What’s Mirco SMDxt?
Micro SMDxt or USMDXT, are the abbreviations of Micro Surface-mount Device Extended Technology, which is a wafer level chip scale package (WLCSP) (or we call it as a DSBGA) with the following features:
- Package size equal to die size
- Smallest footprint per I/O count
- No need for underfill material
- Interconnect layout available in 0.4 mm or 0.5 mm pitch
- No interposer between the silicon IC and the printed circuit board (PCB)
Micro SMDxt (USMDXT)
| Package Arrays | |
| Bump Count | Array Outlines |
| 36 | 6x6mm |
| 42 | 6x7mm |
| 49 | 7x7mm |
| 56 | 7x8mm |
| 64 | 8x8mm |
| 80 | 8x10mm |
| 81 | 9x9mm |
| 100 | 10x10mm |
| Bump Size Details | |
| Bump Diameter | 0.265mm, 0.320mm |
| Pitch | 0.4mm, 0.5mm |
| Bump Count Range | 36-100 |
| Bump Thickness Nominal | 0.65mm |
| Bump Height Nominal | 0.255mm, 0.210mm |
| Bump Copalarity within Package | 0.015mm |
| Shipping Method | Tape and Reel |
| Moisture Sensitivity Level | Level 1 |
Micro SMDxt SMT Assembly Considerations
SMT assembly operations include:
- Printing solder paste on PCB.
- Component placement using standard pick and place equipment.
- Solder reflow and cleaning (depending on flux type)
Advantage during SMT assembly include:
- Standard tape and reel shipping media eases handling issues (per EIA-481-1)
- Uses standard SMT pick and place equipment
- Standard reflow process
Component Placement
Standard pick-and-place machines can be used for placing the micro SMDxt. Either of the following
methods can be used for recognition and positioning:
- Vision system to locate package silhouette
- Vision system to locate individual bumps. It is recommended that the side-lighting option on the pick and place machine’s vision system be used when attempting to use a individual bump recognition approach to ensure better contrast for bump recognition.
Other features of micro SMDxt placement are as follows:
- It is preferable to use IC placement/fine pitch placement machines instead of chip-shooters for better accuracy.
- Although micro SMDxt can withstand a placement force of up to 1 kg for 0.5 seconds, little or no force needs to be exerted during placement. It is recommended that bumps be dipped into the printed solder paste to greater than 20% of paste block height.