cleaning process do's and don’ts. - smta€¦ · evolution of technology – board and...

Presented by:Scott F. Cain

Original Slides by: Debbie Carboni

Kyzen Corp

Cleaning Process Do's and Don’ts.

Avoiding Common Pitfalls...

Evolution of technology – Board and Equipment

Board Design Considerations

Overcoming Environmental Challenges

Common machine set up blunders

Common Process Control blunders.

Common board fixturing blunders

Is your rinse effective enough?

How to effectively clean to meet the new standards, be reliable and prove it.

The Next 60+ Minutes

GOAL:

Answer your

questions

Modern Cleaning and Equipment

Evolution of Technology, Cleaning Methodology & Validation

Demand

High Frequency Devices

High Impedance Devices

High Voltage Devices

10 year+ life

Conformal Coated PCB

Products functioning in a Harsh

Environment

Component Challenges

Source: Dale Lee of Plexus Source: Bob Willis Consulting

These images are videos – double click to view

Customized tests

No Clean Paste Can Lead to Electrochemical Migration

I 295mA

24.4 mil

In-situ monitoring of

dendritic growth

Flu

x A

F

lux B

Custom-designed board

Bias 12V/mm

Cleaning or Considering Today

Modern Spray-in-Air Cleaning Tools

Factors that impact the rate function

Deflection energy (i.e., pressure at the board surface)

Nozzles type

Coverage

Modern Cleaning Agents

Both Inorganic and Organic in nature Solvent Phase

Targeted at non-polar soils

Aqueous Phase Targeted at polar soils

Functional additives Defoaming

Corrosion Inhibition

Lower surface tension

Bath life and loading

Rinsing

The Cleaning Process is Dynamic

BOARD DESIGN

CONSIDERATIONS

Eliminate ALL BTC’s

Solution #1 – Optimize PCB Design

Engineer For Cleanability

Make It Easy…ier

Access To Flux Residues Component to Component Spacing

Component Standoff Height

Solder Mask Clearance

Silk Screen Clearance

Solder Mask Type

Redirecting Flux Residue Location Between Pins & Thermal Pad (QFN)

Flux Cleanability

Access To Flux Residue

Board Layout

Increase Spacing Between

Components

Low Standoff Component

Large Package Size Components I.E. – High IO BGA’s/LGA’s

Tall Component Packages

Improved Access To Flux Residue

Increased Component Standoff Height

Solder Mask Design SMD, NSMD, No Solder Mask

Pad Design Thicker Copper – 1 oz > 2 oz > etc.

Smaller Lead To Pad Area Aspect Ratio –

Component Package Specific

Use Silk Screen to raise BTC corners

Remove Silk screen body outline to allow

for flow.

Dale Lee, Plexus

BTC Via Holes and Solder Mask

NSMD is better except for BGAs

Solder Mask Selection

Matte Finish Solder Mask Has Increase Surface Energy To Hold Flux To The Board (More Flux For Solder Joint Formation)

Dull/Low Reflection Appearance

More Difficult To Clean

Glossy Finish Solder Mask Has Low Surface Energy to hold Flux To The Board (Less Flux For Solder Joint Formation – Solder Balls, Icicles, Flags, etc.)

Highly Reflective Appearance

Easier To Clean

Not Preferred

Preferred

Dale Lee, Plexus

ENVIRONMENTAL

CONSIDERATIONS

Over coming Environmental Challenges

Global Harmonized System Internationally agreed upon standard

Hazard testing criteria

Universal warning pictograms

Safety data sheets with required information Hazard Classification

Physical Hazards

Flammability

Toxic substances

Health Hazards

Acute toxicity

Chronic toxicity

Environmental Hazards

Air

Water

Classification of mixtures

What does YOUR Local Publicly/Privately Owned Treatment Works considers Environmentally

friendly?

Biochemical oxygen demand (BOD) Limits vary even within same country/state

Chemical Oxygen Demand (COD) Limits vary even within same country/state

Total Solids – Mostly concerned with lead contamination

pH of waste water Generally treatment plants allow a pH range of 6-10

pH neutral does not mean wash solution is Safe to send to drain or to a waste water

treatment

Waste Water Management

Smell (while subjective) has an impact consciously and subconsciously.

Should not be strong

Should NOT Cause Physical reactions: Eye Irritations, skin irritation, Headache, Nausea

Machine Maintenance

Cause excessive scrubbing/rinsing in the wash or rinse tanks to keep the process in the process

limits

Ease of Concentration Monitoring

Real Time concentration Monitoring available

Eliminates operator from having to take taking manual concentration readings

Human Contact/Operator Experience

What’s in the Wash Bath?

Kapton Tape

Solder Balls

Solder Mask Materials

Paste/Flux

Unplanned contamination: Glue, underfill, Thread lock material, RTV,

Epoxy, grease….3rd SHIFT

Its not just Water and SOAP!

pH Balance

Typical Flux: 2 4 Modern Cleaning agents 7.5 10.5

COD/BOD Balance

Typically the lower the pH, the higher the COD

MACHINE SET UP BLUNDERS

Common

3. Water Supply

2. Nozzle Adjustments

1. Exhaust

Top 3 Set up Mistakes

Should be DI water for entire machine ALL the time. Good quality- Minimum 2 megohm (or your Set point)

low level set point.

