Nozzle Selection for Odd Form Component Placement Guide

Odd form components are the parts that do not come on tape in a standard package: connectors, shields, transformers, large capacitors, sockets and mechanical hardware. They are placed on the same machine as the chip components, and the tool that picks them up decides whether the placement is repeatable or whether every board needs an operator to nudge the part into position.

What Odd Form Components Require

An odd form part is usually heavier than a chip component, its top surface is often irregular, and its centre of gravity may not be over the pick point. It may also have pins that must enter holes, which turns placement into an insertion task.

Those characteristics rule out the standard nozzle for most of these parts. What is needed is a tool that grips the part positively, holds it square to the board, and can apply a controlled downward force without damaging the body.

Vacuum Nozzles and Tip Geometry

A vacuum nozzle works where the part presents a flat, non porous surface that can be sealed against the tip. The tip geometry has to match the part, because a tip that is too small gives too little holding force and one that is too large may touch neighbouring features.

For a part with an irregular top surface, a custom tip made from a soft material can conform to the surface and seal. A soft tip also absorbs some of the placement force, which reduces the risk of cracking a plastic body. Our land pattern guide covers the pad geometry the part has to land on.

Grippers and Mechanical Holders

A mechanical gripper holds the part by its sides or by a feature, which allows a much higher holding force than vacuum. Grippers are used for heavy connectors, for parts with holes and for anything that has to be pushed into place.

The gripper has to be designed so that it does not mark or deform the part, and so that the closing force is repeatable. Where the part is fragile, a compliant jaw material is used, and the closing force is set as low as the pick reliability allows.

Placement Force and Its Control

The placement force is what drives the part onto the paste and, for a pin in hole part, into the hole. Too little force leaves the part sitting on top of the paste, while too much drives paste out from under the pad or deforms the part.

The machine usually controls the force through a spring, a pneumatic regulator or a force sensor. Where a force sensor is fitted, the value should be set for the weakest part in the product rather than the heaviest, and the setting should be recorded.

Nozzle Wear and Maintenance

A nozzle wears at the tip, where it contacts the part and the board. A worn tip loses its sealing surface and its holding force, and it may also pick up flux and paste that transfer to the next part.

Nozzles should be cleaned on a schedule and inspected for wear, and the pressure should be checked against the specification. A nozzle that has lost its vacuum will usually be noticed as a rise in pickup errors rather than as a placement defect.

Feeding and Presentation

An odd form part may arrive in a tray, a tube, a matrix tray or a custom feeder. The presentation has to locate the part precisely enough that the machine can pick it at a defined position, because the vision system may not be able to see a feature it can align to.

Where the part is supplied loose, a tray with pockets sized to the part gives the consistency the machine needs. Our component guide covers the handling and storage that keep the parts in condition before placement.

Placement Accuracy and Vision

Vision alignment is harder for an odd form part because the features used for alignment may be at the bottom of the part, where the camera cannot see them. The alignment often has to be based on the body outline or on the leads.

Where the machine cannot align the part, a mechanical alignment station or a custom fixture is used. The accuracy then depends on the tray position rather than on the vision system. Our quality documentation describes how these results are classified at gopcb.

Common Problems

The common problems are pickup errors, parts that rotate after pickup, placement offset, parts that are not fully seated in their holes and paste that is disturbed by a heavy part. Each of them points at a different part of the tooling.

A part that rotates after pickup usually indicates insufficient holding force or an off centre pick, while a part that is not fully seated usually indicates insufficient placement force or a poor lead to hole alignment.

Process Control Points

The controls are the nozzle or gripper specification and its condition, the vacuum or closing force, the placement force, the tray position, the vision alignment method and the inspection of the placed part.

Each of those should be recorded in the placement program and checked at the first article. Our production flow guide places odd form placement in the wider assembly sequence, where it usually sits alongside the standard placement step.

Process Control and Verification

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.

FAQ

Can odd form parts be placed on a standard machine? Many can, with a custom nozzle or gripper and a suitable feeder. The limits are the part mass, the surface available for pickup and whether the leads must enter holes.

Why does an odd form part rotate after pickup? Usually because the holding force is too low or the part was picked off centre. Both are corrected by reviewing the tip design and the pick position.

How is placement force set for a mixed product? The setting should suit the weakest part on the board rather than the heaviest, and it should be verified on the first article.