Optoelectronics Packaging Research 2001

1

Optoelectronics Packaging Research 2001

Peter Borgesen

2

Optoelectronics Packaging Research

Long term:Contribute to transition from low volume, partiallymanual and robot based assembly of ‘pieces’ tofully automated manufacturing like microelectronics.

Requires combination of:design for manufacturing & qualitymaterials development & characterizationsystems & equipment developmentprocess development

Obviously won’t (can’t) do all this, but to contribute we must understand: Research and education.

3

Research & Education

Research: Establish activities in ‘1st-3rd‘ level packaging Understand current practices Problem solving with/for manufacturers Research topics of generic, long term relevance to automated manufacturing

Education:Relevant research experience for our studentsWork with university on manufacturing relevant curriculum4 hour tutorial on basics of optoelectronics packaging

4

1st-3rd Level Packaging

Optical Sub Assembly (OSA):Rotator, polarizer, birefringent crystalsLaser attach

Component assembly:TEC attachOSA attach

Fiber: Handling & ReliabilityPigtailing & Connectorization

Component attachment:AdhesiveSelective soldering?

5

Quality & Yields

Initial impressions:

Interesting combinations of high precision (active alignment) and manual or semi-manual assembly common.

Reproducibility: Only know quality of part tested?

Yields?

6

Welding ring

SM Fiber

Isolator

Lens holderAspherical lens

Sleeve

22mm

5.6m

m

Laser

Not exactly designed for manufacturing

Simultaneous active alignment along 6 axes: Lens holder in X, Y (for lens) and (isolator) Fiber sleeve X, Y, Z

Coaxial Laser Module

7

Generic 10Gbps Laser Module

AlN

OSA

monitor diode onceramic

filter

lens

laser onceramic

lenses

isolator

modulatoron ceramic

TECSELFOClens

Nor is this one !

8

Laser Diode Packaging

Not all packages are that complicated.

In it’s simplest form a laser diode package has a laser shooting into fiber

The rest is a matter of optimizing performance and (too rarely) ‘manufacturability’

9

Edge Emitting Laser

1-3 gold wire bonds to same electrode

electrical contact to substrate

10

Edge emitting laser attached to prototyping substrate with In solder, and lensed fiber with Ruby ring

laser

solder

wire bond

lensedfiber

Edge Emitting Laser Attach

11UV tack adhesive

Ruby ring

fiber sleeve

lasersubmount

TEC

ceramic‘optical bench’

butterfly package

Prototype Laser Diode Package Very similar looking product still offered commercially

12

Optimizing Performance

AlN

OSA

monitor diode onceramic

filter

lens

laser onceramic

lenses

isolator

modulatoron ceramic

TECSELFOClens

Parts all help optimize, but we still have choices to make: Package details (sealing), order of assembly & alignment. Free space/waveguides/lensed fiber/SSC (alignm. budget)?

Free space coupling to selfoc and fiber

13

Coupling of Edge Emitting Laser

Modes are not well matched: Different sizes/divergencies Optimized butt coupling to cleaved SM fiber offers only 9% efficiency

14

SM Laser - Fiber Coupling

Mode Field Diameter (MFD): 1/e2 width, typically 15% larger than core

Mode field mismatch loss (perfect alignment):

2fiberMFD2

laser,yMFD

fiberMFDlaser,yMFD

2fiberMFD2

laser,xMFD

fiberMFDlaser,xMFDlogdBP

2210

Effects of misalignment also depend on mode field diameters and match!

15

Coupling of Edge Emitting Laser

Greatly improved by insertion of lens(es), but at the expense of reduced alignment tolerances.

16

Optical Aligment

Consider transverse misalignment (x,y) only. Thenexcess (butt-)coupling loss

2fiberMFD2

ylaser,MFD

2y

2fiberMFD2

xlaser,MFD

2x

excP 44

20

In a sense lens may be viewed as increasing MFDlaser,x/y at the fiber surface, reducing sensitivity to x/y there reducing MFDfiber at the laser surface, increasing sensitivity to x/y there

Laser-lens alignment in x-y now less tolerant.

17

Optical Aligment

Angular alignment tolerance clearly depends on transverse and longitudinal misalignment.

