Browse Prior Art Database

Stencil to PCB Height Determination

IP.com Disclosure Number: IPCOM000103222D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 43K

Publishing Venue

IBM

Related People

Bessy, A: AUTHOR [+2]

Abstract

Disclosed is a method to accurately and repeatably determine the distance between a stencil and a printed circuit board (PCB) surface for stenciling solder paste. The method allows consistent stenciler setup from operator, eliminating process impacting variability.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Stencil to PCB Height Determination

      Disclosed is a method to accurately and repeatably determine
the distance between a stencil and a printed circuit board (PCB)
surface for stenciling solder paste.  The method allows consistent
stenciler setup from operator, eliminating process impacting
variability.

      Refer to the figure.  The PCB (5) is fixed to the stencil table
(3) and is tightly covered by a sheet of aluminum foil (4) of known
thickness.  Care should be taken so no objects protrude above the PCB
surface and no wrinkles are in the foil over the PCB.  One electrode
from an ohmmeter (2) is attached to the foil, while the other is
attached to the copper stencil (1).  The ohmmeter should be turned on
to measure electrical resistance.  The stencil is then lowered until
the ohmmeter registers a completed electrical circuit.  At this
point, the bottom of the stencil is in contact with the top of the
foil.  Through knowledge of the foil thickness, the distance from the
bottom of the stencil to the top of the PCB is now known. With care,
it is possible to determine this distance to  0.0005 inch or less.

      Disclosed anonymously.