For those who are not familiar with terminology

What is DST? (back to top)

Direct Stacking Technology is an innovative memory stacking solution that simplify both the stacking design and the manufacturing process. Previous memory stacking techniques involve the use of additional materials such as a lead frame or PCBs. However, Direct Stacking Technology requires no supporting materials. This translates into a staking design that requires far fewer solder joints. Compared to the "Indirect stacking" , Direct Stacking Technology requires about 1,200 fewer solder joint and this substantial reduction in the number of solder joints required per stack enables Direct Stacking Technology to achieve reduced manufacturing time, higher yield, greater reliability, and reduced cost per manufactured item. The following table shows the side by side comparison between Direct Stacking Technology from POLYSTAK and "Indirect Stacking Technology" from competitor's.

DST(Direct Stacking)
IST (Indirect Stacking)
99% guaranteed
Added Materials
Copper alloy layer
Visual Inspection
Okay, but metal leads block the sight in certain angle
Better than a single TSOP (leads have a very thin coat of solder after the assembly process)
Almost the same as a single TSOP
Number of Solder Joints
Per Lead
Per Stack
18 Stacks on Module

2,376 *

Module Reparability
Using Stacked Parts
Easy (Same repair equipment and techniques as used for single TSOPs)
Same as a single TSOP
Almost the same as a single TSOP
Frequency Response
Same as original single TSOP
Less than original single TSOP (reduced by copper alloy lead parasitics)
Changes in Mechanical
Dimension after Stacking
Almost None
Metal layer cause an increment in height
Cross Sectional View


What is CSP? (back to top)

What is SiP ? (back to top)


What is Flip Chip? (back to top)


What is SoC? (back to top)


What is wafer bumping? (back to top)


How silicon chip is made? (back to top)


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