Adhesive

Materials used to hold components in place during wave or reflow soldering which may become a permanent part of the assembly, or  be subsequently removed.

Aperture

An opening in the stencil that corresponds to a land area on the circuit to be printed.

Aspect Ratio

A ratio of the thickness of the board to its preplated diameter. A via hole with aspect ratio greater than 3 may be susceptible to cracking.

Azeotrope

A blend of two or more polar and nonpolar solvents that behaves as a single solvent to remove polar and nonpolar contaminants. It has one boiling point like any other single component solvent, but it boils at a lower temperature than either of its constituents. The constituents of the azeotrope cannot be separated by distillation.

Blade Attack Angle

The angle formed between the stencil and the squeegee blade during squeegee travel.

Blowhole

A void in a solder connection created by outgassing during the soldering process.

Bond  Liftoff

The failure condition reflected by the separation of a lead from its bonding pad.

Butt Joint

A surface mount device lead that is sheared, so that the end of the lead contacts the board land pattern.(Also called I lead). Butt joint is made by converting the leads of conventional DIP packages to suit surface mounting.