If both the latter are zero, loss contribution varies with

So, expansion of either mode increases sensitivity toangular misalignment at location in question

2fiberMFD2

laserMFD

1)(sin

1

2

18

Lensed Fibers

Kyocera

Lensed fiber offers >90% coupling efficiency, but is very expensive and reduces alignment tolerance

19

Combine with GRIN lens: >90% Expensive, 0.2m alignment

Single aspheric lens may offer 55% coupling efficiency

Lenses

GRIN: Parabolical variation in n(r), flat surfaces

20

Ball Lenses

Ball lenses are clearly less effective than aspheric and, in particular, GRIN lenses. However, they are cheaper and easy to use

21

Optical Aligment

Alignment of fiber and/or lens to within 0.1-0.2m often required for 85-95% SM coupling.

About 50% often achievable with 1m.

Fiber variations (diameter, core concentricity, cladding elliptricity) seem to prohibit passive alignment to better than 1m.

22

Blumenthal, UCSB

Spot-size converter (in/at waveguide, amplifier, coupler, ...) may improve coupling (mode matching).

Laser spot conversion raises lateral & longitudinal alignment tolerances (reduces angular tolerances).

Spot Size Conversion

23

Optical Aligment Expanding 0.3m laser spot to 1-2m before emission may raise tolerances to more than 1m.

-3 -2 -1 0 1 2 3 Position (m)

0

-2

-4

-6

-8Cou

plin

g E

ffici

ency

(dB

)

Regular laser

w. spot-size converter

0.75m

1.4m

Fish et al., UCSB

24

‘Classical’ butterfly package design is not equally suitable to all coupling schemes:

Fiber manipulation through hole in wall unnecessarily ackward

Optimize/improve Manufacturability

25

Generic 10Gbps Laser Module

Real products may use adhesives or AuSn solder & welding. Overall assembly issues very sensitive to choice.

Sensitivity to warpage/creep depends on alignment/coupling scheme (often not considered in design).

26

Optical Bench Structure in Cooling

Silicon or ceramic bench:

Always CTE mismatches

Almost always warpage

FEM: ‘Typical’ structures may warp 0.2-0.4m/oC Sensitive to adhesive properties, but always significant (Plastic) creep properties important.

27

Typical components include laser, monitor, modulator, lens, isolator, pigtail, filter, detector, amplifier, cooler, driver chip

Laser Diode Package Contents

Let’s consider optical isolators: ‘Optical diodes’

28

Reflections

‘External cavity’ may create extra modes in SM laser. -30dB (0.1%) reflection may destabilize laser

29

Polarization Sensitive Optical Isolator

Po

larc

or

Po

larc

or

Ro

tato

r

Faraday rotator: Non-reciprocal rotation of polarized light

intensity

polarization

30

Polarization Sensitive Optical Isolator

Magnet

31

Polarization Insensitive Isolator

Also developing polarization insensitive isolator and circulator.

Separate components, just keep adhesive from optical path.

Current (manual) practice showed obvious manufacturing issues:

Quality/yields? Automatability?

32

Polarization Insensitive Optical Isolator

Primary light transmission

33

Isolator

GRIN lensGRIN lens

Primary light focussed to minimum spot by GRIN lens. Exit beam focussed back into same fiber from 16m spread


34


Deflection of backward light: Divergent beams not focussed back into upstream fiber.

35

adhesive

View of interface between rotator and wedge


Wedge/rotator/wedge sandwiches each glued together along edges. Minute gaps left by surface morphologies: Capillary action.

Uncontrollable

1m

mAt a minimum optical path must be epoxy free

36

Wideband Polarization Insensitive Isolator

Optical isolator assembly with epoxy: Very small parts, awkward locations, lots of active alignment.

37

coatedfiber

ferrule

cylinder

epoxy


Pigtail prepared by inserting stripped into epoxy in ferrule. Ferrule epoxied into steel cylinder.

38

GRIN lens epoxied into other end of steel cylinder

GRIN

AR coating

epoxy


39

GRIN lens inserted into magnet and gap to cylinder filled with epoxy.

magnet

GRIN

8o

fiberferrule

cylinder


40

Another GRIN lens actively aligned with exit side

magnet

GRIN lens


41

Steel cylinder with GRIN lens and fiber ferrule (at other end) soldered to outside cylinder


42

Isolator

GRIN lens

GRIN lens

Remember offset? But this manufacturer did not botheroffsetting fiber opening at end of cylinder.

