Stencil is huge critical to PCB assembly process, which directly determines the uniformity and sufficiency of every single welding pad, and then the stability of PCB after SMT assembly and reflow oven soldering. In general, we have to carefully analyze basic attributes and positioning of PCB before heading for PCB stencil. In terms of high precision and quality PCB, we must use laser stencil. It is highly recommended to raise a special meeting between engineers, confirming manufacturing process with final results such as appropriately widening stencil holes to ensure solder pasting effects.
With regard to PCB stencil fabrication, we have to concern about:
1. ME makes stencil according to customer request documents.
2. The framework dimension of stencil (such as 550mm*650mm, 370mm*470mm on basis of screen printer and product dimension)
3. Signs on stencil (product NO., thickness, production date)
4. Thickness of stencil (such as 0.18-0.2mm, 0.1mm-0.15mm)
5. Stencil cut method and size (such as V, U, concave type on basis of components)
6. Same direction with SMT machine.
Attentions to PCB stencil acceptance, check cut method and dimension, stencil thickness, framework dimension, signs on stencil, flatness, tension, cut quantities same with gerber files in compliance with customer request. Stencil fabrication is critical process during whole quality management, so engineers should pay great attentions to. Customer should not deliberately save cost to cause a result of inappropriate soldering and delayed production schedule.