Electrical Test
What is Electrical Test?
The term Electrical Test (ET) is widely used across various industries, but what does it really mean?
Electrical Test is an evaluation of the parametric, functional, or timing performance of a component when electrical power is applied. Parametric tests typically involve a DC source and measures current or voltage. The current or voltage is measured to validate that the connection point has the expected voltage or current, hence creating the ‘TEST’.


When performing Electrical Test on unpopulated PCB’s the process uses requirements that are documented on the fabrication drawing (master build drawing). These requirements will vary from part to part and should be set by the design engineer.
Unpopulated (Bare) PCB Electrical Test: This is a test that is run after the circuit board has been fabricated to make sure that all nets in the board have electrical connectivity. The test can also be performed in the fabrication process before the final solder resist coat is applied (solder mask). The test could also be performed on a single PCB layer or on a sequential lamination fabrication panel.
Electrical Test follows the base principals of Ohms Law. Ohm’s Law is a formula used to calculate the relationship between voltage, current and resistance in an electrical circuit.
V – Voltage
I – Current
R – Resistance
V= I x R
When Electrical Test is performed typically resistance is used as the base measurement so Ohms Law would be
When voltage is applied to the net current flows allowing the resistance of the PCB trace to be measured.
R= V / I

What is a short circuit?
Electrical Test is an evaluation of the parametric, functional, or timing performance of a component when electrical power is applied. Parametric tests typically involve a DC source and measures current or voltage. The current or voltage is measured to validate that the connection point has the expected voltage or current, hence creating the ‘TEST’.

What is an open circuit?
What is a netlist?
The flat file called IPC-356 by IPC International Inc (IPC) coming from the schematic drawing can be used to verify the PCB fabrication process by comparing the IPC-356 generated from the schematic drawing to the IPC-356 file generated from the PCB manufacturing data. If there are any discrepancies found they should be reviewed before the fabrication process is initiated.
When using a third-party Electrical Test provider this process can be enhanced by the provider using the original design files (Gerber, ODB++, DPF, etc) and comparing these files to the fabricators IPC-356 file.

Testable Points on a PCB
Electrical Test points on an unpopulated PCB can defined by any open surface finish area on the PCB that can conduct electricity. The Electrical Test process may utilize all open areas or perform some test point optimization to reduce production costs. The best practice to ensure the electrical integrity is met for your design is to clearly define how the test points should be assigned. If adequate test point coverage is not provided for in the design, the manufacturer may resort to other less expensive options.
All these areas may end up passing the minimum testing rules that you have set up for your layout, but they may not be the most optimum conditions for the final product. By taking the time to look at these areas from a functionality perspective, the final assembly will have the in-circuit test points (ICT) that will ensure a seamless final product. Clearly define the Electrical Test point coverage on your manufacture’s fabrication drawing.
Testable test points on a PCB should have a suitable conductive area that is free of non-conductive material like solder mask.

The above example shows a shift in the conductive area and may not be able to be tested on some fixed mechanical test types.
Possible Test Points on a PCB
Points A & B could have test points on them
Points C & D are not testable because there is no conductive material on the outer surface
Point E is not testable because there is no conductive material
Point F could have test points
Hole 2- buried via, point H is not testable because the outer surface is not electrically conductive
Hole 3- PTH, points I & J could be tested
Via hole 5, could be tested
Point N cannot be tested because there is not conductive material
Point M cannot be tested because there is not conductive material
Interested?
We offer our services under 2 distinct frameworks: the OnDemand Solution and the Integrate Solution.
Depending on your needs, you can either outsource specific testing requirements or we can completely run your test area or test department on your behalf. Contact us now and we’ll find the best solution for your business.