TABLE OF CONTENTS The phrase, Direct Chip Attach (DCA) refers to the assembly of bare die to a package or substrate and applies to SCP, MCP or COB applications [1]. It usually includes a connector as part of the assembly for attachment to Level 3.0 The connecter distinguishes a COB assembly from an MCM-L. COB, historically, has referred to chip and wire assembly of bare die to a second level PWB. COB, in this particular case, is significant because it effectively bypasses assembly of the die into a package and the subsequent assembly of that package to the PWB. As a result it presents itself as a packageless IC packaging option. With elimination of the package there is a significant reduction in both size and weight to be realized. Figure 7-1 contains examples of COB assemblies, a few chip COB and a high density multichip assembly. COB can also be combined with SMT components on the same board as illustrated in Figure 7-2.
With the emergence of the organic substrate as a viable alternative to ceramic COB terminology now applies to SCP (the PBGA) and MCP (an MCM-L) applications covering Level 1.0 and Level 2.0 assemblies.
The COB process involves three basic steps epoxy die attach, wire bonding, and an encapsulation step. Figure 7-3 graphically illustrates the complete COB process. COB utilizes chip & wire...