End segment tilted, fiber bent to 1” radius. Uncontrolled!How well is stripped section protected from bending?(1/10 stripped fibers bent to 1” would last 11 days at 50%R.H.)


212m

43

Adhesives offer some obvious attractions for automation.

However, dispensing is a bit of an art form.

Also, there are numerous issues with properties.

Adhesives

44

Adhesive Projects Importance of deposition process control:

FEM

Dipping, pin transfer and dispense of small volumes: Fundamentals and applied.

Shifts in placement and cure: Effects of deposition control & materials properties

(just started)

Gap & constraint dependent cure kinetics & properties:Realistic configurations vs. DSC, DMA & data sheets

Creep & misalignment:FEM & experiments (to come)

45

Effect of temperature change on optical component with asymmetric adhesive fillets: Rotate 1o per oK !

Adhesive Deposition Process Control

46

Magnet opening w. isolator structure adhesive


Small adhesive volumes in awkward locations

47

AdhesiveTO-can

Fiber

Adhesive Fixturing of TO-can

Small adhesive volumes in awkward locations, uniformity critical

48

0.25mm

How small is small volume? This ball lens needs 1g of adhesive in small dot: wet-out important?

Small Adhesive Volumes

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Auadhesive

Flip Chip VCSEL by Dipping

Alternative small volume application

50

Auadhesive

Flip Chip VCSEL by Dipping

Alternative small volume application

51

Dipping, dispensing, or pin transfer preferred depending on volume & location control needed.

Automation requires minimization of scatter.

All dominated by dynamic wetting.

Adhesive Deposition

52

1a) 1b) 2)

3a) 3b)

The 3 Stages of Dipping

1) Insertion2) Hold3) Withdrawal

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insertionwithdrawal

Speed

Dynamic Liquid-Solid Contact Angle

Steady-state wetting

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Dynamic Liquid-Solid Contact

Similar picture applies to pin transfer deposition step.

Dispensing of dot may be viewed as transfer with hollow pin, in some respects.

Steady-state contact angle scales with

and slow model pin transfer experiments could be rationalized on basis of steady-state:

More pick-up with faster withdrawal, etc.

lvvμ

Ca

55

Realistic applications may not reach steady-state in each step:

Much faster withdrawal (and no hold) shortened time in adhesive, and thus time to reduce contact angle, giving less pick-up.

The time to approach steady-state to a certain extent should scale with

Short travel distance (dip depth) and high speed may define other ‘simple regime’ for flip chip dipping (dependence on hold time?).

Otherwise, dynamics can be calculated numerically and calibrated experimentally:

Minimize sensitivity to variations (scatter).

ot

μCb

lv

Dynamic Liquid-Solid Contact

56

Pin Transfer

Adhesive dots on glass surface

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Pin Transfer

Process far from optimized yet, but 1g dots deposited with

diameter=1%

volume=2%

Strong sensitivity to substrate chemistry and morphology:

Account for latter in choice of transfer height

58

Initial studies considered four UV/blue light curable adhesives

Supplier indicates ‘seconds’ of light or 1 hour at 100oC (or 2 at 80oC), but suggests testing for performance.

Careful: Shadowing may affect curing (need post cure) and formation of protective skin against oxygen inhibition of post cure.

There are also other reasons for cure kinetics and properties to depend on configuration.

Sometimes DSC data only qualitatively relevant

Cure and Properties of Optical Adhesives

59

DSC of Optical Adhesives

Effect of duration of thermal cure at 100oC from subsequent DSC scans. Cure-% is defined as relative peak area.

60

AdhesiveTO-can

Fiber

Thin, Constrained Adhesive Layers

Cure kinetics and resulting properties unlikely to be the same as in ‘bulk’.

61

Silicon V-grooves for optical fiber array: 0-90m adhesive

Thin, Constrained Adhesive Layers

62

Exposure to light from both sides (max. depth 0.75mm) Avoid shadowing.

Take shear strength as measure of cure.

1.5mm.125mmadhesive

Adhesives in Realistic Configurations

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75

80

85

90

95

100

0 100 200 300 400

Light (sec/inch sq.)

