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PCB manufacturing SMT printing process parameter design

65 Published by FASTPCBA 9月 27,2019

PCB manufacturing SMT printing process parameter design

SMT processing stencil printing is the most basic SMT processing solder paste printing method. Although there are many modern PCB manufacturing printing equipments, the basic printing process is the same.

SMT

SMT

(1) Printing preparation. Prior to printing, the operator of the printing machine had to prepare for the PCB manufacturing and printing, and the preparation was mainly divided into three categories. The first category: fixture preparation, preparation of stencil, scrapers, tools such as hexagonal screwdrivers; the second category: material preparation, preparation of solder paste, PCBs filled with turnover boxes, alcohol, wiping paper, etc.; third category: documents Preparation, prepare assembly technical documents, process cards, precautions, etc.

 

(2) Install the stencil and scraper. Install the stencil, insert it into the template rail and push it to the last position to clamp it, unscrew the air brake switch and fix it.

The scraper installation, and the appropriate scraper is selected according to the production process of the product to be assembled. Generally, the stainless steel scraper is selected, especially when the high-density assembly is used, and the tail scraper is used for installation.

 

  • PCB positioning and graphic alignment. The purpose of PCB positioning is to initially adjust the PCB to the position corresponding to the template image. The substrate positioning method has hole positioning, edge positioning, and vacuum positioning.

 

Hole positioning: semi-automatic equipment, visual system is required for higher precision requirements, and special positioning column is required.

 

Edge positioning: automated equipment, requiring optical positioning, high requirements substrate thickness and flatness .

Vacuum positioning: Powerful vacuum suction is the key to ensuring print quality.

 

  • Set the process parameters. The main parameters are blade pressure, blade speed, blade angle, blade selection, separation speed, printing gap, printing stroke, cleaning mode and frequency.

 

(5) Add solder paste and print. A small spatula is used to evenly apply the solder paste behind the stencil pattern of the stencil along the width of the squeegee. The solder paste cannot be applied to the holes of the stencil.

 

  • Analysis of stencil printing results. The amount of printed solder paste is uniform ; the solder paste pattern is clear, and the adjacent patterns are not adhered as much as possible; in the pcb manufacturing patch, the solder paste pattern and the land pattern should not be misaligned as much as possible.

 

(7) Analysis of solder paste printing defects.

 

 

 

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