In the printing process, solder paste is coated on the solder pad of PCB by a metal scraper through a wire mesh.

1. Classification of printing parameters

1)Equipment

*Printing accuracy of equipment

*Equipment and process performance

*Equipment stability

2)Stencil

*Production quality

*Area ratio (opening, depth)

*Opening shape

3) Solder Paste

*Size of tin particles

*FluxPrinting stability

*Thixotropy

2.Classification of factors affecting printing

3.Squeegee Type

4.Installation mode of scraper

5.Supporting system

1). The necessary supporting device ensures that the PCB is stable and parallel to the screen to obtain highQuality printing;

2). The vacuum fixed type should consider that the solder paste may be sucked into the through hole, resulting in a lot of small tin ball or bead.

3). The support system shall have considerable flexibility to facilitate replacement.

4). The stability of printing equipment, the parallelism of scraper, screen and PCB are the precondition to ensure good printing stability.

5). Position selection of support system

6.Vision system

The automatic correction ability of printing machine to PCB is an important part of online printing.

The printing press usually uses the reference points of screen and PCB as reference, and moves each other

7.Transmission and transportation device

8.Cleaning system

• online screen cleaning

– program the cleaning mode

– clean the blocked wire mesh with vacuum

– generally dry after wet cleaning

• manual cleaning

– use dust

-free cloth

– clean the screen at the same time on both sides of the screen with a dust-free cloth stained with cleaning solution.

SMT steel mesh cleaning machine

-Ultrasonic cleaning