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How to Use an SMT Stencil

The electronics industry has largely replaced the through-hole method of printed circuit board construction with the surface mount technology or SMT method. Instead of using component leads that are inserted into holes in the circuit board, SMT uses a stencil to transfer solder paste onto the surface of a bare board. Surface mount devices (SMD) are then soldered to those contact points.

Why to Use SMT Stencils
Some of the advantages of using SMT stencils include:

- Enables the use of smaller components

- SMT parts are usually cheaper

- Assembly can be more easily automated

- Components can be placed on both sides of a board

- With lower resistance, high frequency parts perform better

Using SMT Prototype Stencils

SMT stencils are quickly becoming a useful prototyping to for circuit board construction

The general process for using a prototype stencil is described below:

1. Secure your board to a work table using some type of right angle support on the bottom and top of the board. Be careful to keep tape from touching the surface of the board

2. Align the stencil over the SMT pads on the circuit board and tape it down to secure it.

3. Place a line of solder on one side of the stencil

4. Use a rubberized squeegee to push the solder paste into the apertures

5. Remove the stencil from the board

6. Apply components to the solder past connection

7. Follow manufacturer’s safety tips when heating the board for re-flow soldering

See a SMT stencil being used.

More complex designs may require additional steps, but these steps are generally all there is to using a SMT prototype stencil.