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Prevention of Ultra Violet Exposure through Thin Laminate

IP.com Disclosure Number: IPCOM000117918D
Original Publication Date: 1996-Jul-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Jones, GW: AUTHOR [+3]

Abstract

As package density becomes greater, individual layers have decreased in thickness to accommodate more wiring per unit volume. The fully additive electroless process does not use copper foil for circuitization. Without this opaque copper layer, Ultra Violet (UV) light can more readily pass through thin laminates such as epoxy-glass less than about 7 mils thick. This phenomena is referred to as "bleed-through". Bleed-through on thin laminates can cause photoresist on the opposite side to partially polymerize. The result is incomplete development and subsequent copper voids when using the fully additive circuitization process. The affected side is always the first side exposed. However, if both sides are exposed simultaneously, the defect does not occur.

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Prevention of Ultra Violet Exposure through Thin Laminate

      As package density becomes greater, individual layers have
decreased in thickness to accommodate more wiring per unit volume.
The fully additive electroless process does not use copper foil for
circuitization.  Without this opaque copper layer, Ultra Violet (UV)
light can more readily pass through thin laminates such as
epoxy-glass less than about 7 mils thick.  This phenomena is referred
to as "bleed-through".  Bleed-through on thin laminates can cause
photoresist on the opposite side to partially polymerize.  The result
is incomplete development and subsequent copper voids when using the
fully additive circuitization process.  The affected side is always
the first side exposed.  However, if both sides are exposed
simultaneously, the defect does not occur.  A typical expose dose for
this simultaneous expose process would be in the range of 50-60
mJ/cm2.