mike bixenman, d.b.a chief technology officer kyzen corporation sources... · 2020. 3. 3. · 2...

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Mike Bixenman, D.B.A. Chief Technology Officer Kyzen Corporation 430 Harding Industrial Drive Nashville, TN 37211 615-983-4530 Direct 615-584-9089 Cell mikeb@kyzen,.com

August 22, 2011 Gene Pettingill State of Delaware Department of Natural Resources and Environmental Control [email protected] RE: Comments, Stakeholder Review Draft 082710B GMP, OTC Model Rule for Solvent Degreasing 2011 Dear Mr. Pettingill, Kyzen Corporation is a supplier of precision cleaning agents to Electronic Hardware OEMs

(Original Equipment Manufacturers), EMS (Electronic Manufacturing Services), and

Advanced Packaging (Microprocessors, Integrated Circuits, and Memory Devices)

companies as well as a broad array of Industrial Equipment Manufacturers (motor parts,

housings, etc.). Kyzen recently learned of the OTC Model Rule and ask that your department

consider this late response.

Table of Contents

1. Executive Summary

2. Electronic Assemblies

3. Solubility Methodologies

4. Contamination and its Effects on Electronic Assemblies

5. Five Cleaning Forces

6. Comments to the OTC Model Rule

7. Aqueous Cleaning Processes

8. Exhaust Engineering Controls

9. Conclusions

10. References

11. Mike Bixenman Qualifications

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1.0 Executive Summary

Cleaning is an important step in assuring reliability of the electronics device for its intended

function. The OTC Model Rule for Solvent Degreasing 2011 section on cold cleaners with a

recommended limit of permissible VOC to 25 grams/liter is a concern. As devices

miniaturize in size, the flux composition in the solder alloy relies on higher molecular weight

resins, activators, and functional additives to facilitate a strong metallurgical bond. The

cleaning agents needed to remove flux residues from circuit assemblies require a

combination of dispersive, polar, and hydrogen bonding forces. A VOC limit of 25

grams/liter is inoperable for a vast majority of the solder material residues used when

assembling complex circuitry.

Over the past 10 years, there have been significant advances in aqueous cleaning agents and

cleaning equipment for cleaning electronic assemblies. Formulations with less than 25 grams

/ liter VOC have been designed, but data from numerous studies indicate that these cleaning

products do not match up well with many of the common flux types used to assemble printed

circuit boards. Kyzen has worked with numerous electronic assembly companies in the State

of California subject to the 25 grams/liter VOC rule. For high value production, many of

these companies have located their assembly operations outside California, with this rule

being one of those considerations for leaving California.

Electronic manufacturers are faced with the dilemma of determining the level of cleanliness

needed to produce reliable hardware. The question of “how clean is clean” is more

challenging as conductors and circuit traces are increasingly narrower.9 Residues on a printed

board, component, or printed board assembly increase the risk of premature failure or

improper function, complicate the manufacturing process, and represent a decrease in quality.

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Kyzen has compiled a library of solubility data on many of the soils used to build electronic

assemblies. The flux component is an important enabler to creating acceptable solder

connections. The soldering materials required to assemble complex circuitry must be stable

at temperatures exceeding 240°C. At these elevated temperatures, flux compositions must be

thermally stable. Water soluble flux compositions do not possess the thermal stability

required to solder many lead-free circuit assemblies. Cleaning products formulated at 25

grams / liter do not remove many of these soils. Low volatile oxygenated solvents formulated

into aqueous engineered materials have been successfully combined with water for cleaning

most of the residue types present when assembling printed circuit boards.

To achieve the desired effect, the cleaning formulation requires a combination of dispersive

(solvency), polarity, and hydrogen bonding forces. Supplementing the solvency with

inorganic builders, bases, and / or acids creates significant material compatibility, reliability

and subpar cleaning concerns. For building electronic hardware, cleaning agents that allow

the use of VOC materials up to 200 grams / liter provides formulation flexibility for meeting

electronic assembly cleaning needs.

