Registration Principle to Compensate for Dimensional Variation of Printed Circuit Boards
Original Publication Date: 1995-May-01
Included in the Prior Art Database: 2005-Mar-30
This article describes a registration principle to compensate for dimensional variation of printed circuit boards at expose steps for primary imaging of photo resist and expose of photoimageable solder mask material, to allow for best fit overlay.
Registration Principle to Compensate for Dimensional
Printed Circuit Boards
describes a registration principle to compensate
for dimensional variation of printed circuit boards at expose steps
for primary imaging of photo resist and expose of photoimageable
solder mask material, to allow for best fit overlay.
circuited board manufacturing the product changes
its size through water absorption or drying as a result of various
processes. The size is also influenced through material remove
related stress relieve. This effect is more visible with thinner
printed circuit boards and even more with thin foils (i.e.,
systems for printed circuit board expose typically
operate with one single artwork on one single panel in off-, soft- or
hardcontact expose mode. As a result this means that the artwork has
to have the correct size for the panel at the point of exposing to
meet the required overlay tolerance.
Due to the
fact of inhomogenity of shrinkage behaviour of the
printed circuit board there is some variation from panel to panel and
from lot to lot. For tighter tolerance requirements and to improve
process capability it is desirable to compensate for the effects
listed above when necessary.
described herein intends to split the error in
fractions. Half, quarter, eighth.. (1/n) of the dimensional error
will only be there, to cause mismatch of overlay by individually
aligning half, quarter, eighth ... (1/n) of the artwork in optimum
position to the corresponding area of the printed circuit board.
Automated covers, shutters, shades, apertures, lenses or other
mechanic or optic devices protect the not optimised area from
exposure. This process will be repeated for all sections of the
moving the artwork to the corresponding optimum
position of the board, it might stay in a fixed position and the
board is moved.
seperates the physical size and dimensional
instability influence from the actual smaller image on the board.
expose system utilises detection systems to
analyse positions of plated or nonplated holes or etched or plated
pattern on or in the printed circuit board on significant positions
on the boards. Depending on further applications, and process