Cu

re %

DSC of A146T After Light Cure

Light/distance2 (sec/inch2)

% c

ure

Apparently no further curing above 120s

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0

5

10

15

20

25

30

0 50 100 150 200

Time of light cure (sec)

Bre

akin

g S

tren

gth

(lb

f)

Shear Testing of A146T After Light Cure

0 2x50 2x100 2x150 2x200


30

20

10

0

Str

eng

th (

lbf)

However, there is clear increase in strength after more light

65

75

80

85

90

95

100

0 1000 2000 3000 4000 5000 6000sec/inch sq.

% C

ure

no thermal

+1hr @100C

+1hr @115C+1hr @110C

DSC of A146T After Light + Thermal Cure


% c

ure

Also, more light enhances efficiency of subsequent thermal cure

66

A146T Effect of Light

What’s ‘fully cured’?

According to DSC we need lots of light:

1.5hours @ 1” distance + 1hour @ 115oC for ‘complete’ 0.5-1.0hours @ 1” + 1hour @ 110oC for 99% cure

Interpretation:

>60s needed on each side to create reproducible‘skin’ against oxygen inhibition (see next).

Still need to see how much is ‘enough’ cure.

67

-4

-3

-2

-1

0

1

2

0 0.5 1 1.5 2

0.99

0.9

0.5

0.2

0.1

0.05

0.02 1 2 3 4 5 6 7 Strength (MPa)

Fai

lure

Pro

babi

lity

30 min

45 min

A146T: Effect of Thermal Cure After 2x60s Light

Broad statistical distributions of strength

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-4

-3

-2

-1

0

1

2

0 0.5 1 1.5 2 2.5

0.99

0.9

0.5

0.2

0.1

0.05

0.02 1 2 3 4 5 6 7 8 9 10Strength (MPa)

Fai

lure

Pro

babi

lity

45 min

60 min

A146T: Effect of Thermal Cure After 2x60s Light

Broad statistical distributions of strength

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-4

-3

-2

-1

0

1

2

0 0.5 1 1.5 2 2.5

0.99

0.9

0.5

0.2

0.1

0.05

0.02 1 2 3 4 5 6 7 8 9 10Strength (MPa)

Fai

lure

Pro

babi

lity

2x60s

2x180s

A146T: 1 Hour Thermal Cure After Light

3min on each side enough for reproducible ‘skin’?

70

Effects of shadowing and dimensions (thickness & depth)

1-11mm.01-.4mmadhesive

Adhesives in Long, Narrow Gaps

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Effect of Depth (Bond Length)

Ultimate shear strength should be proportional to bond area (shear stress should be independent of bond length).

Initial increase could be oxygen inhibition?

A4061T1 hour thermal cureNo light.

72

Effect of Thermal Cure Ambient (A4061T)

Slower thermal cure in air (oxygen inhibition?)

Much slower cure in closed DSC pan: Effect of configuration?

73

Effect of Light on Thermal Cure (A4061T)

Light builds protective ‘skin’: Most important at shallow depths.

Still doesn’t explain ultimate stress dropping with bond length!

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0

500

1000

1500

0 5 10 15 20

Effect of Thickness (A4061T)

Gap Size (mil)

Str

en

gth

Light exposure + 1 hour thermal (in vacuum)

Of greater concern: Abrupt dependence on thickness(without change in failure mode).

75

Optical Adhesives Cure-% measured with DSC not directly useful.

We wouldn’t know which % is ‘enough’, even if it applied to configuration of concern.

Cure kinetics and properties vary in complex fashion with configuration.

Some of this may be ascribed to ‘shadowing’ of light and the formation of a protective ‘skin’ on the surface.

However, systematic variations with bond length and thickness were not.

76

Fluxless Au-Sn Soldering

‘Standard’ in hermetic applications

Void less laser attach Feedthrough

Attach sub-mm pieces in tight spaces

77

Maintain alignment: creeps less than epoxies and soft solders no swelling or densification

Hermeticity: outgasses less than epoxies (and even Sn/Pb)

AuSn

78

Cooling & temperature stabilization: better thermal conductivity than filled epoxies and alternative hard solders

Voids easily affect laser temperature control.

Laser Attach with AuSn

79

Process usually must be fluxless.

Current approaches involve

N2(5-10%H2) atmosphere

scrubbing

static pressure?

pressure variation & vacuum

AuSn Soldering Process

80

Current approaches are not attractive for true volume manufacturing.

Scrubbing breaks up surface films but may supposedly disturb molten solution and reduce homogeneity.