2.0 Electronic Assemblies

Electronic devices innovations have changed the way people communicate, interact and

work. As the current trends toward miniaturization take hold, proper cleanliness levels

become more difficult to achieve. High density circuit designs by definition allow only

smaller spacing between conductors yielding a larger electric field, which in conjunction

with insufficient cleaning can lead to electrochemical failures.

Cleaning is an important step in assuring reliability of the electronics device for its intended

function. As devices miniaturize in size, the flux composition in the solder alloy relies on

higher molecular weight resins, activators, and functional additives to facilitate a strong

metallurgical bond. The cleaning agents needed to remove flux residues from circuit

assemblies require a combination of dispersive, polar, and hydrogen bonding forces. This

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response to the OTC seeks to help the commission understand the need for cleaning and

limits needed to accomplish the cleaning task.

3.0 Solubility Methodologies

The process cleaning rate theorem holds that the rate at which a solvent or cleaning agent

dissolves a residue (static rate) plus mechanical energy (dynamic rate) equals the process

cleaning rate.1 To determine the static cleaning rate (rate at which the cleaning agent

dissolves the residue in the absence of mechanical energy), Kyzen uses two static cleaning

tests. The first test develops a composite solubility parameter for each flux residue in the test

matrix. The solubility parameter provides insight into the material sets that dissolve the

residue and the chemical characteristics of the residue. The second test exposes each flux

residue to different cleaning agents in an effort to match up the right cleaning agent to the

soil matrix. This testing provides insight into the technology base options for cleaning the

residue set.

The test methodology defines a sphere (Figure 1) from the properties of specific solvents and

engineered cleaning agents that were exposed to the soil. The test provides a set of

solvent/cleaning agent properties that match up (dissolve) the soils in the test matrix. The

objective is to develop a sphere whose circumference is defined by the solvents/cleaning

agents that dissolve the soil (inside solvents represented by blue circles). Solvents/cleaning

agent’s inside the sphere are considered relevant solvents, which have properties that require

the least amount of mechanical work to dissolve the soil.

Red squares represent solvents/cleaning agents that did not dissolve the soil efficiently.

These solvents/cleaning agents are considered outside solvents. The properties of the inside

and outside solvents/cleaning agents provide insight into the properties of the soil and forces

needed within a designed cleaning agent for dissolving the soil.

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Figure 1: Solubility Sphere

Each solvent tested has a dispersive, polarity, and hydrogen bonding value (Figure 2). These

values can be used to determine the optimal properties from which a cleaning agent will

rapidly dissolve the soil. The values for each solvent and their distance from the center of the

sphere can be used to calculate a composite solubility parameter for the soil.

Inside Solvents

Outside Solvents

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Figure 2: Solvent Families Tested2

Oxygenated solvents in combination with functional additives have been formulated with

water and are highly effective at removing rosin, no-clean, and water soluble flux residues.

The cleaning agents are effective at concentration ranges of 3-20% in water, depending on

the flux residue composition. At these concentration levels, the VOC content ranges from 20-

180 grams per liter. Figure 3 shows a second Teas chart showing the solvents position.

Higher dispersive forces are in the right hand corner, higher polarity forces increase in height

on the right side of the triangle, and higher hydrogen bonding forces are closer to the base on

the left side of the triangle. For effective cleaning, these forces need to align with these same

forces in the residue. For example, a no-clean flux residue (most common in industry)

contains a combination of materials encased in a resin. To clean this residue, the cleaning

agent requires a combination of dispersive forces to dissolve the resin, polarity forces to

dissolve polar materials through positive and negative attractions, and hydrogen bonding

forces to solubilize the residue in an aqueous medium. By taking away any one of these

forces, the cleaning medium will not be optimal.

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Figure 3: Solvent Positions within the Solubility Sphere3

Other factors such as temperature, concentration of aqueous cleaning agents, and time can be

designed into the test matrix. These other factors provide information for determining the

process window. The test methodology provides two critical insights:

1.) The chemical properties needed to dissolve the soil

2.) The process conditions in the form of time, temperature, and concentration

needed to clean the soil in the selected cleaning equipment.

