1. Design and Implementation of VLSI Systems (EN1600)
Lecture 32: Pad Frame Design and Packaging
Prof. Sherief Reda
Division of Engineering, Brown University
Spring 2008
[sources: Weste/Addison Wesley – Tanner Manual]
S. Reda EN1600 SP’08

2. Packaging choices
S. Reda EN1600 SP’08

3. Chip-to-Package Bonding
Traditionally, chip is surrounded by pad frame
Metal pads on 100 – 200 mm pitch
Gold bond wires attach pads to package
Lead frame distributes signals in package
Metal heat spreader helps with cooling
S. Reda EN1600 SP’08

4. Pad frame So far we looked at core design
This lecture we look at pad frame design
S. Reda EN1600 SP’08

5. MOSIS AMI 0.5u Tiny Chip frame
Tanner reserves one of the left pins for VDD and one of right pins for GND
S. Reda EN1600 SP’08

6. Generic pad layout
S. Reda EN1600 SP’08

7. ESD protection Static electricity builds up on your body
Shock delivered to a chip can fry thin gates
Must dissipate this energy in protection circuits before it reaches the gates
ESD protection circuits
Current limiting resistor
Diode clamps
Diodes must be large to sustain significant current
Example: Consider charge on human body discharged at a rate (current) = 10 uA for 1us at to a capacitor C=0.025pF → Voltage buildup = 400V destroys the transistor gate
S. Reda EN1600 SP’08

8. Example 1: PADARef offers basic ESD protection
metal 2 distributes VDD
metal 1 distributes signal D
Simplest pad
S. Reda EN1600 SP’08

9. Example 2: PADOUT
Pad has internal buffer
S. Reda EN1600 SP’08

10. Automatic generation of pad frame in Tanner Tools
Add the pad library to your S-Edit design
Modify your design to use the pads.
Naming convention: if you name nets getting into a pad as PAD_L1 places the pad at the first left location in the pad frame.
S. Reda EN1600 SP’08

11. Automatic generation of pad frame in Tanner Tools
3. In L-Edit, change SPR setup to
In padframe setup, Change the layout size to 1.5mm x 1.5mm
Use the new library with the pads and press initialize setup
In padroute setup, make sure you have these design rules
S. Reda EN1600 SP’08

12. Automatic generation of pad frame in Tanner Tools
Finally run the place and route and make sure to mark “PadFrame generation” and “Pad route”
You might get a few DRC violations in metal2 that you would need to fix yourself
S. Reda EN1600 SP’08