Comparison of advantages and disadvantages of SMT stencil processing methods
The initial SMT stencil manufacturing process is mainly photographic and then chemical etching. Of course, there is also the laser cutting method or electroforming method to process the SMT stencil. In the process of continuous production and processing of SMT stencil, it is found that the three processing methods outlined above have their own advantages and disadvantages, the following will be the advantages and disadvantages of these three SMT stencil processing methods for comparison.
First, the chemical etching method is the earliest processing method used for SMT stencil processing.
Advantages of chemical etching method: chemical etching for SMT stencil leakage hole processing, without expensive investment in equipment, processing costs are relatively low.
Disadvantages of chemical etching method: the time of corrosion is too short, the hole wall of SMT stencil may have sharp corners, and the size of the hole wall may be enlarged when the time is too long, and the side corrosion also makes the hole wall less smooth. Accuracy can not be mastered very accurately.
Second, the laser processing method is currently the most commonly used SMT stencil processing method, which relies on laser energy to melt the metal, and then cut out the opening in the stainless steel plate.
Advantages of laser processing method: the processing speed is much faster than the chemical etching method, and the stencil opening size or control, especially the added hole wall is a certain taper (taper about 2 degrees) is easier to release the mold.
Disadvantages of laser processing method: When the SMT stencil openings are dense, the local high temperature generated by the laser sometimes makes the adjacent hole wall deformation, and the roughness of the metal hole wall formed by melting is not high, so when necessary, the hole wall trimming. In addition, the laser processing method requires special equipment and increases processing costs.
Nowadays, SMT stencil processing method is completed by laser cutting, laser cutting using file data production, high precision and small tolerance.
Third, the electroforming method is a process that relies on metal materials (mainly nickel) to continuously build up and accumulate to form a metal SMT stencil.
Advantages of electroforming method: method made of SMT stencil not only opening size precision, smooth hole wall, conducive to the quantitative distribution of printing solder paste, and the opening is not easy to be blocked by solder paste, thus reducing the number of times to clean the SMT stencil.
Disadvantages of electroforming method: The cost of manufacturing SMT stencil by electroforming method is high and the production cycle is long.
Through continuous research and practice found that both chemical etching method or laser cutting method of SMT stencil processing, printing will appear in varying degrees of opening blockage phenomenon, the need for frequent cleaning of SMT stencil, so electroforming method has become the main processing means of fine pitch components solder paste printing SMT stencil.