What are the common causes of poor surface mount technology (SMT) processing in SMT factories?

SMTDuring the production process of surface mount technology (SMT) processing in factories, sometimes some processing defects occur. So, what are the causes of these defects? The following are some common reasons for poor surface mount technology (SMT) processing provided by Shenzhen JJY Solder Paste Manufacturer:

One: Standing upright

The sizes on both sides of the copper foil are not uniform, and the tensile force is uneven. The preheating and heating rate of the machine is too fast. Improper setting of furnace temperature; The components were offset when the machine was mounted. The track clamping plate of the machine is not tight, causing offset during mounting. The head of the machine shakes. The solder paste was offset when printing it. The thickness is uneven when printing solder paste. The temperature distribution in the reflow welding furnace is uneven. The solder paste is too active. All of these can lead to the occurrence of warping.

Two: Offset

During surface mount technology (SMT) processingpcbThe positioning reference points on the board are inaccurate. The reference points of the mesh board andpcbThe positioning reference points on the board are not aligned. The solder paste is missed in the opening of the screen board, which does not conform to the design documents of the circuit board. The circuit board was not fixed properly inside the printing press, resulting in the positioning pin not being in place. The optical positioning system of the printing press has malfunctioned. All of these can lead to the occurrence of offsets.

Three: Short Circuit

When printing solder paste in surface mount technology (SMT) processing, if the distance between the steel mesh and the circuit board is too large, the solder paste will be printed too thickly. The deformation of the scraper on the steel mesh leads to overly thick solder paste printing.

The thickness of the openings in the steel mesh is too thick, the openings in the pins are too long, and the openings are too large. The component mounting height is set too low; Component mounting offset

The reflow soldering furnace heats up too quickly; The solder paste cannot bear the weight of the components. All of these will lead to the occurrence of short circuits.

Four: Missing parts

SMTThe carbon sheet of the vacuum pump of the factory's surface mount machine is faulty, resulting in insufficient vacuum. Faulty suction nozzle or clogged suction nozzle; Suction nozzle, excessive air blowing or no air blowing; There is damage to the trachea in the head. The sealing ring of the air valve is worn. The height setting for mounting is incorrect. Poor detection of component thickness or improper detector; There is a foreign object beside the track of the reflow welding furnace. All of these will lead to the occurrence of missing parts.

Five: Empty welding

SMTThe surface mount technology (SMT) machine in the factory has a deviation during the mounting process. The activity of solder paste is relatively weak. The perforation of the steel mesh is poor. The pressure of the scraper is too high. The distance between copper and platinum is too large or too large, and small components are attached to copper. The flatness of the foot pedal components is not good. The preheating zone of the reflow soldering furnace heats up too quickly.PCBThe board is too dirty or oxidized.PCBThe board contains moisture. All of these will lead to the occurrence of empty welding.

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