1 lead free wave's issue & troubleshooting 312007

8/2/2019 1 Lead Free Wave's Issue & Troubleshooting 312007

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PRIVILEGED AND CONFIDENTIAL MATERIALS

Lead Free Process:Issues & Trouble-shooting

Gilbert Renaud

Global Technical Manager


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Issues on Lead Frees?


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More Bridgings

Bad Hole Fillings

Cu DissolutionsCracks & Fillet Lifting

Blow Hole Effect


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Bridgings on Lead Frees?


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How to reduce it?

Pad design...

Carrier design...

Flux Choice...

Better Process Setting...


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What Pad Design for Lead Frees?


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Lead Free Board Design?

Lead Free Alloy: Surface Tension Higher than Sn/Pb

Worst draining skill. More bridging effect

Pads design in a different way.


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Solder Thieves to Pull the Alloy...

Sn/Pb:

Lead Frees:

Examples of Solder Thief

Designs

(Wave Direction) (Wave Direction)

Wave direction

(No short or much less)


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Other Choices...

Wave direction

Wave direction


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Some Field Design

No place for Thieves Ink separation


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Inks and Shapes


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Good Solder Thieves

(Wave Direction)


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Whats About for Carriers on Lead Frees?


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Some Field Examples.


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The Concern with this Processing of Sorts...

Some Pins too close the carriers

The Use of the Chip waves

Pallet Orientation vis a vis of the waves


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< 1 mm

Some Examples...

(Wave Direction)


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3mm

3 mm

Some pins < 1 mm of the mask

Some Examples...


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Shorts on difficult locations.

Even with 3.5 seconds of contacts

Some Examples...

More Place better Draining


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Orientations

Previous situation:

< 1mm

Wave directionMask wall

New status:

Wave direction

Shorts:

No Shorts:


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Wave direction

Board Rotation of 90

Close the masks

Orientations


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Good filling even on locations without pins

< 1mm

Orientations


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Carrier Thickness Rule(for an industrial processing).

Minimums between Pin and Mask:

Carrier Thickness /2


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An Example...

Connector pin

4 mm ( selective carrier)

About 1 mm

Connector pin

4 mm ( selective carrier)

2 mm thickness for a better draining ( chamfer)

Currents:

Improvements:

If not Contact times Longer More Copper Dissolution.


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1.5 mm

Pin Length...

Much less bridging effect and shorter contact


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The Chip wave Use?

Only for SMT Glued Components...

Only for Test Pads soldering.

If not bad Holes Filling + Shorts (Contact time longer for Fluxs)...


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Chip- Wave Gap too Big...

14 cm

Before Mains:176.5C

Chips No use.


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An Example...

Usuals:

1.4 second + 3.4 seconds = 4.8 seconds

Poor Holes filling


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Without Chips:

4.6 seconds.

Excellent Holes Filling

An Example...

N L d F W A li


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New Lead Free Wave Appliances

5-6cm

Tamura Device: HC- 33- 32 LF2

N L d F W A li


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New Lead Free Wave Appliances

8 cm

Soltecs

5 cm

JT: SM 450

Today: Chips Mains within 5 to 8 cm


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Cracks on SAC Alloys?


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More Cracks On SAC Alloys

SAC 305

SACX

Sn/Pb ( 63/37)


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SAC305

SACXTM 0307

Sn63Pb37

Th P ibl C ?


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For SAC 305:SAC305 cooling is in three stages.

The Ag3Sn platelets form first and produce a rigid matrix structure.

The other phases cool, the final volume reduction taking place in thelast portion to cool.

The rigid Ag3Sn matrix does not move leaving cracks as

the liquid shrinks away.

For SACX:The SACX cools in the same 3 stages, however there are much less

Ag3Sn platelets and the matrix is less rigid during cooling.

As the final shrinkage occurs the matrix is less rigid and

moves with the liquid alloy to form a smooth topography

The Possible Causes?


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Whats about the cooling rate?

To Reduce the cracks on surface.

To Mitigate the Fillet Lifting.


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Liquidus to Solidus: 3 steps.

Ag3Sn

Sn Dendrites

Eutectics


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The Microstructure of SACalloys (3-4% Ag) forms step

by step.

This results in the alloy

displaying a surface roughness

because of the shrinkage of the

eutectic liquid between the Sn

dendrites. The Ag3Sn particles

improve the reliability of thejoints.

Some Lead-Free alloys, such

as SACX0307 do not displayrough patches.

Courtesy of Celestica International Inc.

Snugovsky, Bagheri, Kelly, Romansky

SEM of rough patch on SAC387

solder sphere


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The Liquidus Volume Effect on Lead Frees

Cracks...

