Stencil looks like a thin metal sheet, but it plays a very important role in the PCB assembly process.
The primary function of the stencil is to facilitate solder paste deposition, that is to say, transfer a precise amount of material (solder pasteto its exact location on the pads of the PCB. |
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There're three popular technologies for stencil manufacturing: chemical etching, laser cutting and electroforming. Each has distinct advantages and disadvantages. All of these techonlogies has it's own advantages and disadvantages.
Chemical etching is the most cost effective and the quickest, but lack of accuracy, and only reliable for those pitch distance greater than 60 mils applications.
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Electropolishing is achieved by attaching the foil to electrodes and immersing it in an acid bath. The surface of metal is "smoothed" during this process, this resulting in reduce the friction of surface, improve the good paste release. The disadvantage of Electropolishing is the long delivery time.
Laser cut stencil (shown left) offerring very good accuracy and fast turn around time. It's easy to obtain 16 mils pitch with laser technology, positioning accuracy may reach +-1mil. Photographic steps are not necessary for laser cut stencils, it obtains directly from gerber file, this porcess make the possiblilty of misregistration almost to zero. |
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Besides stencils used in PCB assembly, rework stencils are also widely used today. These stencils are very small, most like the size of a stamp. It is designed for a individual components. The rework stencils is most widely used in ball grid array (BGA) chips assembly and rework. |
Conerning about the accuracy and turn around time, EzPCB provide only laser cut stencils. Our laser cutter provide very good manuacturing facility and precision. Most stencils could be deliveried in 2-3 days. Our customers don't need to worry about the high cost of laser cut stencils at all. Our price for stencil is also the most competitive as all the other products of ours. The price for stencil start from only $60.
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