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SMT Technology & SMT Chip Mounter Placement Accuracy

- Aug 21, 2018 -

In the production of SMT , the quality of the placement machine is directly related to the production of the batch, and the technology of the patch in the production of the patch also plays a certain role in the production. The two are directly related to the quality of batch production.

The XY positioning system is the main indicator for evaluating the accuracy of the placement machine. It includes the transmission mechanism and the servo system. The increase of the patch speed means that the running speed of the XY transmission mechanism is increased and the heat is generated, and the ball screw is the main heat source, and the heat is Changes will affect the placement accuracy. The newly developed XY drive system has a cooling system in the guide rail; the high-speed machine uses a frictionless linear motor and an air bearing guide to drive faster.

The SMT patch factory is driven by a synchronous belt-linear bearing. The system has low noise and good working environment.

X Y servo system (positioning control system)

Driven by an AC servo motor and accurately positioned under the command of the sensor and control system, the sensor plays a key role in the accuracy. The displacement sensor has a circular encoder, a magnetic scale and a grating scale.

1. The lenticular encoder is equipped with two lenticular gratings on the rotating part of the grating encoder. The granular grating is made of glass or transparent plastic, and the film is coated with bright and dark radial chrome lines. The adjacent light and dark spacing is called a grid. Section, the total number of total gate segments is the number of line pulses of the encoder. The number of chrome lines also indicates the accuracy. One of the gratings is fixed at the rotating position as the index grating, and the other is moved with the rotation axis and used for counting. Therefore, the index grating and the rotating grating form a pair of scanning systems, which is equivalent to the counting sensor. The encoder is mounted in a servo motor that measures the position, angle and angular acceleration of the rotating part. It converts these physical quantities into electrical signals to the control system. The encoder records the number of pins placed and feeds the information back to the comparator until it is linear. The system is highly resistant to interference, and the measurement accuracy depends on the number of gratings on the grating disk in the encoder and the accuracy of the bead screw guide.

2. Magnetic scale

It consists of a magnetic scale and a head detection circuit that measures the displacement using electromagnetic characteristics and magnetic recording principles. The magnetic scale is recorded on a magnetic film by depositing a magnetic film (generally 10-20 um) on a non-magnetic scale by chemical coating or electroplating on a non-magnetic scale.


A square wave or sine wave magnetic trajectory signal with a certain wavelength for a certain year. The magnetic head moves and reads the magnetic yoke on the magnetic scale, and is converted into an electrical signal input to the control circuit to finally control the operation of the AC servo motor. The advantages of the magnetic scale are simple manufacturing, convenient installation, high stability, large measuring range, measurement accuracy of up to 1~5um, and patching accuracy of generally 0.02mm.

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