Volume reduction


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Wave Cracks on SAC alloys?

Cracks


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Cracks


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IPC-610-D ( 2005).

Specifies pass fail criteria for shrinkage cracks.

Crack must not touch the land or the leadBottom of the crack must be clearly visible

SAC305

Pass

Fail

Shrinkage Cracks high silver SAC Alloys


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The reliability not damaged

How to Reduce? Cooling faster on bottom side


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Coolings: about 8C/s

After Mains to 170C: 3-8C/s on the Joints.


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Whats About the Fillet Lifting?


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Fillet Lifting

Combination with Pb/Bi ( Bi > 4% and Pb > 0.2%)

Only on Double size Through Hole joints


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Fillet pivots away from the land as the joints coolsbetween the liquidus and solidus.

Effect can occur even where there is no melting range in the solder.

Large fraction of primary dendrites ( 60-80%) as led free joints solidify

Surface shrinkage cracking.


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How to Reduce or Solve it?

No lead ( > 0.2%) with Bismuth (>4%).

Strong Coolings on the Bottoms after the waves

( Cool Air Knife)


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Coolings: about 8- 10C/s

Request: after Mains to 200C: > 15C/s on the Joints.

A Customer Example...


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Cold Air Tube

8 cm


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(With the Cold Air Tube)

( Normals)

Anothers with SEHO...


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Close Wave Appliance...


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Cooling zone

MWS 2300: Cooling Module

NozzlesFan


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Wave Profile...

Cooling System on


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MWS 2300: Cooling Module

structure without cooling structure with cooling

Whats about on new wave devices?


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Cold Air System after wave on the Bottoms


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Cu Dissolution on Lead Frees?


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The Parameters Which Influence?

Board Finishing Contact Times

Pot Temperature. L.F Alloy Choice.

OSPs > Immersion Ag & Sn

> HaL > Ni - AusSingles: < 3.3 seconds

Plateds: < 4.6 seconds

SAC 305: 255C- 260C

SACX: 255C- 260CSACX: 2 times slower than SAC 305

Field Example S.


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Copper leaching on OSP Copper boards

Solder Bath temperature 260 Celcius : SAC305 alloy

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Initial

1000

2000

3500

4500

5500

6500

7500

8500

9500

12000

14000

16000

18000

20000

22000

24000

26000

28000

31000

Number of boards

PercentageMetals

Copper (Cu)

SAC300Added to

stabilise

SAC 305/ SA300 on OSP at 260CContact Time: 4.5 seconds

+ 0.01%/1000 Boards

Field ExampleI.


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% copper

0

0.1

0.2

0.3

0.40.5

0.6

19/12/20

04

18/01/20

05

17/02/20

05

19/03/20

05

18/04/20

05

18/05/20

05

SAC 305 at 260C

HAL Plating: SAC 305

Adding: SAC 300

Contacts: 0.6 s + 2.5 s = 3.1 seconds

Single Board.

Field ExampleL.


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Cu Evolution...

0.5

0.6

0.7

0.8

0.9

1

28/05/2005 17/07/2005 05/09/2005 25/10/2005 14/12/2005 02/02/2006 24/03/2006 13/05/2006

SACX at 260C

Singles: OSPs

Contacts: 0.9 s + 2.7 s = 3.6 seconds

Adding: (150 Kg of SACX0307 + 50 Kg of SACX0300)/ Week

Field ExampleJ.


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Cu Evolution...

0.5

0.6

0.7

0.8

0.9

1

08/04/2005 28/05/2005 17/07/2005 05/09/2005 25/10/2005 14/12/2005 02/02/2006 24/03/2006 13/05/2006

SACX at 255CSingles: OSPs

Contacts: 3.5 seconds.

SACX0300

SACX0307

Field ExampleA.


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Cu Evolution

0.5

0.6

0.7

0.8

0.9

1

23/01/2006 02/02/2006 12/02/2006 22/02/2006 04/03/2006 14/03/2006 24/03/2006

SACX at 260CSingles: OSP

Contacts: 3.5 seconds

SACX 0300

Adding now: SACX 0300

SACX0307


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So What Policy to Follow?


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The Bath Analysis will Determine it.

%Cu- % Pb Analysis on the Beginning gives the way to follow

For Bath Adding?

SAC 305 & SAC 300

SACX 0307 & SACX 0300


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SACX Versus SAC 305

SACX Dissolves 2 times Less than SAC 305


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Test Method: Copper foil 25m thick, cleaned, washed and fluxed.

Solder bath SACXTM (0.7%Cu, 1.01%Cu and 1.32%Cu) and SAC305

Bath temperature 270C

Immersion time 10sec Output, measure the change in composition of the solder bath.

