Underfill知识培训-硬盘行业从业经验

Underfill Training Report

ContentFlip Chip Technology Underfill Process Underfill Machine Underfill Epoxy Underfill Failure Mode Analysis Applied Component and Foreground of Underfill

1.Flip Chip Technology1.1 What is flip chip

It is a chip connection technology which interconnects an IC chip to its next level of packaging in such manner that IC’s active side faces to substrate.

Bump P r o c e s s Component

DIE

Substrate

An Integrated Technology!

Adhesive

Substrate

1.Flip Chip Technology1.2 The component-Flip chip

Packaged IC Eutectic Passivation Chip-On-Board UBM

final padDIE

Flip Chip/ CSPSubstrate

Shrinking electronic devices

Flip Chip bump configuration

1.Flip Chip Technology1.3 Flex lamination layer(Cross section)

Dynamic Area Rigid Area Rigid Area

Pad cross-section

Coverlayer/Base Layer Lamination Adhesive 1 Copper Trace Lamination Adhesive 2 Flex structure Stiffener (Metal/Polyimide)

1.Flip Chip Technology1.4 Process Flow

Pre-baking

Solder Printing

Chip Mounting

Bonding

Curing

Underfill X-Ray

Reflow

Cleaning

Function Test

C-SAM(C-mode Scanning Acoustic Microscopy)

Final QC

1.Flip Chip Technology1.5 Why Underfill?Underfill is required to encapsulate under the die to neutralize the effects of CTE mismatch.

Significance: Reduce stress due to thermal expansion Increase lifetime of connections Protect connections mechanically Reduce chance of contamination

1.Flip Chip Technology1.5 Why Underfill?

CTE mismatch of varies components in Flip Chip package will cause high stress at the interconnection. Underfill reduce Stress by distributing such stress over the entire chip area so the stress will not concentrated at the interconnections.

1.Underfill Technology2.1 Relative process flow of underfillReflow Reflow Inspection Pre-heater (In underfill machine)

Touch up

Post-heater (In underfill machine) Curing

Cen-heater (In underfill machine)

Process control point:

Underfill pattern Substrate temperature

Epoxy temperature Curing condition

2.Underfill Technology2.2 Control point in underfill process Underfill pattern selection

2.Underfill Technology2.2 Control point in underfill process Epoxy temperature when dispensingEpoxy’s viscosity profileViscosity

Temp 1

Temp 2

Temp

We select low viscosity temperature to insure epoxy can be dispensed out fluently and flow fast.

2.Underfill Technology2.2 Control point in underfill process Substrate temperature when underfillTemp Reflow 140℃

.

Desired Temperature Profile When Underfill

Temp 1

Reflow Insp

110℃ 95℃

. . . .Temp 2 Pre-heater Cen-heater Temp 3 Temp 4 60sec 30sec 40sec

Temp 5

Time

Dispensing temperature control is let the temperature stable when the pallet in Cenheater(Temp 3 to Temp 5).

2.Underfill Technology2.2 Control point in underfill process Curing conditionNamics U8437-2 epoxy Time of reaction rate X% at each temperature (min.)Reaction rate(%) 5% 50% 90% 99% 99.9% 99.9

9% 99.999% 120 1.1 14.5 18.1 96.1 144.2 192.2 240.3 Temperature( C) 150 170 0.1 0.0 1.1 0.2 3.6 0.8 7.2 1.6 10.8 2.3 14.4 3.1 18.0 3.9o

200 0.0 0.0 0.1 0.2 0.3 0.4 0.5

Insure the reaction rate surpass 99.99% is our control specification.

2.Underfill Technology2.3 Process control in different underfill epoxyItem Epoxy Epoxy Temp Namics U8433L Namics U8437-2 Hysol FP4530 Hysol FP4549 Emerson E-1159 55~65C 50~60C 55~65C/ 30C Substrate Temp 95+5C 85+10C 85+10C 85+10C 50+10C Curing Condition 65C/15mins+150C/60mins 150C/60mins 165C/15mins 165C/30mins 120C/30mins or 130/15mins

3.Underfill Machine3.1 Develop history of dispense valve Air pressure time control

Now we use this for manual underfill Ideal for use in low cost assembly areas Very little maintenance Low cost Dispensed volume changes depending on the fill level of the syringe

3.Underfill Machine3.1 Develop history of dispense valve Auger pump Easy to Clean Used for small dots dispensing of silver/ solder paste and encapsulants Accuracy 3 to 5% typical in the 10 to 100mg range

DV-8K