There are a variety of configurations of SMT stencils used in differing situations. Framed SMT stencils are used in semi and automated SMT stencil printing machines and provide stability, rigidity and co-planarity for the numerous production cycles it will “see” during its lifetime. A subset of these framed stencils are “frameless” stencils or ones that use a variety of different reusable frames which allow stencils to be used in and out these frames thereby reducing the individual cost of the stencils while still providing the rigidity of the previously-mentioned framed variety. Finally, those SMT stencils are used for prototyping where speed is of the essence and hand printing is the process of choice and lowest possible cost is required as there are many versions of the prototype.
The prototype SMT stencil is a frameless stencil used when only a few boards are being produced and hand or manual stencil printing will be utilized. The materials used for these types of stencils can be either stainless steel or Kapton™. Stainless steel is used when there are ultrafine pitches and the board in question has a larger print area. Kapton ™ stencils are used when the pitches are fairly robust, and the distance between devices is spaced a reasonable distance apart from one another.
A prototype stainless steel stencil is configuring in a few different ways. In one configuration the edges of the stainless are flipped up and create a barrier to capture the solder paste when printing. This is done when the print area is 8 x 8 inches or less. A second prototype stainless steel stencil configuration is when a foil only is produced. In this configuration, as the name implies, only a simple metal foil with the appropriate apertures, is supplied. Finally, a complete SMT prototype SMT stencil kit is supplied which includes the stencil, a squeegee and board holders.
A prototype Kapton™ stencil can be supplied in similar configurations. Either a stencil only or SMT prototype stencil kit configuration is supplied when specifying a Kapton stencil. Finally, in other configurations solder paste, either lead free or tin-lead completes the ultimate SMT stencil kit.