Result:

SACX significantly less Cu dissolution than SAC305.

As copper increased in SACXTM

the dissolution rate reduced dramatically (saturationeffect).

At 1.01%Cu* the SACX had a copper dissolution rate 40% of the SAC305s

Alloy

Cu content

beforeimmersion

Cu content after

immersion

Dissolution rate

Micron/sec

SACX0307 0.7 0.79 0.17

SACX-1.01Cu 1.01 1.06 0.09

SACX-1.32Cu 1.32 1.33 0.02

SAC305 0.51 0.63 0.22

* 1.01%Cu hasbeen shown to

be acceptable for

SACXTM in service

Dissol tion rate Micron/sec

SACX Dissolves 2 times Less than SAC 305


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Alloy

Cu content

before

immersion

Cu content after

immersion

Dissolution rate

Micron/sec

SACX0307 0.7 0.79 0.17

SACX-1.01Cu 1.01 1.06 0.09

SACX-1.32Cu 1.32 1.33 0.02

SAC305 0.51 0.63 0.22

Dissolution rate Micron/sec

0

0.05

0.1

0.15

0.2

0.25

SACX0307 SACX-1.01Cu SACX-1.32Cu SAC305Alloy

Copperdissolutionrate


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Field Experiences with Low SACX

Copper dissolution on HALs

Low SACX 0307 versus SAC 305

Serigroup: 3 times less

Cemco: 2.2 times less


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The Blow Hole Phenomenon?


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Out- Gassing Effect.


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Why More Effect on Lead Frees?


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Pot Temperature higher

Contact Times Longer.

Lead Frees more Stringent

+ 30% to 50%

255C to 270C instead of 240- 245C


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Soldermask curing: not polymerised enough

Board material types

Hole drilling Quality

First copper flash ( KMnO4 + Chemical Cu)

Second electroplating: < 25

( Thin copper thicknesss)


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What Means Bad Drilling?

Bad Drilling


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Tear, Shear on board materialIrregular Shapes

Bad Drilling


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Metallisation Rupture


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Whats Bad First Metallisations?


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Permanganates

Solvent to soften the Epoxys

Good Permanganates to attack the epoxys

First Metallisations

Good Palladium deposit

Good Chemical Cu 0.5 ( 0.3- 0.8)

Cu Plating about 5

Flash


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Micro missing on first

chemicals

micro copper missing in the holes.

No metallization


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PRIVILEGED AND CONFIDENTIAL MATERIALSRupture in the metallisation


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What Means Good CU Plating?

Sn-Pbs: > 20 Lead Frees: > 25


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CU Plating too Thin...?

Bad barrier to the Out- Gassing Effect.

Good Plating Thickness.

Strengthen the first plating

Get more robust barrier to out- gassings

Cu Plating too thin


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Cu Plating too thinmicro rupture.


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Out- Gassing from Here

Good Plating Big Help.


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O R d ti L d F


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Our Recommendation on Lead Frees

Good Drilling

Cu Plating: 25

Wh t M G d D illi ?


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What Means Good Drilling?

S E l A i / E


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China.

Some Example Asia/ Europe(Board with 4 layers)

3000 hits before to change Drill

Drill Re- shape: 4- 5 times.

France

Drill Diameter: 0.7- 0.85 mm 1200 hits.

Drill Diameter: > 0.9 mm 1600 hits.

Re-Shape: Max 2 times.

S Fi ld Bl H l R lt


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Some Field Blow Holes Results.( With a Chinese PCB Supplier)

Usual Drilling Parameters + Thin CU plating: 40%

Usual Drillings + CU plating thicker: 14%

New Drills and CU plating > 25 : 0% of defect( In our Parameter requests)

B d H l Filli ?


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Bad Hole Filling?( On OSPs)

The Possible Causes ?


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Too Tough SMT Temperature Profile Damaging OSPs

Wave process Setting

OSP Plating Quality

Flux Choice.

What Means Tough SMTs ?


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What Means Tough SMT s?

Profile 2

Too High Peak not Good for OSPs


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Profile 3Profile 1

Profile 2

Profile 1: Quick and preserving the boards and Chemistry.

Profile 2: Warmer on preheat but quick enough preserves the Boards & Chemistry

Profile 3: Very long soak on preheat and long profile ( 130C to Liquidus: 3 mn)Stringent for board and Chemistry

Importance of a good OSPs ?


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Importance of a good OSP s?

Some Field Example


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Skips

Skips

Delay on Soldering..Worst hole filling.

Chip Wave usednot Normals

Entek Plus HT

Field Experience


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Entek Plus HT

Wider Process Window

Good Wave Process ?


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Good Wave Process?

