution" is to return to Board Consultant and enter the750ohm resistance in the integrated circuit with the Part description Editor.

− Enter a resistor, mark it No Test, set the thresholds very wide.If all the parts used do not include an internal pullup.

− Rerun Test Consultant.Test Consultant will not write a test for the resistor but it will recognizethe impedance path from Enable to VCC and arrange the nodes properly.

− Or− Enter a resistor, mark it No Test, set the thresholds very wide.

If all the parts used do include an internal pullup.− Rerun Test Consultant.

Test Consultant will write a test for the resistor and it will recognize theimpedance path from Enable to VCC and arrange the nodes properly.



Pins Test

The Pins test identifies fixture contact problems.

The Pins Test process:

• Connects all the nodes (except one) to ground• Apply a signal on the one ungrounded node.• If there is current flow then the probe must be making contact to the printed

circuit board.• If there is no current flow, then the probe is not making contact and the Pins

test fails.• Having tested a node, that node is reconnected to ground and the next node is

moved from the ground connection to the source and testing continues.

Pins Test is different from shorts:

• The voltage applied is increased from 100mv to 2.5 volts. This ensures that adiode or transistor will turn on and conduct the signal to ground. It alsoassumes that an integrated circuit will have leakage at this voltage and thatwill establish a current flow.

• The current limiting resistor is also increased in value, from 100ohm to 10Kfor the pins test.


Pins Test

+2.5V10K

“A” “B” “C” “D” “E” “F” “G”

“Node_Names”



The goal is to test for proper fixture contact by detecting a current flow; even a verysmall leakage current will serve the purpose. It is expected that there will be a currentflow from the source, onto the PC board and back to ground (remember, except for theone node connected to the source, all other nodes are connected to ground).

Special considerations:

• What about the node on the cathode of the two diodes in the above example?Here the two diodes are back-biased. The 2.5v signal will not be propagatedto any other node. Therefore, this node must be isolated. Not really, when thesoftware detects a situation like this, the polarity is reversed (automatically)and the 2.5v signal becomes -2.5v. Now there is ample current flow and thenode is no longer isolated.

• However, one node type is isolated and cannot be tested by Pins Test. A nodeisolated by capacitors cannot propagate either the positive or negative 2.5vsignal to another node. The node between the two capacitors is such a node.

• When Test Consultant generates the Pins Test file, it analyzes the topologyand comments out nodes that should be isolated.

• As part of the test turn on process, you should review the “pins” file andconfirm that commented nodes really are isolated. You should also executethe test to confirm that none of those nodes being tested are isolated.

When to run Pins Test:

• One theory has you run the Pins test immediately after the vacuum is applied,before running any tests. If there is poor contact, the software allows theoperator to cycle the vacuum (faoff/faon). This can often correct the fixturecontact. As an example, if the problem is due to a dirty PC board, cycling thevacuum may pierce the contaminant. When the contact has been confirmedto be good, testing can begin.

• The second theory runs the testplan. If there are failures, execute the PinsTest. The motivating factor here: Why run the Pins test on a good board?Instead, only run Pins test when a failure has been detected. This is thedefault mode.



Syntax associated with Pins Test

The pins test software contains a list of the nodes on the board. Each is prefaced by thekeyword “nodes”.The test generator writes the test automatically.The nodes are tested in the order presented.

Syntax in the "testplan"

The Pins Test is controlled by setting a flag in the “Set_Custom_Options” subroutine.

• Find the Chek_Point_Mode flag in Set_Custom_Options routine. It can beset to OFF, PRETEST or FAILURES. (e.g.: Chek_Point_Mode = Pretest)

− OFF - Do not use Pins Test at all.− PRETEST - Run the Pins Test on every board, as the first test.− FAILURES - Run the Pins Test only after a failure has been detected.

The actual command that executes the Pins Test is "fnPinsfailed.” This function isexecuted or skipped depending on the status of the Chek_Point_Mode flag.


Pins Test - Syntax

nodes "A"nodes "B"nodes "C"nodes "D"!nodes "E” ! node capacitively isolatednodes ”F"nodes ”G"



Why is Chek_Point/Pins Test managed like this instead of like any other test?