Soldering in N2 (without H2) possible, but may enhance risk of voiding:

Sn goes to surface of liquid, but H2 scavenges O2

Also works in vacuumH2 less important if interface not exposed in melt?


81

AuSn Soldering With Preforms

Don’t entrap voids:

Don’t touch/damage ‘bottom’ of preform before placement.

Don’t let contact pad touch top of solid preform: Heat before place enhances throughput too Sn on liquid surface exposed to ambient!

82

AuSn Soldering From Multilayer

Au/Sn/Au thin film structure may allow pad contact (protection of interface) before melt.

Also allows for patterning of small contact areas (see isolator).

No oxide layer before reflow.

Design structure for stability ‘on shelf’ and bonding before ‘freezing’.

Small thickness should help reflow hierarchy?

83Massalski, 1990

Au-Sn Phase Diagram

84

Sn

Au

Au

Au

Adhesion layer

Adhesion layer


As deposited

Polarcor (borosilicate glass)

Rotator (thin film garnet crystal)

85

AuSn

Adhesion layer

Adhesion layerAu

Au

Au




After aging at RT?

Sn is still protected from ambient !

86

Adhesion layer

Adhesion layerAu

Au

Au71Sn29




After reflow

Still enough Sn to mix with Au on rotator pad

87

Sn

Au

Au

Au

Adhesion layer


As deposited



Au

Au

Sn

Ni

Adhesion layerNi

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Soldering With Predeposited AuSn Alloy

Shares some advantages with multilayers, but

less protection against oxidation before reflow

does not require as careful design of thicknesses

Eutectic or Au-poor?

At least one supplier suggests reflow in air!?

Currently under investigation.

89

Au at-%Sn

Revised, Ciulik & Notis

Mechanical properties depend on ?

Effects of reflow parameters on creep TBD


90

Fibers are bent, squeezed, pulled, cleaved, stripped, cleaned, spliced, connectorized, polished

Invariably mounted under thermal mismatch stress.

Optical Fiber Handling & Reliability

91

Optical Fiber Projects

Quantify importance of damage in handling and packaging:

Predict ‘life in service’ -- effects of load, humidity, damage

Quantify damage

Identify non-damaging procedures

92

Optical Fiber Handling & Reliability

Fibers may fail (apparently) instantaneously under sufficiently high load. You’ll notice that.

Fibers may fail more gradually (minutes, hours, days, years) by subcritical growth of a surface defect. That’s scarier.

The former is easy to test for.

How do we test for the latter?

93

Optical Fiber Damage & FailureAn optical fiber breaks when

KI >KIc=0.75MPa*m1/2

where

at a surface defect of length a.

The only significant sub-critical crack growth is caused by a chemical reaction with water.

This is only significant if the effective activation energy is reduced by a tensile stress. If so, even an extremely low humidity level (hermetic package) may be sufficient.

aYK I

94

1.E-07

1.E-05

1.E-03

1.E-01

-0.4 -0.35 -0.3 -0.25 -0.2 -0.15 -0.1

Cra

ck V

elo

city

(m

/s)

Stress Intensity Factor (MPam)

0.4 0.5 0.6 0.7 0.8

critical crackgrowth

moisturediffusionlimited

stress &humiditylimited

Crack Growth Rate vs. KI

10-1

10-3

10-5

10-7

By the time we reach diffusion limited regime it’s essentially over!

95

Life & Damage Assessment

Industry test data are most often interpreted based on a power law for sub-critical crack growth:

This may overestimate service life by several orders of magnitude (years vs. days).

We and others find best agreement with

nIKA

t

a

Im

%R.H.I epAt

a

96

Based on dynamic strength measurements at moderate and high loading rates literature agrees on p 2 in

but we find p to increase with decreasing loading rate:

p 2 at 25-1000lbf/min

p 4 at 0.5lbf/min

p 4 under static load

Life & Damage Assessment: Humidity

Im

%R.H.I epAt

a

97

14

15

16

17

18

19

0 20 40 60

Dynamic tensile strength of pristine fiber at 1000lbf/min

AI (%R.H.)2

AI (%R.H.)4

Str

en

gth

(lb

f)

Humidity (%R.H.)


98

12

13

14

15

16

17

0 20 40 60 80

AI (%R.H.)4

AI (%R.H.)2

Str

en

gth

(lb

f)

Humidity (%R.H.)