Process Fundamentals ?

Spray Fluxer


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Preheat and Contact Times

Gap: Nozzle - Board

Flux Amount on the Board.

Air Blowing Pressure

Homogenous Deposit

Process Fundamentals?

Gap: Nozzle - Board


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Gap: Nozzle - Board

Gap : 13-14 cm

Board

Nozzle head

Normals : 6-8 cm

(50% Flux Lost)

(< 20% Lost)

Process Window ( OR) ?


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Process Window ( OR)?

Alcohol Bases

170-250 g Solids/cm

Water Bases

80- 150 g Solids/cm

Air Blowing Pressure?


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Air Blowing Pressure?

Too Strong: Flux touches the board and drops, less flux in the holes

Too Low: Unstable deposit and not enough flux on board.

Airs

Some examples...

Air pressure Flux amount inAlcohol Flux


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Air pressurein Bar

Flux amount ingram

0.8 2.571 2.34

1.6 1.99

2 1.442.4 1.2

Flux amount in gram

0

0.5

1

1.5

2

2.5

3

0 1 2 3

Flux amount in

gram

Usual setting: 1.8- 2.0 bar

Now:0.8 -1 bar 70% more flux

Alcohol Flux

Some examples...

VOC Free Flux


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Air blowingpressure in bar

Flux onboard in

gram0.2 2.570.3 2.860.5 2.430.7 2.08

Flux on board in gram

0

0.5

1

1.5

2

2.5

3

3.5

0 0.2 0.4 0.6 0.8

Flux on board in

gram

At 0.7 bar 37% of flux lost

Homogeneous Deposit


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Excellents Careful with Forced Convection

More Flux

The Preheats & Contact Time on L.F?


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(Board Thickness: 1.4 - 1.6 mm)


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Tin- Lead Optimums + 30%

Sn/Pb'sSingle's 1.8s 2.5s

Plated's 2.5 3.5

Lead free'sSingle's 2.3s 3.3 s

Plated's 3.3 s 4.6 s

( )

(Reduce the Copper Dissolutions)

Some Examples...

SACX at 255C

FR4 Board thickness: 1.6 mm


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a 6

Contact time: 7.2 seconds

Conveyor speed: 62 cm/mn

Conveyor speed: 100 cm/mn

Contact time: 4.2 seconds

FR4s: 1.4 mm

Some Examples...


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OSPs

SACX at 255C

Contact times: 1.5 s + 2.6 s = 4.1 s

SACX Bath Temperature:

255CSingle Board: 1.4 mm

Some Examples...


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Preheat: Top 105C -110C

Bottom 130C

Contact Times: 0.6 s + 2.5 s=3.1 seconds

EF 2202:Flux amount... 130 g RNV/cm

Preheats on OSPs

Preheats at 123C


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Preheats at 108C

40% less flux

Preheats < 115C better Hole Filling

Lead Free Flux Choices?


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Preheating higher : + 10-15C than Sn/Pb

Contact time: Longer than Sn/Pb

Lead Frees Worst wetting and Spreading than Sn/Pb


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Activation Higher and More robust Fluxetc

But need to pass the Reliability Tests:

(IPC J-STD 004 & Bellcore & JIS.)

Some Alpha Lead Free Fluxes?


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EF 6100 P


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OR L0 Solid Content: 3.6%

Alcohols No HalideNo Rosin

Comply:

SIR J-STD 004

Bellcore Tests ( SIR & E.M)

JIS

Aciditys: 24 mg KOH/g

EF 8000


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R0 L0 Solid Content:6.0%

Alcohols No HalideRosin

Comply:

SIR J-STD 004

Bellcore tests ( SIR & E.M.)

JIS SIR & E.M


EF 8000 EF 6100P


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Preheats: 111C

(Some Comparison)

EF 2202


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OR L0 Solid Content:3.5%

80% less Microballing than NR 310S and NR 330

VOC Free No HalideNo Rosin


Comply:SIR J-STD 004

Bellcore tests (SIR & E.M)

EF 2210


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OR L0

4.0% RNV; 31.5 mg KOH/g

Comply J-Std 004 & Bellcore tests ( SIR & E.M)

VOC FreeNo Halide No Rosin

Reduce Soldermask Surface TensionLess Micro-balling.

Long Contact Times ( 2- 7 seconds)

Improvement of EF 2202

I. EF 2210


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Fluxs: 210 g/cm.

Preheats: 112C on the BottomsContacts: 4.7 s

Items...

More Bridgings


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Covered

Bad Hole Fillings Cu Dissolutions

Cracks & Fillet Lifting Blow Hole Effect

Many Thanks for your Attention


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1 lead free wave's issue & troubleshooting 312007

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