A limitation of static testing methodologies is that the method does not take into account

dynamic energy and its effects on cleaning the part. Dynamic energy delivers the cleaning

agent to the soil and with the right forces improves cleaning performance, even with

boundary cleaning agents. Stronger forces applied directly to the source have been found to

improve soil removal. In theory, cleaning agents that are a closer match to the soil

complement the source of energy and open the process window.

Higher Dispersive Forces

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Solubility testing methodology can be used to develop and correlate the solubility properties

of known specific solvent / cleaning agent families to determine the cleaning properties for

any soil. This method was used to determine the cleaning properties needed to clean flux

residues from the following soldering materials.

1. Lead-Free Water Soluble #1

2. Lead-Free Water Soluble #2

3. Tin-Lead No-Clean #1

4. Tin-Lead No-Clean #2

5. Lead-Free No-Clean #1

6. Lead-Free No=Clean #2

The six solder pastes in this study were reflowed onto test vehicles and exposed to a series of

solvents with known solubility parameters. The test coupons were graded based on each

solvent’s ability to dissolve the residue. The test values were used to calculate a composite

solubility parameter for each solder paste tested.

Each test solvent has a dispersive value (solvency power for dissolving a soil), polarity value

(positive or negative charge attractions), and hydrogen bonding value (sharing electrons with

electro-negative atoms such as oxygen, nitrogen, and fluorine). Each of the solder paste flux

residues in the test matrix were immersed into the test solvents. The test coupons were

graded using values between one and six based on the solvent / cleaning agent’s affinity to

dissolve the soil. A “1” represents an inside solvent/cleaning agent that matches up well with

the soil and a score of “6” has no effect (Figure 4/Table 1).

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Figure 4: Grading Scale 1-6

Score Description 1 Easily cleaned – No residue 2 Light residue 3 Moderate residue - Boundary cleaning agent 4 Reluctant to clean 5 Low level cleaning 6 No interaction with cleaning agent

Table 1: Grading Description

The combined dispersive, polarity, and hydrogen bonding values for each soil tested were

used to calculate a composite set of solubility values for each soil (Figure 5). These values

provide insight into the chemical properties needed to dissolve the soil matrix. Soils with

high dispersive values tend to be more covalent in structure. Soils with high polarity values

possess reactive sites with solvents that have a partial positive or negative charge in the

valence electron shell, which increases dissolution from the forces of attraction. Soils with

high hydrogen bonding values tend to have oxygen or nitrogen within the molecular structure

that readily share their electrons with hydrogen, which improves the soils dissolution in water

based cleaning agents.

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0

5

10

15

20

25

Dispersive Value

Polarity Value

Hydrogen Bonding Value

Figure 5: Solubility Values

Water Soluble Lead Free Solder Paste Flux Residues

The solubility parameter for water soluble lead-free solder paste #1 had a moderate

dispersive value, low polarity value and high hydrogen bonding value. The solubility

parameter for water soluble lead-free solder paste #2 had a moderate dispersive, polarity and

hydrogen bonding values. Figure 6 provides a view of the solvent families that were effective

at dissolving the flux residues from these two water soluble lead-free solder pastes.

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Solvent Family

Mea

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Water Soluble LF 1Water Soluble LF 2

Soil

Interaction Plot for Water Soluble Lead-Free Solder Pastes Data Means

Figure 6: Solvent Family Interaction on Water Soluble Soils

Water soluble flux residue #2 was easily dissolved in many of the solvent families while

Water soluble flux residue #1 was less dispersive in a number of the solvent families. The

data indicates that water soluble paste #1 will be more challenging to clean.

