S. Reda EN1600 SP’08

Design and Implementation of VLSI Systems(EN1600)

Lecture 32: Pad Frame Design and Packaging

Prof. Sherief RedaDivision of Engineering, Brown University

Spring 2008

[sources: Weste/Addison Wesley – Tanner Manual]

S. Reda EN1600 SP’08

Packaging choices

S. Reda EN1600 SP’08

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

Pad frame

So far we looked at core designThis lecture we look at pad frame design

S. Reda EN1600 SP’08

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

Generic pad layout

S. Reda EN1600 SP’08

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

PADR

Diodeclamps

Thingate

oxides

Currentlimitingresistor

S. Reda EN1600 SP’08

Example 1: PADARef offers basic ESD protection

Simplest pad

metal 2 distributes VDDmetal 1 distributes signal D

S. Reda EN1600 SP’08

Example 2: PADOUT

Pad has internal buffer

S. Reda EN1600 SP’08

Automatic generation of pad frame in Tanner Tools

1.Add the pad library to your S-Edit design2.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

Automatic generation of pad frame in Tanner Tools

3. In L-Edit, change SPR setup to

Use the new library with the pads and press initialize setup

In padframe setup, Change the layout size to 1.5mm x 1.5mm

In padroute setup, make sure you have these design rules

S. Reda EN1600 SP’08

Automatic generation of pad frame in Tanner ToolsFinally 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