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Preventive Maintenance For SMT Pick-and-place Nozzles

Dafton Electronic Co.,Limited | Updated: Nov 05, 2018

The lack of proper nozzle maintenance and/or poor-quality nozzles will lead to part issues, machine issues, and other process problems. Careful review of these processes has determined the following five major issues associated with improper nozzle maintenance and/or the use of poor quality nozzles.

Loss of vacuum. Vacuum loss may be responsible for some issues, as it can prevent the nozzle from picking up a component from the feeder. It also could cause components to shift on the nozzle during transport. The quality and structure of the nozzle must match the component it is designed to place. Another issue related to loss of vacuum is poor pick-up location on the component. Poor-quality nozzles can cause extra fatigue on the pick-and-place equipment as it must constantly acclimatize to maintain efficiency.

Short or worn nozzles. Short or worn nozzles result in poor pick up and can cause the part not to be embedded correctly into the solder paste. When the part is not placed into the solder paste correctly, there is not enough surface tension to hold the part while the PCB is moving. Parts will shift on the board. One benefit of monitoring nozzle tip length is that it can allow scheduled preventive maintenance to prevent nozzle tips from causing quality issues.

Nozzle tip wear can also cause less vacuum to be generated, allowing electronic parts to drop or shift during transport.

Sticking nozzles. When a nozzle sticks, it drastically changes the height at which the nozzle is presented. There are a few things that may cause this to happen. One of the most prominent is the quality of the material used to manufacture the nozzle. Over time, certain plastics and metals can deform, causing the nozzle to not fit correctly in its holder. This results in the nozzle sticking during the picking, transport, or placement stages.

Higher than normal rejection rate at inspection. Causes for higher failures at SMT inspection include:

1).components were not presented to the nozzle in a consistent position;

2).poor nozzle lighting from degradation of reflective disks or nozzle face over time, dirty reflective disks or nozzle face, or poor quality of reflective disks or nozzle face;

3).nozzle height is incorrect;

4).stuck nozzles from part height incorrectly set in program, nozzles worn beyond their tolerances, or incorrect length tolerances on nozzles.

Component and circuit board damage (caused by ESD). With the constant movement of nozzles and components, it is possible to build electrostatic charges (ESD) on the nozzle tips. Once released, this charge can damage component and circuit board.