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54 SMT Magazine • January 2015 Speaking of boards, an obvious consider- ation is the board size that the machine will accommodate. If you are running a number of different boards of varying sizes, be sure the stencil printer can handle your largest size. Ma- chines can vary among manufacturers, accom- modating board sizes from as small as 1" square to as large as a square meter or more, so make sure your equipment provider can handle your specific needs. Another factor affecting print quality is the squeegee type. Squeegee blades are made from several materials and come in a variety of siz- es. Blade types are commonly urethane, metal (most popular), and plastic. Metal squeegee blades typically enable a more controlled print height across the board and work well with a mix of component sizes. Some users consider the stencil print- er to be the most important purchase of all—consider this quote from the Adafruit forum: Spending money on a good stencil printer is a really good idea. You live and die by the quality of the solder paste deposit on your PCB. vendor Support One of the most important aspects of this evaluation (for any SMT machine, frankly) will be support, and the best way to learn how a company treats its cus- tomers is by word of mouth. Talk to sev- eral customers to find out how happy they are with the machine, the seller, and the support they provide. Where is the man- ufacturing plant? Can they help trouble- shoot software or alignment issues over the phone? Do they offer field service? Do they have spare parts in stock for immediate shipment? Remember to ask your supplier about their older machines in the field, and if down the road, spare parts are available, and about their capability to customize a spare part if the machine becomes obso- lescent. Ask what the expected life-cycle of the product is. The industry standard is seven years. Remember, there is a difference between a true manufacturer and an equip- ment supplier or distributor. Double-sided Boards or flexible Circuits? Do you need a method to print both sides of the board? Check to see that the model you're considering offers a double-sided nesting fix- ture or vacuum fixture to hold down flexible circuits. Ease of use Every stencil manufacturer makes different size frames. The stencil printer you buy should be able to accommodate various size mounting frames and/or tubular frames. The manufac- turer should also be able to provide adapters for frameless stencils. Don't overlook electrical requirements. Make sure the machine you buy will plug- and-play in your environment without pull- Figure 3: View of squeegee. HOW TO SELECT a STEnCIL PrInTEr continues smt quiCk tiPs