Test Point

This rule checks the test point/via number and clearance of net.

Maintaining minimum test point distance from one test point to another is important. Test points which are designed too close to each other present the possibility they will interfere with one another and cause the test not to be performed effectively, thus reducing the test coverage area.

Test point distribution is an important factor, as well. A high density of test points or clusters should be avoided. Test points should be uniformly distributed throughout the board, making it easier to test with multiple probes and not having to rely on a specific area for all the probes to concentrate on.

Accessibility of the net through vias must be available if test points are not available or not designed in.

Pads should be designed slightly larger, if very fine pitch components are involved, to give better access contact points to the test nodes.

Two types of check can be performed:
  • Check number of test points/vias per net.
  • Check clearance among test point/vias.
The two checks can be done independently or together:
  • Test Point Component Group: Click the component group selection button then select a test point component group.
  • Target Layer: Check test points on Top layer only, on Bottom layer only or on All layers.
  • Via: You can use a Via as a test point.
    • All: Use all Vias as a test point.
    • Size: Only specified size of via can be checked. Click to open the Via dialog.Via size can be defined by Drill Size or Pad Shape Size.
    • Size criteria
      • Min ~ Max: Between the minimum (③) and maximum (④) values.
      • Min~: Bigger than the minimum value (③).
      • ~Max: Smaller than the maximum value (④).
      • Size: Match the exact size defined in (③).
    • Min: Minimum size.
    • Max: Maximum size.

Test Point Count Test

Test the count of test point of specific net.
  • Item: Rule name that will be referenced in the report.
  • Net: Target net group.
  • Count: Minimum number of required test points and vias when via option is enabled.
  • Remainder: When it is checked, nets that are not selected in ② are checked against the number of test points entered in the box ⑤.

Test Point Clearance of Each Net Group

Test separation of test point.
  • Item: Rule check item name that will be referenced in the report.
  • Net1: Target net group 1.
  • Net2: Target net group 2.
  • Clearance: Clearance among vias and test points in the two net groups.
  • Remainder: Nets that are not selected in ② and ③ are checked against the number of test points entered in the box ⑥.
Example In-Circuit-Test (ICT) Sequence
  • Discharging capacitors and especially electrolytic capacitors (for safety and measurement stability, this test sequence must be done first before testing any other items).
  • Contact Test (To verify the test system is connected to the Unit Under Test (UUT).
  • Shorts testing (Test for solder shorts and opens).
  • Analog tests (Test all analog components for placement and correct value).
  • Test for defective open pins on devices.
  • Power up UUT.
  • Powered analog (Test for correct operation of analog components such as regulators and op-amps).
  • Powered digital (Test the operation of digital components and Boundary scan devices).
  • JTAG (Joint Test Action Group) Boundary scan tests.
  • Flash, ISP and another device programming.
  • Bead probe.
  • Discharging capacitors as UUT is powered down.