This page sponsored by

Component movement and lifting are related to the soldering process and the design of the board. If one termination reflows and wets before the other, surface movement, either rotational or vertical, is generated. The different solderability of each termination has also be shown to cause lifting.

The use of vapour phase reflow is more likely to cause movement than convection due to the fluid movement on the board surface. The example in Figure 1 lifted because of the thick solder mask, during reflow it acted like a fulcrum lifting the part just above the pad surface.

Figure 1: Thick solder mask acted like a fulcrum, lifting the part up.

This defect is often referred to as tombstoning, drawbridging or Manhattan skyline, particularly if there are many parts all standing vertically.

The defect is caused by uneven wetting where one termination solders before the second causing the surface tension of the solder to pull the device in one direction. It can be exaggerated by the amount of paste on small parts, 0805 chips and below or incorrect pad sizes increasing movement during reflow.

Figure 2. A component stands straight up here.

Solder paste under components can cause the parts to lift before both terminations have soldered. In this case the same causes attributed to solder beading apply; it is only the end results that are different.

Figure 3. Component lifting has the same causes as solder beading, but a different end result.

Chip Leaching	Component Cracking	Cracked Joint	Crystallized Joints	Failure to Reflow
Joint Failure	Joint Voiding	Lifted Component	Open Joints	PCB Measelling
Plastic Coplanarity	Plastic Softening	Poor Pad Wetting	Poor Solderability & Wetting	Solder Beading
Solder Short	Solder Wicking