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Browse Prior Art Database

Inexpensive Cap Hermetic Encapsulation Process

IP.com Disclosure Number: IPCOM000122054D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 63K

Publishing Venue

IBM

Related People

Emmanuel, SD: AUTHOR

Abstract

High performance multi-level chip (MLC) modules used in mainframe computers are required to meet very low failure rate specifications. To meet these specifications, modules are generally hermetically encapsulated using precisely machined ceramic or metal caps. A process is described in this disclosure to replace these machine caps with a very simple ceramic or metal cap in a simple hermetic incapsulation process.

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Inexpensive Cap Hermetic Encapsulation Process

      High performance multi-level chip (MLC) modules used in
mainframe computers are required to meet very low failure rate
specifications.  To meet these specifications, modules are generally
hermetically encapsulated using precisely machined ceramic or metal
caps.  A process is described in this disclosure to replace these
machine caps with a very simple ceramic or metal cap in a simple
hermetic incapsulation process.

      The proposed method uses a flat ceramic or metal cap which does
not require precise machining.

      The process begins with a normal chip join using solder balls
and C4 pads.  Next, a first eutectic spacer is placed on the
substrate together with a ceramic spacer.  The eutectic seal band
should have a higher melting point than that of the solder balls
joining the semiconductor chip to the substrate.  Alternatively, they
may have the same melting temperature, but the chip join and spacer
band flatten operations must be accomplished in the same furnace
reflow.  A flattening weight may be placed on the seal band or
ceramic spacer to flatten the seal band.

      Next, a seal band is placed on the flat ceramic or metal cap
and flattened through a seal band flattening process through the
furnace.  This preform is melted at a lower temperature than the chip
join solder balls and the seal band preform on the ceramic substrate.
After the seal band on the cap has been flattened, conductiv...