Placement Nozzle Selection, Wear and Management

The nozzle is the last item in the placement chain before the component lands. It decides how the part is picked, how firmly it is held, and how it is released, and a worn nozzle produces placement defects that are usually blamed on the machine.

What the Nozzle Has to Match

The nozzle tip must match the shape and the size of the component body. A tip that is too large picks up neighbouring parts or masks the vision system; one that is too small leaves the part able to rotate on the tip.

The vacuum port must be matched to the part mass. A small part on a large nozzle needs more vacuum than the part can take without being drawn into the tip, and a large part on a small nozzle will shift during the move.

Nozzle Types

The common types are the flat tip for chip components, the cup for parts that need centring, and the special shapes for connectors, modules and odd form parts.

Where the same nozzle is used for several parts, the requirement is set by the smallest part it has to place, and the largest part is limited by the vacuum the nozzle can deliver. Our component selection notes describe how the package decides the handling.

Wear and Contamination

The tip wears at the contact surface and the bore blocks with flux and debris. Both change the vacuum, and the change is gradual enough that it is not noticed until the placement defects appear.

The wear pattern should be inspected under magnification on a defined interval, and the nozzle replaced rather than dressed. A dressed tip loses its reference surface and the pick height changes.

Pick and Place Parameters

The pick height, the dwell and the vacuum delay are set together with the nozzle. A nozzle that has been replaced with a different tip length changes the pick height if the parameter is left unadjusted.

The placement force must also suit the part. A force that is high enough to seat a large part will crush the paste under a small one and leave it uneven. Our paste volume notes describe the consequence for the joint.

Vision and Centring

The vision system measures the part on the nozzle, so the nozzle must present the part without obscuring the features the system uses. A nozzle that covers one corner of a part with a polarity mark prevents the polarity check.

Where the part is centred mechanically rather than optically, the nozzle and the centring jaws must match the package, or the part is placed with a consistent offset. Our inspection notes describe how the offset is detected.

Nozzle Management

The nozzle set for a product should be listed with the part it places, and the list should be part of the machine setup rather than held in the operator’s knowledge.

The nozzle bank should be inspected and cleaned on a schedule, and each nozzle should be identified so that a worn one can be traced to the boards it produced. Our fabrication notes notes list the setup records that should be kept.

Verification

The nozzle is verified by the placement accuracy measurement that the machine can perform, and by the defect rate by part type. A rise in one part type points at the nozzle or the feeder rather than at the program.

The vacuum should be measured at the tip rather than read from the machine display, because a leak between the sensor and the tip is exactly what the measurement is meant to find. Our quality notes describe how the result is recorded.

Process Control and Verification

Running a first article through the same checks as the production panel confirms that the two agree, and that comparison is the cheapest form of process control available at prototype stage. Keeping a sample from the panel turns a dispute into a measurement, because the same coupon can be re-examined by both parties without rebuilding the batch.

Reviewing the design before the data is released is cheaper than correcting it after the panel is in the tank, because every step downstream inherits the decision made at the front end. Documenting the assumption is part of the design work, and a short note on the drawing prevents a question that would otherwise arrive a day later and cost a day of schedule.

The process window is set by the narrowest step in the flow, so an improvement anywhere else shows up as margin rather than as yield until that step is addressed.

Checks Before Release

The checks that matter are the ones performed on the product rather than on a sample kept for the purpose, because a coupon that travels with the panel is the only evidence about that panel. Where a requirement can be measured, it should be measured at the point of manufacture and recorded against the board or the lot it applies to.

A parameter that is set once and never re verified drifts, and the drift is usually discovered by a defect rather than by the record. The tooling, the material and the profile form one system, and a change to any of them should be assessed against the other two before it is released.

Where the process window is narrow, the measurement resolution has to be better than the window, or the data cannot distinguish a good part from a marginal one. A record that identifies the operator, the date and the settings is worth more than a record that identifies only the result.

Verification and Records

The acceptance criteria should be written before the work starts, so that the decision is made by the specification rather than by the person inspecting. Where an operation cannot be verified afterwards, it has to be controlled during the operation, and that control has to be visible in the record.

Sampling is a compromise between cost and confidence, and the sample size should follow from the failure rate that has to be detected.

FAQ

Can one nozzle place every part on a board? Rarely. The tip has to match the smallest part and the vacuum has to carry the heaviest, and those two requirements pull in opposite directions.

How often should nozzles be replaced? On a measured wear interval rather than on failure. A nozzle that has begun to produce defects has already produced boards.

What does gopcb provide for nozzle control? We provide nozzle selection by package and mass, tip and vacuum matching, pick and place parameter development for the nozzle, wear inspection on a defined interval with replacement rather than dressing, nozzle identification for traceability, and accuracy verification by part type.