Fairchild MicroPak™ Daisy Chain Samples
Daisy chain samples are used to verify the integrity of the solder joint between the package and the user's PC board. This is achieved by wiring the daisy chain sample to allow the user to test continuity. Connections for MicroPak daisy chain samples is shown in Figure 1. The daisy chain units and corresponding test boards should be designed to maintain their production thermal and mechanical properties while insuring that any failures will occur at the solder joint rather than elsewhere.
Fairchild daisy chain units have a die attached to match the thermal and mechanical characteristics of production units. Internal daisy chain connections are made by double wire bonds between the substrate pads rather than through bonds to the mounted die (see Figure 2). The double wire bonds made directly to the substrate eliminate wire bond failures as a potential cause of failure during the board level testing.
Wire bond integrity to the die is thoroughly tested by Fairchild during component level qualification testing. In these tests, the temperature cycle qualification was completed with zero failures through 1000 cycles, over -65C to 150C. This MicroPak daisy chain design has been successfully used to validate customer's processes for assembly yield, and the durability of attachment over temperature.
MicroPak Daisy Chain Samples are available through your local Fairchild Sales Office
Figure 1 Board level Pattern for continuity test traces and MicroPak contact pads.
See manufacturing guidlines for suggested dimensions.
Figure 2 Daisy Chain Bonding showing wirebond interconnections and die position within the package.
Double wire bonds go from pad 1 to 2, 3 to 4, and 5 to 6.