Plumbing material: Material

DI water eats copper

Inlines: Enough to provide good flow in final rinse when other

parts of the machine are calling for water. Wash or rinse tank is filling (total of 38-40 liters/10-

12gallon per minute demand)

Water Supply

Nozzle Alignment

Fluid delivery should be across the entire assembly(s)

Spray bar alignment can impact the cleanliness effectiveness

Perpendicular on most spray is recommended

Slightly turn the airknife toward wash section

Deflector Plates on top of wash

Curtains between wash and chemical isolation sections

Inline Spray/Air Alignment

Other Blunders

Original ducting

should sit inside

Demister collar

at top side.

Demister collar

should sit inside

ducting/collar

from cleaning

machine.

Blunders Results

Best Installation Practices

PROCESS CONTROL

BLUNDERS

Common

Semi Automatic/Manual Monitoring

Data logging

Automate as much as possible

Use your machine alarm settings

with a window that meets your

cleanliness needs.

Don’t Ignore Alarms

Don’t forget Rinse and Dry

Process Control

Keep nozzles clean

Keep wash tanks clean

Keep Rinse water clean

PM – Daily/Weekly

PM’s and Alarms are the Key to Repeatability

BOARD FIXTURING AND

POSITIONING BLUNDERS

Common

Inline Top Spray Bars. Vs Bottom

More impingement energy from the top sprays

Place more difficult to clean facing towards the highest energy

Some machines do not have complete spray over entire converyor. The conveyor belt rail can cause a 1” Dead Zone on the bottom side sprays

When possible, clean between soldering processes

Understanding the batch Chamber Some Batch Machines

Not all boards may see the say pressure

Corners may have 2-3” Low pressure/flow

Batch Board Orientation

Avoid tall boards too close to short boards to avoid

Potential Shadowing When loading the basket

Boards should be spaced 1-3 inches apart

depending on potential shadowing and complexity

of assembly

Most complex assembly side down towards bottom

Face Connectors face down

Electrolytic Caps should be faced away from direct

heat source (heating element) if possible Or run

less than 130F

Ensures proper &

repeatable cleaning

Prevents foaming in the

rinse

Reduces costs

Reduces chemical drag-out

Reduces re-cleaning

Bad

Good

Proper spacing between pallets /PCB’s is key

Bad

Batch Fixturing

Inline Fixturing Designs

CONVEYOR BELT SECTIONS TO

PLACE ON TOP OF CONVEYOR

(NOT IN SAME DIRECTION)

A few more Bad Designs

Baskets Done Wrong • Decent open area

• ½” mesh belt is better

• Round wire mesh has

less drag-out.

Stamped metal, causes:

• Small opening shadows

components

• Diffuses impingement energy

(wash and rinse)

• Excessive drag-out

• Foaming in rinse

Top Hold good

Bottom Bad

Basket Board Spacing Improves cleaning by:

Spacing between assembly to prevent PCBs

on top of each other.

Open mesh or no mesh to allow for direct

energy each other

Bad

Pallet Considerations Raised closer to the sprays

increases energy Know what the height

limitation on the sprays

Total Height with pallet needs to be less than sprayable area

Open slots and holes for good drainage and less weight. Reduces excessive chemical

use

Prevents foaming in the rinse

Use the Whole Belt Keep 2-4” between pallets to prevent

excessive wash solution loss

PCB Placement to Improve Through Put

20" Conveyor 26" Conveyor

Assembly Length (in) 9.5"

Assembly Width (in) 3.5"

Spacing between assemblies 4

Multiple lane processing 2

capacity (boards/hour)

Throughput requirement (no. of boards/day) 5000

hours per day 23

boards needed per hour 217

boards needed per min 4

DON’T FORGET RINSING

Rinsing Issues Often observed under low standoff devices, tight spaces/crevices, and

connectors

Worsen with bath loading

Effectiveness on rinsing cannot be analyzed by ionic cleanliness

assessment methods

A common root cause of downstream process problems such as

conformal coating defects by poor adhesion and wetting

Possible intermittent shorts.

Final Cleanliness

Quick and Easy Surface Test

BAD

Poor wetting Poor adhesion

GOOD Clean Surface

Factors that Improve Rinsing Hot DI-water

Rinse zone is as important as the wash zone

Rinse time

Rinse pressure

Understanding the effects of FLUX Soil Loading

BAD

Poor wetting

Poor adhesion

GOOD Clean Surface

BE RELIABLE AND PROVE IT

How to effectively clean to meet the new standards,

On-Site Test Methods to Meet J-STD-001 Rev G.

Without Objective Evidence, Your “Number” does not mean Anything

Qualification vs. Production

Qualification

No flux loading

Visual, IC, Ionograph, and SIR

Rarely include rinse test.

No downstream process impact

assessment.

Single design test assemblies are

used. And may not have the same

components

Production

Heavy flux loading.

Visual/ Ionograph

Adhesion and wetting are critical to

downstream processes.

Wide variety of assembly geometries

(shadowing, entrapment, etc.)

Rework- unexpected work arounds

Cleaning Equipment and Parameters

Wash, Rinse, Dry

Handling

Process Control

Maintenance

Cleaning is A PROCESS

Cleaning Process Do’s and Don’ts

1. Set up your process Correct from the start

2. Understand the cause and effect each setting

3. Pay attention to board position and handling

4. Cleaning is not just the Wash Stage

5. New Process Control Tools are being introduced that can

provide process optimization and monitoring to meet

tomorrow’s challenges

Scott Cain Western Regional Manager Scott_Cain@kyzen.com Debbie Carboni Global Product Manager, Electronics Debbie_carboni@kyzen.com

Questions?