Fluid Velocity
Wave disturbance is the local velocity variation within a molten solder wave that assists the entry of liquid metal into narrow joint spaces. When wave solder turbulence is controlled, the dynamic fluid action overcomes the surface tension of the solder on high-density circuit boards. This agitation is produced by a secondary nozzle that generates a rapid, chaotic flow to break the gas pockets that form around component bodies.
Uncontrolled agitation, however, leads to excessive oxide creation and solder splashing.
Defect Formation
Excessive fluid speed causes the solder to spill over the board surface or escape behind the selective pallets used for protection. This splatter results in micro-solder balls that adhere to the solder mask and can later dislodge to cause electrical shorts. High turbulence also increases the contact of the molten alloy with atmospheric oxygen, generating large quantities of dross.
In order to minimize this oxidization, operators must adjust the pump speed and verify that the nitrogen blanket remains continuous. Precise control of the wave height is also necessary to prevent the liquid metal from lifting the components out of their designated positions.
Output Quality
Reducing this chaotic behavior ensures a smooth exit of the board from the main solder wave. This exit transition is what prevents the formation of solder bridges and icicles on fine-pitch connectors.