Tin-Lead No-Clean Solder Paste Flux Residues

The solubility parameter for tin-lead no clean solder paste #1 had a high dispersive value,

low polarity value and moderate hydrogen bonding value. The solubility parameter for tin-

lead no clean solder paste #2 had a moderate dispersive, low polarity and low hydrogen

bonding values. Figure 7 provides a view of the solvent families that were effective at

dissolving the flux residues from these two tin-lead no clean solder pastes.

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Mea

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Tin-Lead No Clean 1Tin-Lead No Clean 2

Soil

Interaction Plot for Tin-Lead No-Clean Solder PastesData Means

Figure 7: Solvent Family Interaction on Tin-Lead NC Soils

The solubility properties of the two tin-lead no-clean soils were similar. The data indicates

that the cleaning performance for these two soils will be similar.

Lead-Free No-Clean Solder Paste Flux Residues

The solubility parameter for lead-free no clean solder paste #1 had a high dispersive value,

low polarity value and moderate hydrogen bonding value. The solubility parameter for lead-

free no clean solder paste #2 had a high dispersive, moderate polarity and moderate hydrogen

bonding values. Figure 8 provides a view of the solvent families that were effective at

dissolving the flux residues from these two lead-free no clean solder pastes.

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Mea

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Lead-Free No Clean 2Lead Free No Clean 1

Soil

Interaction Plot for Lead Free No-Clean Solder Pastes Data Means

Figure 8: Solvent Family Interaction on Lead-Free NC Soils

The solubility properties for the two lead-free no clean solder pastes were also very similar.

A stark contrast to the tin-lead and water soluble no clean solder pastes is that the lead-free

no clean solder pastes were much harder to clean.

Solubility testing gives the formulator insight into the make-up of the soil and the forces

needed to clean the soil. This data provides insight into the dispersive, polarity, and hydrogen

bonding forces needed within the cleaning agent to remove the soil. Other techniques such as

FTIR, GCMS, and HPLC can be used to characterize the organic makeup of the soil (Figure

9).

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Figure 9: Utilize FTIR, GC-MS, and HPLV, to Characterize Soil Differences10

Matching the Cleaning Agent to the Soil

The first set of test values found the interaction of different solvent families on the solder

paste flux residues in the test matrix. This test provides an overview of aqueous cleaning

solvents that rapidly dissolve the soil. Process conditions in the form of VOC content, time,

temperature and concentration were tested to determine the optimal condition for removing

the soil. The operating premise is that “cleaning agents with like properties to the soil will

matchup and dissolve the soil.” The data findings compare and contrast the static cleaning

rate for four aqueous cleaning agents with different levels of VOC.

The static cleaning rate was developed on four aqueous cleaning agents. Table 2 lists the

cleaning agent properties. The aqueous products are formulated as concentrated engineered

compositions designed to be diluted with water. Three concentration levels were tested with

three solution temperatures ran at each concentration. The test vehicles were graded using the

scale in Figure 3 and Table 1.

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Cleaning Agent Conc. Levels

Tested

Temp.

Levels

Tested

VOC

grams/liter

pH

High Solvency/ Low Reactivity

(HSLR)

1.) 10%

2.) 15%

3.) 20%

1.) 20°C

2.) 40°C

3.) 60°C

1.) 94

2.) 141

3.) 188

9.8

Medium Solvency/Medium

Reactivity (MSMR)

4.) 10%

5.) 15%

6.) 20%

4.) 20°C

5.) 40°C

6.) 60°C

4.) 60.9

5.) 91.35

6.) 121.8

10.6

Medium Solvency/High

Reactivity (MSHR)

7.) 10%

8.) 15%

9.) 20%

7.) 20°C

8.) 40°C

9.) 60°C

7.) 88.9

8.) 133.35

9.) 177.8

11.5

Low Solvency/ High Reactivity

(LSHR)

10.) 10%

11.) 15%

12.) 20%

10.) 20°C

11.) 40°C

12.) 60°C

10.) 19.5

11.) 29.25

12). 39

11.0

Table 2: Aqueous Cleaning Factors / Levels Tested

The main effects plot for the two water soluble lead free solder pastes (Figure 10) provides

meaningful process information. Pay attention to the grading scale as described in Table 1.

