This document discusses pad frame design and packaging for VLSI systems. It covers chip-to-package bonding using gold bond wires to connect pads on the chip to the package. The pad frame distributes signals to the package and helps with cooling. The document provides an example of a MOSIS pad frame layout and discusses generic pad layout considerations. It also covers ESD protection circuits needed on pads to protect from static discharge and provides two examples of pad designs with ESD protection. Finally, it discusses automatically generating a pad frame in Tanner Tools by adding a pad library, modifying the design to use pads, and running the place and route while selecting options to generate the pad frame and route pads.

1. Design and Implementation of VLSI Systems
(EN1600)
Lecture 32: Pad Frame Design and Packaging
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 Diode
clamps
• ESD protection circuits R
PAD
– Current limiting resistor
Current Thin
– Diode clamps limiting
resistor
gate
oxides
– 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
1.Add the pad library to your S-Edit design
2.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
S. Reda EN1600 SP’08 you have these design rules

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