Below is the Unisoft test probe access nets free calculator. Using
this calculator, you can identify nets on a PCB that do not have
satisfactory test probe access for use in, for example, a bed-of-nails
in-circuit test fixture.
The Unisoft software cross-checks that proper test probe access is
available by analyzing each electrical net trace to ensure test probe
accessibility. This analysis is typically done during the PCB's design
phase. Ensuring proper test probe access minimizes issues during the testing
phases of the manufacturing process, including functionality and quality
assurance. Supporting comprehensive electrical testing is a critical Design
For Test (DFT) consideration that facilitates In-Circuit testing (ICT),
Flying Probe, Functional testing, etc.
This calculator performs a
quick testability Design For Test (DFT) analysis for Bed Of Nails In-Circuit
type testing. It checks the nets and component pins for accessibility or
lack thereof for bottom-side test probes.
For more thorough test
fixture analysis, design, and generation of test program files for
In-Circuit, Flying Probe, and other testers, see the Unisoft software module
www.unisoft-cim.com/pcbtest.php .
What the test probe access calculator will do and
create: The software processes a Unisoft PCB file with the extension
.fba, which contains data such as component reference designators, pins, XY
coordinates, nets, device types, surface types, and other attributes. The
.fba file also includes component pins marked as no-connect (9999). The
software then analyzes this data to determine if a test probe can be
assigned to the component pins on various nets by applying basic testability
rules. The goal is to assist in the creation of an in-circuit test fixture,
such as a bed-of-nails, for testing circuit boards.
This
calculator analyzes test probe access for bottom-side test fixture designs.
For top-side test probe access or clamshell fixtures, refer to the Unisoft
software module available at
www.unisoft-cim.com/pcbtest.php.
Outputs created:
Total nets: Displays total number of nets on the PCB.
Total no-connect (9999) component pins:
This shows the total number of component pins that are not connected to any
net. Unisoft software detects these pins as existing on a device package,
but without netlist connections. These points, if left unaddressed, will not
have test probes assigned and will not be tested for shorts against other
component pins on the PCB. Example: Component U9 has 16 pins, but only
pin 11 is unconnected in the netlist. The software will create a no-connect
entry for U9 pin 11 and assign it a pseudo net number (9999). Later, using
the Unisoft Test Fixture design software, a unique net number and name can
be assigned to this pin, and a test probe can be placed if necessary.
No test
probe access nets confirmed: Lists nets and
component pins on the PCB that lack test probe access from the bottom side
of the PCB. The rules for this list are:
- No
test probe access is assigned to any Surface Mount Device (SMD) components
on the top side of the PCB, regardless of the number of pins.
-
No test probe access is assigned to any bottom-side SMDs with two or more
pins.
- No test probe access is assigned to any
Thru-Hole Devices (THD) on the bottom side.
Test probe access nets confirmed:
Lists nets and component pins on the PCB
that have test probe access from the bottom side of the PCB. The rules for
this list are:
- Test probe access
is assigned to any Thru-Hole Devices (THD) on the top side.
- Test probe access is assigned to any bottom-side SMD with only one pin.
- Test probe access is assigned to any via.
To Use the Calculator:
In the Unisoft software, export a .FBA file containing component
reference designators, pin XY coordinates, nets, device types, surfaces,
etc. The .FBA file also contains no-connect (9999) component pins. A sample
follows.
7 - BDAT-9 U10
19 X -5.875 Y 0.300 T S
7 - BDAT-9 U2 3 X -5.338 Y 1.860 T S
7 -
BDAT-9 U2 35 X -5.063 Y 2.240 T S
8 - RD1 U10 58 X -4.925 Y 0.650 T S
8 - RD1 U5 8 X -4.325 Y 1.925 T S
8 - RD1 U9 38 X -5.350 Y 1.550 T S
To export the .FBA file, click 'EXPORT CAD'. Then click 'EXPORT STANDARD
CAD FILE [.FBA]' and save the file in the desired directory.
In the box labeled 'CHOOSE FILE' below, click it to browse for the .FBA file
you wish to import. After selecting the file, click 'OPEN'.
Click 'PROCESS FILE' to display the data.
.
If you wish to save the data to a file, click the 'SAVE DATA TO
FILE' button.
The calculator above is provided for informational purposes only. Unisoft
assumes no responsibility for any issues that may arise from its use.
DFM / DFA / DFT checks the Unisoft software supports:
Design for Manufacturing / Assembly / Test (DFM / DFA / DFT) for PCB
manufacturing is a very broad and complex subject area. DFM / DFA / DFT in PCB
electronics manufacturing is a comprehensive approach aimed at designing
PCBs in a way that makes them easier and more cost-effective to manufacture.
DFM / DFA / DFT checks focus on optimizing the design of a PCB to ensure it meets
manufacturing capabilities while minimizing potential issues that could
arise during the manufacturing process. The goal is to improve the overall
efficiency of production, reduce costs, and ensure the quality of the final
product. Most aspects of DFM / DFA / DFT are addressed during the design phase of
a printed circuit board (PCB), utilizing sophisticated software and
techniques provided by various CAD systems. These systems are essential for
designing PCBs, and there are hundreds of DFM / DFA / DFT criteria that need to be
checked. When done correctly, adequate DFM / DFA / DFT measures should be in place
before the assembly and testing of the board begin. The Unisoft software,
which imports various CAD files and bills of materials (BOM) from the PCB
CAD Design Systems, can assist in verifying that DFM / DFA / DFT has been properly
applied to the PCB design in certain areas. For more details on these methods, contact Unisoft directly
or use the online help tooltips provided.
Areas where
the Unisoft software may assist in verifying that DFM / DFA / DFT was executed properly:
Component Placement
Spacing: The Unisoft software cross checks that proper spacing between
components is in place on the PCB by testing the distance between pins for
unique reference
designators. This proper spacing
between components is normally done in the design phase of the PCB. Proper spacing
between components allows for efficient assembly and to
minimize issues during
soldering processes.
Test Probe Access
Nets: The Unisoft software cross checks that proper test probe assess is
available by analyzing each electrical net trace to ensure access for test
probes. This proper test
probe assess is normally
done in the design phase of the PCB. Proper test probe access minimizes
issues during testing phases of the manufacturing process in functionality
and quality assurance.
Ensuring that the PCB design supports comprehensive electrical testing is a critical
Design For Test (DFT) consideration that facilitate In-Circuit testing
(ICT), Flying Probe, Functional testing, etc.
Assembly and Fabrication Notes: Includes
detailed notes and specifications for the manufacturer regarding assembly
processes, material requirements, and any special
handling or processing needs. The Unisoft software creates process assembly
documents.
Supply Chain Considerations -
DFM / DFA / DFT can extend to include considerations of the supply chain, such as the
availability of components, lead times, and the impact of using
alternate parts.
Early consideration of these factors can help in avoiding delays and redesigns due to parts being unavailable or
having longer than expected lead times.
The Unisoft
software lookup by manufactures part number, etc. feature can aid in this
area.
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