① Types of surface mount components: almost all traditional electronic components are covered.
② Volume of surface mount components: Taking chip components as an example, commonly used chip resistors range from 6.14mm3 (3216) to 0.0096mm3 (0402), with a difference of about 640 times.
③ The top surface materials of surface mount components: ceramics, metals, various plastics and other materials with different surface smoothness and smoothness.
(2) Mounting speed
Because there are at least a few and dozens of components on a circuit board, and dozens or hundreds at most, hundreds to thousands of components, and these components can only be mounted one by one, so in order to improve efficiency At present, the mounting time of each component has been shortened to about 0.06 s (chip components), which has almost reached the limit of the speed of mechanical structure movement.
(3) Placement accuracy
Due to the ever-increasing assembly density and the application of 0.3 / 0.4 pitch ICs and 0402 components, the placement accuracy is becoming increasingly demanding. Using mechanical, optical, electrical, hardware and software integrated technology, the placement accuracy can now reach 75 μm accuracy under 3 Sigma, and some small components and details are even placed at 50 μm or higher from 4 Sigma. . The distance between components and components and between components and devices reaches the order of 0.1mm, which means that the SMT placement accuracy index has been on the same level as the packaging technology requirements.
(4) Mounting and carrying circuit board
The circuit board carrying the mounted components and the mounting technology are mainly related to the geometric size and the rigidity in the thickness direction of the board. The area of the circuit board can range from a minimum of less than 1 cm2 to a maximum of more than 4000 cm2. The thickness of the circuit board that determines the stiffness in the thickness direction of the circuit board varies from less than 0.5 mm to more than 6 mm (rigid board).