All four cleaning agents are effective at cleaning the water soluble soils including the Low

Solvency / High Reactivity cleaning agent that would meet the proposed limit of 25 grams

per liter. This is not unexpected since these residues are designed to be cleaned with water

only. The question one may ask is why not use water soluble solder pastes on all assembly

types. The answer is that water soluble flux residues are highly active, and if left trapped

under tight components, dendritic electrochemical migration grows rapidly. The second

concern is that water soluble fluxes cannot withstand the added heat need when soldering

lead-free alloys on highly dense components circuit designs. Assemblers building high

reliability hardware cannot risk highly active fluxes when failure cannot be tolerated.

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MSMR

MSHR

LSHR

HSLR

6

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Cleaning Agent

Mea

n

Conc.

Temp VOC

Main Effects Plot for Water Soluble Flux Data Means

Figure 10: Main Effects Plot for Lead-Free Water Soluble Fluxes

The main effects plot for the tin-lead no clean solder pastes (Figure 11) also provides


The High Solvency / Low Reactivity and Medium Solvency / High Reactivity provided the

best static cleaning rate for the two soils evaluated. Cleaning performance improved as the

cleaning agent concentration and temperature increased. The data indicates that VOC content

in the range of 130 -170 grams per liter provided the best static cleaning rate.

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MSMR

MSHR

LSHR

HSLR

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Cleaning Agent

Mea

n

Conc.

Temp VOC

Main Effects Plot for Lead-Free Tin-Lead Flux Data Means

Figure 11: Main Effects Plot for Tin-Lead No-Clean Flux

The main effects plot for the lead-free no clean solder pastes (Figure 12) also provides


The High Solvency / Low Reactivity cleaning agent provided the best static cleaning rate for

the two soils evaluated. Cleaning performance improved as the cleaning agent concentration

and temperature increased. The data indicates that VOC content in the range of 140 -188

grams per liter provided the best static cleaning rate.

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MSMR

MSHR

LSHR

HSLR

4.5

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Mea

n

Conc.

Temp VOC

Main Effects Plot for Lead-Free No-CleanData Means

Figure 12: Main Effect Plot for Lead-Free No-Clean Flux

Solubility testing provides an accurate indicator of soil properties and the forces needed to

clean those soils. Documenting these methodologies may be helpful to the commission in

your assessment of what is needed for cleaning high valued circuit assemblies.

4.0 Contamination and its Effects on Electronic Assemblies

Increased electrical device functionality results from closer spacing between electrical solder

connections (cathode and anode) and more functions in a smaller area. Device

miniaturization increases the electric field attraction between conductors. Process and service

related contaminants accelerate the potential for device failures. Corrosion problems decrease

product and reduce functionality.

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Ionic and non-ionic residues can occur from incoming components, soldering, and handling.

Ion migration leads to current leakage, galvanic coupling, and formation of electrochemical

cells.6 Cleaning is commonly considered based on the end use environment – Military,

Defense, Aerospace, Medical, Automotive, Information Technology, and Industrial etc. The

design / service life of the product (i.e. 90 days, 3 years, 20 years, 50 year, Life-time) must be

considered. The consequence of failure is also a factor (example: cell phone vs. pace maker)

when determining the value of cleaning.

No-clean soldering materials were introduced as a replacement for ozone depleting cleaning

agents in the early 1990’s. The hope was that cleaning could be eliminated as a part of the

assembly process. No-clean soldering technology is driven by cost pressures and difficulty of

cleaning highly dense printed circuit assemblies. True no-clean processes require stringent

controls of all incoming components and their level of cleanliness. All phases of the

assembly process must be controlled to prevent ionic contamination.

Today, no clean assembly processes are a source of concern within industry especially when

coupled with reductions in lead pitch and conductor spacing. New reliability risks are

introduced with the move to lead-free technology, new board finishes, exposed copper and

silver, tin whiskers, and highly active flux compositions.