Dynamic tensile strength of pristine fiber at 25lbf/min


99

11

12

13

14

15

16

0 20 40 60 80

AI (%R.H.)2

AI (%R.H.)4

Humidity (%R.H.)

Str

en

gth

(lb

f)

Dynamic tensile strength of pristine fiber at 0.5lbf/min


100

0

500

1000

1500

2000

0 20 40 60 80 100

%R.H.

No

rma

lize

d L

ife (

s)

AI (%R.H.)2

AI (%R.H.)4

Normalized life of pristine fiber in static bending


101

Optical Fiber Damage & Failure

Life is extremely sensitive to initial defect size:

tf a10

We are commonly concerned with sub-micron defects, and a 25% increase in size is significant!

102

0

0.2

0.4

0.6

0.8

1

1.8 1.9 2 2.1 2.2 2.3

Pro

babi

lity

Initial Defect Size (nm)

Initial Defects in ‘Pristine’ Fiber

103

Optical Fiber Testing

We can predict life under given loading if we know initial defect size and (in case of bending) location.

Static tests are by far the most sensitive to defect size, but they are often not very practical.

For most (all?) practical purposes defect sizes can be conveniently assessed through dynamic strength.

Dynamic bending measurements are very common, but should be carefully interpreted in terms of statistics of defects.

104

)2ba(oEE 1

Optical Fiber Bending

Account for non-linearstress-strain relationship:

‘Effective gage length’ is much less than in tensile test, especially if considered in terms of maximum tensile stress:

Slope of single mode Weibull distribution is the same, but mean is higher !

105

1.E-02

1.E+00

1.E+02

1.E+04

1.E+06

2 3 4 5 6

GPaMaximum Tensile Stress (GPa)

106

104

102

100

10-2

Lif

e (

s)

Bending

Tension

‘Pristine’ Fibers in Static Tension & Bending

106

Optical Fiber Damage

For all practical purposes it is impossible to

damage fiber significantly without penetrating coating

penetrate coating without damaging fiber significantly

Fiber is damaged by cleaving, stripping, wiping, splicing, ...

107

0

0.2

0.4

0.6

0.8

1

0 100 200 300 400

Pro

babi

lity


Initial Defects in Stripped Fiber

108

Initial Defects

0

0.2

0.4

0.6

0.8

1

0 100 200 300 400

Pro

babi

lity


spliced, Program 1

spliced, Program 6 stripped only

109

Optical Fiber Damage

Damage distribution is sensitive to stripping parameters (stripper, strip length, wiping, ...), but the largest defects may not be.

Damage distribution is often non-uniform, making 2-point bending tests more difficult/risky to interpret.

Cleaving and/or splicing caused additional (more consistent) damage, but largest defects were similar.

Damage distribution (strength of splice) was sensitive to combination of splicing recipe and fiber(s): SMF, EDF

110

‘Specs’ Taking reasonable levels of statistics into account we suggest (very conservatively, aside from optical considerations) limiting:

Handling (Immediate Failure) Radius of curvature >70mil for pristine fibers

>3.6” for splices (>>1”)

‘Permanent’ (35 years), non-hermetic Tension <1.2lbf, radius > 0.5” for pristine fibers Tension <26g (!), radius > 10” for splices

Until further notice we suggest same ‘specs’ for cleaved+stripped fiber ends as for splices.

Crack growth data are needed for very low humidity levels in hermetic packages.

111

So When Do We Care?

As we gather more statistics crack growth formalism allows us to more quantitatively assess ‘what is important’:

The weakest out of one set of 10 stripped fibers tested would last 11 days at 50%R.H. bent to radius of 1” (remember optical isolator?).

Different splicing recipes gave mean life of 15 vs. 30 years under 0.6lbf of tension, but the former also had lower Weibull slope.

Extrapolations to first fail of 10,000 under 60g of tension (3.8” bend) gave 25 minutes vs. 35 years. While undoubtedly unrealistic this illustrates concern.

112

Summary Problem solving for, and product development with, manufacturers help define generic research topics.

AuSn soldering:Metallurgy, design of multilayersExperience with preforms

Adhesives:Automated depositionCure kineticsEffects of realistic configurations

Fibers:Damage/defectsQuantitative assessment of consequencesCleaving, stripping, wiping, splicing, fiber type, ...

Optoelectronics Packaging Research 2001

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