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Affect SMT mounter SMT quality element

Time:2019-05-23   |   Source:   |   Compile :9

The three element of SMT machine mounting: component right, location right, pressure

(mounting height) right, next, Grandseed will explain for SMT mounter machine.



1、 The correct placement of components - requires that the type, type, nominal value and character of each component of the assembly number should conform to the assembly drawing and schedule requirements of the product, and cannot be misplaced. 


2、The location is accurate - the end of the component or the pin and the pad pattern should be as close as possible to the 3 inch. 


The placement position of the components of the placement machine must meet the process requirements. Because the effect of the self-positioning effect of the two-end Chip component is relatively large, the two ends of the component length direction should be overlapped on the corresponding pads, and the width direction is 1/2 overlapped on the pad, reflow soldering. It can be self-positioning, but if one of the ends is not attached to the pad, a displacement or suspension bridge will occur during reflow. For SOP, SOJ, QFP, PLCC and other devices, the self-positioning effect is relatively small, and the placement offset cannot be corrected by reflow soldering; therefore, it is necessary to ensure that 3/4 of the pin width is on the pad when mounting. The toe and heel should also be on the pad. If the placement position exceeds the allowable deviation range, it must be manually adjusted and then re-flowed into the reflow oven; otherwise, it must be repaired after reflow, which will cause work hours, material waste, and even affect product reliability. When the production position is found to exceed the allowable deviation range during the production process, the coordinates should be placed in time.


3、The placement machine's placement pressure (patch height) is suitable.


The mounting pressure (height) of the placement machine should be properly and appropriate. The soldering end or the soldered end of the component should be immersed in the solder paste. The amount of solder paste extrusion (length) should be less than 0.2mm for the component placement, and the solder paste extrusion amount (length) for the narrow-pitch component patch should be less than 0.1mm. The pressure of the chip is too small, the soldering end or pin of the component floats on the surface of the solder paste, the solder paste cannot stick to the component, and the positional movement is easy to occur during the transfer and reflow soldering; the pressure of the patch is too large, and the solder paste is excessively extruded. Many, it is easy to cause solder paste adhesion, bridging is easy to occur during reflow, and in serious cases, components will be damaged.