Arrays of Contacts between MCMs with through hole vias

 

In this method, an array of contacts are used to provide the vertical interconnections between stacked MCMs. There are six variants of this method as follows:

• Fuzz buttons in plastic spacer and filled vias in substrate: In this method MCMs are stacked with an intermediate layer called the spacer or fuzz buttons board. This layer has a precision plastic spacer to provide clearance for chip and bond, and fuzz buttons to provide interconnection by applying a mating force on the stacked MCMs as shown in Figure . Fuzz buttons are physically made of fine gold `wire wool' and the integrity of a contact made by the contact of two of these wool pads is surprisingly good. This method is developed and used by E-systems for stacking MCMs with diamond substrates. 

    
  Figure: (upper) A schematic diagram for an array of contacts between MCMs with through-hole vias. (lower) Two MCMs are stacked by applying a mating force.
  

• Elastomericconnectors with electrical feedthroughs: The vertical interconnections in this method are implemented by a combination of `electrical feedthroughs' and elastomeric connectors. The `electrical feedthroughs' are premanufactured elementsthat are mounted into a laser structured substrate by an embedding technique. A schematic diagram of this method is shown in Figure . This method was developed by the Research Center of Microperipheric Technologies at the Technical University of Berlin. In addition, Texas Instrument has used a variant of this method in the design of a high performance parallel computer called `Aladdin Parallel Processor.'  

    
  Figure: Two wafers stacked using filled vias method.