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Material Aspects of High

Temperature Automotive

Product Packaging

FTF-SDS-F0025

A P R . 2 0 1 4

Tu Anh Tran | C55 Packaging Technical Lead,

Packaging Technology Development

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External Use 1

Session Introduction

• This presentation will provide a review of the challenges imposed

by the high temperature applications in the modern automotive

environment.

• Discuss the changes in packaging materials and processes

required to meet the new requirements.

• Discuss Freescale’s C55FG packaging solution satisfying AEC

Grade 0 packaging reliability requirements.

• Presented by Tu Anh Tran, C55 Packaging Tech Lead, Package

Technology Development.

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Session Objectives

After completing this session you will be able to:

• Understand the landscape of the modern automotive environment

• Compare how new packaging requirements differ from current

requirements in automotive applications

• Describe C55FG LQFP-EP package material and process changes

necessary to meet and exceed the requirements

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Agenda

• New automotive environments

• Implications to packaging

• Challenges and resolutions in:

− Wafer dicing

− Die attaching

− Wire bonding

− Molding

• Session summary

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New Automotive Environments

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Automotive Applications

Advanced Driver Assistance Powertrain Driver Information and

Connectivity Low Cost

Hyper-Integration

Radar Vision Engine & Motor

Control

Advanced

Vehicle

Networking

Instrument

Cluster/

Infotainment

Solution

Integration

Qorivva i.MX Qorivva Qorivva i.MX S12 MagniV

Advanced safety

MCU’s with

integrated high-

performance analog

and DSP

Multicore Cortex

MCU’s with image

processing by

Quad-core safety

MCUs with advanced

timer and

instrumentation

systems

Advanced MCU with

integrated hardware

security for high-

performance vehicle

connectivity

Multicore Cortex

MCU’s with advanced

multimedia features

and extensive OS

support

Total system solutions

MCU with analog and

power integration for

easy solution

development.

Ethernet

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More Challenging Powertrain Applications

Junction

Temperature (C)

Duration

(hours)

150 50

145 150

135 1,200

120 4,600

Total 6,000

Junction

Temperature (C)

Duration

(hours)

150 3,000

130 10,000

110 7,000

Total 20,000

Previous Under the Hood

Application Profile

New Under the Hood

Application Profile

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Implications to Packaging

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Reaching for a Higher Packaging Certification Level

Certify next-generation multicore automotive controller C55FG

packages (LQFP, MAPBGA and TE-PBGA) to AEC Grade 0

requirements, 2X AEC Grade 1.

Package Stress AEC Grade 1 AEC Grade 0 Responses

Air-to-air Temperature Cycling

AATC (-50/150ºC)

1000 cycles 2000 cycles • Electrical test

• Decap / wire pull

and ball shear

• Package

interfacial delam

inspection

High Temp Bake HTB-150ºC 1000 hours 2000 hours

High Temp Bake HTB-175ºC 500 hours 1000 hours

Unbiased HAST-110ºC 264 hours

Biased HAST-110ºC or THB

(85ºC / 85%RH)

264 hour HAST or

1008 hour THB

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More Stringent Requirements for LQFP-EP Packaging

LQFP-EP Cross Section

A B

C

D E

A

Wire

B

Copper Leadframe C

Die Attach

Silicon Die

Epoxy Mold Compound

D

E

Packaging Materials Specific Challenges for AEC Grade 0

Delamination resistance in temperature cycling

60um scribe dicing capability

Ball bond reliability in temp cycling and high temp bake

Die surface delamination resistance in temperature cycling

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Wafer Dicing

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Dicing Process Development

• Objective: Develop mechanical

dicing process for 60um scribe width

• Process variables:

− Blade selection

− Dicing process parameters

− Die seal ring design

• Key responses:

‒ Top side ILD peeling

‒ Top side chipping

‒ Back side chipping

‒ Die sidewall scratch

‒ Blade wear rate

‒ Electrical test

Non Low-k C90/C55

Seal R

ing

Ad

hesio

n S

tren

gth

(J/m

2)

FSL die seal ring is 67% stronger

than pre-C90 nodes

Scribe width: 60um

Dicing width

Top Down View of Wafer Scribe

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Results of Key Dicing Responses

60um dicing

process

successfully

developed and

deployed across

Freescale

internal factories.