With higher functioning devices, electronic assemblers are faced with the dilemma of

determining the level of cleanliness needed to produce reliable hardware. The question of

how clean is clean enough is more challenging to answer as conductors and circuit traces are

increasingly narrower. An added problem is that most assemblers have no background in

chemistry, chemical interactions, or analytical test methods. Most do not know how to

measure or define cleanliness, nor can they recognize process problems related to residues.

Figure 1 provides a simplified view of the materials used to build electronic assemblies.

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Figure 1: Electronic Assembly Process

Advanced package functionality achieves higher processing using tighter spacing between

conductors, higher frequency clock speeds and stacked packages. Contamination from the

assembly and joining can facilitate the movement of electrons through adjacent metal

conductors.7 In the presence of moisture from the environment and voltage, metallic

filaments can migrate through contamination to cause intermittent device failures. In some

cases, the failures will recover and in other cases the device will short and fail.

Bump 6 Bump 5 Bump 4 Bump 3 Bump 2 Bump 1Bump 6 Bump 5 Bump 4 Bump 3 Bump 2 Bump 1

Figure 2: Electromigration in the Presence of Ionic Contamination and Moisture

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Ionic contaminants can facilitate the growth of metal filaments between conductors on the

circuit assemblies. The filaments grow from the cathode to the anode. In the presence of

atmospheric moisture, ionic contaminants can dissolve metal (cation with a positive charge at

the anode) at one of the conductors and be transported through magnetic attraction when

powering up the device with electrical voltage (Figure 3).

Figure 3: Electrochemical Migration

One of the cleaning challenges is that over the past 10 years, the size of electronics has

reduced by over 70%. Integrated circuits have reduced by over 90%. Constant voltage rises

inversely with conductor spacing. As the distances between two oppositely charged

conductor’s decreases, time-to-failure decreases. The reason is that contamination has a less

distance to migrate. The trends toward miniaturization increase the importance on cleaning.

5.0 Five Cleaning Forces

Five forces that directly influence electronic assembly cleaning properties are the solder flux,

heat exposure, component gap, cleaning agent, and cleaning equipment.9 Variations in any of

these factors can and does influence the cleaning rate.

Soldering Flux

Solder alloys rapidly oxidize upon exposure to air, moisture, and heat.10 Oxidation is caused

by exposure to oxygen in air, which results in a non-conductive and non-solderable metallic

surface. Solder flux is a chemical cleaner that removes oxidation form metal surfaces,

facilitates wetting, and improves metallurgical bonding. When flux is heated, low boiling

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constituents within the flux evaporate, flux activators remove surface oxidation, and oxygen

barriers (rosin/resins) protect the alloys from re-oxidation during the solder process. During

the soldering process, heating and cooling ramp rates must be compatible with the assembly

and components. The time of exposure to high temperatures must be defined and maintained.

Flux and cleaning agent advances of the past 20-years have kept pace with component and

board assembly technology advances. Rosin, low-solids, no-clean, and water soluble flux

technologies designed for eutectic tin-lead were readily cleanable even after multiple

soldering processes. The same cannot always be stated for lead-free soldering.

Miniaturization and lead-free soldering require more active and stable flux compositions that

remove oxidization with less flux, wet higher surface tension alloys, and protect the

underlying metal from oxidation during the soldering process. The cleaning properties of

lead-free flux compositions, including water soluble, have changed. The residues are harder

and require more active cleaning agents and mechanical to remove the flux residues.

Heat Exposure

The reflow process heats the circuit board plus components held by solder paste through

successively higher temperatures. The solder profile progressively starts by evaporating flux

volatiles, initiates flux activation, raises the components to be joined to a temperature which

is sufficiently consistent for the solder to flow evenly onto all surfaces, and reflows the solder

paste over board finishes to facilitate solder connections. Temperature excursions and the

time exposed to liquidus solder temperatures influence cleaning properties.

