Tombstone Analysis

Ribbon Tombstone Analysis The tombstone effect describes a phenomenon where small smt components (like resistors or capacitors) are partially or completely lifted from one of its copper pads (looking like a tombestone in a cemetery) during reflow soldering.PCB-Investigator helps to find those critical components and to avoid defects.

Tombstone Analysis

The 'Tombstone Analysis' takes a detailed view on every small 2-pin component, as they are the most endangered for defects caused by the so called tombstone effect. The analysis checks the difference in the pin connection of the two pins for each component. The higher the pin connection differences (e.g. 100µm on Pin1 and 400µm on Pin2), the more uneven is the heat expansion and therefore the cooling-down after the reflow process. When a pin is cooling down much faster than another one, there is an unintended mechanical tension, which might lift up the component on one pin - the so called tombstone effect.

Settings:

Tombstone Analysis Setting

 

  1. You have different options, you can activate/deactivate in the menu:
    • Show Types: When checked, there will be an additional column in the result tabs, giving information about the pad symbol types (e.g. round/rect/oct/... + size).
    • Show Geometry: When checked, there will be an additional 'geometry' column in the result tabs, giving information about the package name of the component.
    • Optimize View in double click: When checked, a double click on a reported component will show this component in the main drawing window including the size labels for the pads/tracks.
    • One Tab per Geometry: When active, you will get one result tab per component geometry. If not, all results are listed in one single result tab.
    • Create Difference Diagram: If checked, there will be an additional result tab with a graph showing the amount of violations per risk category.
    • Including Drill Connections: If checked, the pin connection by a 'via in pad' is also considered with the circumference of the drill as connection width.
    • Save Result for Extended Design Report: If active, the result can be exported with the 'Extended Design Report' plugin.
  2. In this list you can select the component geometries, which should be analyzed. The amount of components and the package size is also shown. Only components with 2 pins are listed.
  3. Click here to start the analysis.

 

Example:
Pin 2 of a C2320 is connected with 1000µm, Pin 1 with only 400µm. This is a difference of 150%
Tombstone Analysis Example

The orange lines could not exactly be calculated  (due to e.g. overlapping of tracks) and should be reviewed in every case.
The list can be sorted and filtered by using the filter box in the column header.