Sidewall Inspection

Scratch Free

Backside Chipping Depth

Blade 1 Blade 2 Blade 3

Z2 Blade

ILD Peeling Top Side Chipping

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Test Vehicle (TV) Enables Robust Dicing Defect Detection

Electrical Crack Detect (ECD)

‒ Vertical serpentine around die

‒ Tabs connected to pads to isolate

defect segment

Corner Delamination Sensor

‒ Vertical serpentine at die corners

‒ Each metal layer connected to a pad

to isolate delamination layer

Dicing Test Structures Metal Box Density DOE

Metal Line Density DOE

Test Vehicle

6.5 x 6.5mm

55nm 6M1T

Functional I/O cell

Stack-up View of ECD

Stack-up View of Corner Delamination Sensor

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Die Attaching

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Die Attach Interfacial Delamination Resistance

• Objective: Select die attach

adhesive for LQFP-EP based on

manufacturability, interfacial

bond and reliability

• Key responses:

‒ Interfacial strength characterization

‒ Delamination inspection after

package reliability stresses

‒ Delamination inspection after

board mounting

LQFP-EP 2000 Cycle AATC

(-50/150°C)

Standard Die Attach

CSAM detected

75% die attach

delamination

underneath die

Fracture in

Die Attach

Die

Exposed Pad / Die Flag

Interfacial

Delamination

Cross Sectional Views

Die flag

delamination

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Die Attach Interfacial Strength Characterization

New die

attach

adhesive

has greater

adhesion

strength.

Stud-Pull Tensile Testing

Stud-Pull Failure Inspection

Sta

nd

ard

Die

Att

ac

h

New

Die

Att

ac

h

Die Die Die Attach

Standard Die Attach New Die Attach

Finer Ag

filled

Stud-Pull Tensile Test Results

Standard New

Die Attach Die Attach

Interface

Failure

Cohesive

Failure

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New Die Attach +

Thinner Die +

Further Design

Improvement

0% 3% 0%

New Die Attach +

Thinner Die 10% 50% 0%

New

Die Attach 15% 70% 0%

Non-

delaminated

region

Die Attach Delamination Performance in LQFP-EP

AATC (-50/150°C)

2000 Cycles 4000 Cycles

Certification Readpoints Extended Readpoints

1000 Cycles

New die attach, optimized die / package structure and package design

improvement produce consistent resistance to delamination in Temperature

Cycling, meeting AEC Grade 0.

Current

Die Attach 100% 13% 75%

Delaminated

region

Die Attach Delamination Criteria: > 30% die area

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Die Attach Delamination Performance at Board Level

Reliability Test (-40/125°C)

T0 Final Readpoint 5794 Cycles

Die to Flag (Die Attach) Interface Scan

Very robust reliability and high interfacial strength (no delamination)

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Wire Bonding

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High Reliability Wire Bond Interconnect

• Objective: Select wire type and develop

wire bond process for AEC Grade 0

− Freescale selected Pd-Cu wire on Al

interconnect

• Key responses:

‒ Electrical tests after package reliability

stresses

‒ Wire pull strength after High Temperature

Bake (HTB) and Temperature Cycling (TC)

‒ Ball shear strength after High Temperature

Bake and Temperature Cycling

‒ Cu-Al intermetallic compound (IMC) growth

characterization

Al Pad

Au

Wire

Cu

Wire

Pd-Cu

Wire

Al Pad + Ni / Pd / (Au)

Over Pad Metallization

Au

Wire

Cu

Wire

Pd-Cu

Wire

Wire Bond Interconnect Options

Au Wire on Al Pad - 1008hr HTB-175°C

Excessive IMC growth leading to

Kirkendall voiding and electrical failure

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Optimizing Pd Coverage for Pd-Cu Ball Bonds

Pd Coverage on Free Air Balls (FAB) vs.

EFO Current for 3 Pd-Cu Wire Types

Pd Coverage on Etched Ball Bonds vs.

EFO Current for 3 Pd-Cu Wire Types

Pd-Cu wire B has best Pd coverage and widest EFO current window.

