Stentech's Vacuum Plates provide support for the circuit board during the assembly process. Because we now manufacture highly complex and dense boards, this has become critical to avoid warping, sagging, and bending of the board.
- Vacuum plates will ensure proper support for double-sided boards.
- Consistent board support ensures consistency in paste deposits, reducing reworks and saving money.
- Quick and easy setup is essential in maximizing product throughput.
- Dedicated tooling is the industry standard for ensuring fast and repeatable set-up, and maintaining process stability.The screen print process is full of variables that effect the success of the SMT process as a whole. Dedicated screen print tooling is a proven way to reduce variation and defects.
- Print defects that differ from run to run are often caused by set up variations.
- Varying placement of magnetic pins from set-up to set-up can cause defects that are difficult to troubleshoot. Even under normal squeegee pressure, a board can flex and move if the Z plane of the board is not flat and stable. When a board flexes, the x-y alignment, snap-off, and squeegee pressure are no longer at a constant.
- Defects can also be caused by vacuum seeping through holes to the stencil side of the board, actually drawing the paste out of place. If vacuum is being presented to the entire bottom side of a board, chances are the print quality is suffering.
- Product changeover and set-up time can be a concern when you have more than two per shift. If magnetic pins or sheet metal dams are being used to support the board, they must be placed correctly and that takes time (5 to 20 minutes on average).
Screen print tooling should be designed with the following characteristics:
- To provide maximum support across the board and hold the board in a flat and constant Z plane. Especially under fine pitch components.
- To supply maximum vacuum and avoid vacuum leaks to the stencil side of the board, meaning no vacuum through the holes and vias.
- Dedicated tooling should take less than one minute to change over from product to product.
Because of the varying substrates and component mix in our industry, there is no such thing as a truly universal tool for providing excellent prints. Each product or product family should be evaluated on a case-by-case basis, and the right decision made to yield the best results possible.