• This is a unique test in that it is testing the board - fixture contact, not partson the board.

• It is an optional test.• Because different manufacturing models exist, different users will find this

test either invaluable or a waste of time.− For those users who are having difficulty with “no-clean” production,

running Chek_Point before executing a test will allow the operator toensure good contact is made.

− For users with occasional contact problems, running Chek_Point beforethe test might be unnecessary, but running Chek_Point after a failuremight catch those intermittent contact problems.

− For any user, running Chek_Point only when a failure is found meansthat the repair loop will only see faulty boards, not bad contact boards.But for some users, the added test time of Chek_Point and operatorinteraction means an unnecessary burden on throughput. For these users,omitting this test can result in more boards being tested per hour or day.

Pins Test and Chek_Point refer to exactly the same test. Why have two names?

• Initially Chek_Point was to refer to the PRETEST mode while Pins Testreferred to the FAILURES test mode. But that was discarded whenprogrammers realized they were really the same test. Unfortunately, the twonames survived the redesign.



Using Pins and Shorts to Verify a new fixture

After the fixture is built, the fixture wiring must be verified.

• Use the verify commands reviewed earlier to verify the fixture.• Having completed that verification process, continue with the following tests

to dispel all fixture-wiring doubts.

test "shorts"

Run the shorts test with a blank board on the fixture.

• Expected shorts should fail, if they do not, then look for a wiring error thatshorts together the expected shorts.

• If there are shorted nodes, these are fixture wiring errors.

Run the shorts test with no PC board at all.

• This is an extension of the blank board and points to wires in the wrong placewithin the fixture.

Run the shorts test with a known good (loaded) board on the fixture.

• There should be no failures.• If all nodes appear to be shorted, check the inter-module wiring for GOUT

and LOUT. If these wires are omitted or miswired, the nodes in one moduleappear to be shorted to the nodes in other modules. Thus, a very long list ofshorts test failures is issued.


Use Pins & Shorts to Verify Fixtures

Test Shorts• With No board on the fixture• With a board on the fixture

Test Pins• With a “shorting plate”• With the board on the fixture

Turn on the Power Supplies• Test current draw from power supply

Verify All Nodes• Use a blank printed circuit board

Manually verify Power Supply wiring• Verify connections to Control Card and ASRU



test "pins"

Get a copper clad board, prior to etching, that has the proper tooling holes drilled or makeyour own by wrapping your blank board with a coating of aluminum foil.Create a custom “pins” test as follows:

• Copy “pins” to “copper_clad_pins”• Remove any commented nodes, re-save and compile.

• Because the copper clad board should short all nodes together, the resultshould be that all nodes pass the Pins test; none are isolated, none are open.

• Run this test with the copper clad board when you suspect a fault with thefixture.

− If it fails, you have identified an open circuit in the fixture.− If it passes, then the fault is not an open in the fixture.

Power the board up

The fixture verification software does not reach the ASRU or Control Cards. They mustbe verified manually.

With a blank board on the fixture, turning the power supplies on and check that the“Vcc”, “+12V” and other power nodes do power up to the correct voltage and do notcurrent limit.

• If the power-on sequence fails, you know there is a fixture wiring error.• Look at the front panel of the power supply or ask the supply how much

current is required1. The current value should be very low.• Check the DC voltage level (look at the front panel or poll each supply).

− The voltage should be stable (not fluctuating).− If the supply is not maintaining a constant voltage, then its sense wire is

miswired. The supply is fluctuating because it senses that the voltage isnot correct (because the sense wire is not on the correct node). Thevoltage and current are increased slightly. This shows no reaction in thesense lead, so the supply reduces its output. This cycle continues until thesense wire is connected correctly.

• If the power seems steady with a blank board, try with the loaded board too.

Clearly, the power should not be applied until all miswires have been corrected.

1 The BT-Basic command rps <#> will report the specified power supply voltage and current

outputs. Rps2 reports power supply 2's voltage and current.

module 09 shorts & pins

Documents

copper clad

00u short

0u short l201

part description

test consultant

rerun test

test consultant

shorts test