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Extensive Cu Wire Bond Characterization

• Performance attributes:

− Ball bond diameter

− Ball bond height

− Ball bond formation and placement accuracy

− Aluminum push-out

− Aluminum remnant

− Intermetallic coverage

− Wire loop height

− Ball shear strength on strip-level

− Wire pull strength on strip-level

− Second bond width

− Second bond placement

− Wire peel strength

− Cratering test

• Process parameters:

− Process definition and RSM Optimization

− Process windowing

Digitized Image of IMC Coverage Example: 93%

No Damage to Barrier Layer after Ball

and Al Pad Removal (Cratering Test)

Cu Ball Formation

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Achieving No Wire-Pull Ball-Lift Failures after HTB

• Ball lift after decap / wire pull at 1000 hour HTB-175°C observed on bare Cu but NOT on Pd-Cu wire on Al pad.

• Hairline crack above Al-rich IMC found with bare Cu wire caused ball lift.

• Pd-Cu wire designed to regress IMC formation.

Cu Wire on Al at 1000 HTB-175°C

Pd-Cu Wire on Al at 1000 HTB-175°C

Cu Ball

Pd-Cu Ball

Intermetallic Formation Reaction Rate K (cm2/sec)

Temperature

(150°C)

Au - Al 110 X 10-16

Cu - Al 3.18 X 10-16

PdCu - Al 2.89 X 10-16

Ball Lift

Hairline crack

above IMC

Cu-Al IMC

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Achieving No Wire-Pull Ball-Lift Failures after Temp

Cycling

• Ball lift after decap / wire pull at 2000

AATC cycles observed on both bare

Cu and Pd-Cu wires on Al pad.

• Crack in Al pad caused ball lift

during wire pull.

• Assembly process optimized to

eliminate ball lift issue after

Temperature Cycling.

Cohesive Crack in Al

2000 Cycles of Temperature Cycling

Ball Lift

Al and underlying layer

Pd-Cu Ball

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Exceeding AEC Grade 0 Requirement

Passed electrical test at 2X AEC Grade 0.

Passed decap / wire pull and ball shear at 2X AEC Grade 0 with

no ball lifts.

Ball Shear (gf) Wire Pull (gf)

LSL = 1.8gf for 20um wire LSL = 9gf for 43um ball diameter

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Molding

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Epoxy Mold Compound for AEC Grade 0

• Objective: Select an epoxy mold

compound for LQFP-EP / LQFP

packages for manufacturability,

passivation die top interfacial bond

at AEC Grade 0 reliability.

• Key responses:

‒ Electrical tests after package

reliability stresses

‒ Delamination inspection after

package reliability stresses

LQFP-EP

2000 AATC Cycles

(-50/150°C)

Standard Epoxy Mold Compound

200µm

200um delamination between mold

compound and passivation die top surface

Die Top (C3)

Delamination

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Higher Stress at Die Corner 3

Silica filler loss opposite the mold gate entrance at passivation die

top corner (C3) has higher stress causing interfacial delamination

under cyclical loads.

Die Corner 3 (C3) Die Corner 1 (C1)

Filler loss

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Current

Mold Compound

Optimized

Die/Pkg Structure +

Process Changes +

Mold Compound

Die Top Interfacial Delamination Resistance Results

AATC (-50/150°C)

Certification Readpoints - 2000 cycles Extended Readpoints – 4000 cycles

Optimized die/package structure, mold process and new mold compound

produce consistent resistance to “passivation die top” delamination during

AEC Grade 0 temperature cycling across several LQFP/LQFP-EP products.

100%

> 200 µm

delamination

100%

>160 µm

delamination

0%

No

delamination several products

1%

~60µm

delamination

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Summary

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Session Summary

• Modern automotive environments impose new application profiles

at higher temperature and longer duration.

• The requirement for next-generation powertrain product packaging

is AEC Grade 0 which is 2X the current requirement.

• Freescale LQFP-EP package is a cost-effective solution meeting

and exceeding the challenging AEC Grade 0 packaging reliability

requirement.

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For Further Information

• SME Contact information

− Tu Anh Tran, C55 Packaging Technical Lead

− Tu.Anh.Tran@freescale.com

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© 2014 Freescale Semiconductor, Inc. | External Use

www.Freescale.com