Scoring

What is PCOLA/SOQ?

PCOLA/SOQ is a method of assessing the coverage of a test system, that is consistent across different testing technologies. Rather than defining coverage based on only the defects that are detectable within that test framework, it considers all the defects that may be possible on the board.

To determine the possible defects, the following properties are defined for a device or connection.

Device properties (PCOLA)

Presence

Is there a device where a device is expected?

Correctness

Is that device the one that is supposed to be there?

Orientation

Is that device the right way around?

Live

Is the device functioning as it should?

Alignment

How accurately is the device positioned on its pads?

Connection properties (SOQ)

Shorts

Is the pin shorted to another?

Opens

Or maybe it isn't attached to anything?

Quality

How well has the connection been made?

Weights and values

Each of the properties listed above is given a weight, based on how significant it is to the operation of the device, and in its application. The total weight assigned to all properties for a device or connection is 1.

A score is then given to each property, according to how accurately the test system could identify a defect in each of these properties. The score is graded as Full, Partial or None – having a numerical value of 1.0, 0.5 and 0.0 respectively. These properties can also be set to be Ignored and will not be considered in the final calculations.

Calculating circuit element scores

Device Groups

Device groups show the weights to be applied to each of the properties detailed above when calculating overall scores. The Device Score and Connection Score columns then show the average score for devices and connections within the group, as a percentage.

Devices

Devices show the individual scores for the device properties columns - obtained from the parent device group, library file or manual override. The device Score column displays the weighted sum of the device properties for each device. The connection score column shows a combined average score of the device's connections.

Connections

Connections show the scores for the connection properties columns - obtained from the parent device group or manual override. The connection score displays the weighted sum of the connection property values.

Board

Finally, the device and connections scores for the elements within each board are normalised, summed and multiplied by 100,000. These values represent the two overall PCOLA/SOQ scores for that board.

Overall project score

In a project with only one board, the overall PCOLA/SOQ scores displayed at the top of the tab will be the same as the device and connection score of the board. Where a circuit has multiple boards, device and connection scores are normalised across the entire circuit, summed and multiplied by 100,000 to produce the project PCOLA/SOQ score graded out of 100,000.