SMT steel mesh is used for the liquid and solid state of solder paste printing on the PCB board, circuit board in addition to the power board most popular now use SMT technology, there are many table paste bonding pad on the PCB, namely without hole welding way, and the steel mesh hole is corresponding to the bonding pad on the PCB, manual brush the level of tin in hard brush will be half of liquid and solid The tin paste in the body state is brushed onto the PCB board through the holes in the steel net, and then the components are pasted on SMT machine, and then the components are formed by reflow oven.
I. Opening principle of SMT steel mesh
1. CHIP type components three times according to the total area of 10~15[%], keep the same distance, and then modify according to the requirements of lead.
2. IC type components (including row insert) length to the additional 0.1-0.20mm, the width of the lead requirements to modify, can be appropriately widened
3. resistance and capacity type components, the length of the additional 0.1mm. Width can be modified according to the requirement of lead
Other components remain the same as the above requirements.
II. Acceptance of SMT steel mesh
1. steel mesh tension 35≤F≤50 (N/cm) tension error: F is less than or equal to 8 (N/cm).
2. steel mesh appearance: net surface without scratch marks, no bump.
3. Before the production of new steel mesh, properly install the steel mesh on the printing machine, and try to print 2~5 plates to confirm the printing effect.
4. After the trial production is passed, record the production time in the relevant documents of steel grid management.
III. Requirements for printing format of SMT steel mesh
1. When one board and one net, the position of the opening graph should be centered.
2. When two different PCB boards are opened in the same steel net, it is required that the edges of the two boards be separated by 30mm.
3. When two same PCB are opened on a steel net, the interval between the two plates of 180° assembly is required to be 30mm.
Post time: Jun-10-2021