The soldering process can be affected by the mass of the associated component, proximity

and mass of neighboring components, the size of the pads, and the amount of heat that travels

through the tracks and boards.11 These factors increase demands on the flux, which has a

significant influence on quality and low defect soldering rates. This task becomes more

difficult with highly dense miniaturized designs and lead-free soldering. To address these

complexities, the flux must be stable to high temperatures; resist charring, oxidation and

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burning; and provide a resistant oxygen barrier.11 These properties change the solubility and

cleaning properties of flux residue post soldering.

Component Gap

Component miniaturization decreases the spacing between conductors.13 During solder

reflow, flux under fills the bottom side of the component (Figure 4). The distance from the

board surface to the bottom side of leadless components is consistently less than 2 mils. For

cleaning to occur, the cleaning agent must first wet the residue. To sufficiently wet the

residue, the cleaning process must break through the flux dam to create a flow channel.

Figure 5: QFN Component with Less 2 mils Gap

Cleaning under low gap components is increasingly more difficult due to the higher

molecular weight non-polar covalent resins being formulated into lead-free flux

compositions. With clearance gaps under components of less than 2 mils, and for small chip

caps, gaps less than 1 mil creates a highly difficult cleaning challenge.

Cleaning Agent

The critical differentiator for removing higher molecular weight flux residues is the cleaning

agent. The ideal cleaning agent is formulated with the greenest environmental properties

Flux Residue

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within performance limitations; rapidly dissolves polar protic, dipolar aprotic and non-polar

soils; and is easily rinsed leaving an ionic cleaned assembly. Since flux residues are a

composition of rosin, resins, activators, rheological additives and reacted ionic salt forms, the

cleaning agent requires a composition of materials that remove polar protic soils, dipolar

aprotic soils, and non-polar resins.

Aqueous cleaning agents can be engineered with materials that target ionic, polar covalent

and non-polar covalent materials found in the flux residue. Optimal cleaning agents requires

a range of materials that solvate non-polar solutes (organic phase) and water soluble solutes

with polar and hydrogen bonding forces to solubilize ionic residues (oxygenated and

inorganic phase). Using a combination of hydrophobic (oil loving) and hydrophilic (water

loving) materials, an aqueous material can be designed to remove electronic assembly soils.

Cleaning Equipment

With lower component heights, the cleaning equipment must deliver the cleaning agent to the

flux residue. Visible flux residues on leaded devices are typically not an issue to clean. The

issue is cleaning flux residues under component gaps on leadless components.

To remove flux residues under component gaps on leadless components, cleaning equipment

designs that deliver the cleaning agent to the source of the flux residue using spray in air are

commonly used. Typical spray-in-air cleaning machines are equipped with spray nozzles that

hit the board surface and then deflect to move the cleaning agent to the residue. Engineering

controls can be used to condense and recover both exhaust and effluent streams.

Summary of 5-Cleaning Forces

Variability in the five cleaning forces impacts cleaning consistency. Understanding the five

cleaning forces and how they apply to a particular cleaning process differentiates a process

that meets the cleaning objective versus one that fails to meet the process objective.

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Each of the 5-forces are multi-faceted and must be studied to understand their influence on

cleaning the flux residue from under leadless components and then integrated to achieve

process consistency. Failure to consider each of the 5-forces when designing the cleaning

process often leads to a poor cleaning process.

6.0 Comments to the OTC Model Rule for Solvent Degreasing 2011

a. Solvent Degreasing: The term Solvent Degreasing closely relates to a vapor

degreasing process composed of solvent related raw materials. In an effort to clarify

the rule intent, would it be more appropriate to rename to: OTC Model Rule for

Industrial Cleaning Processes 2011?

b. Exemptions under a State Version of the 2001 Model Rule: Electronic Assembly

including integrated circuits makes up one of the largest industries worldwide. The

complexity of these devices and within industries where failure must be avoided at all

cost, an exemption for this industry segment under the 2001 model rule is requested.

Affected industry segments should include Aerospace, Military, Defense, Medical

Automotive, Industrial, Information Technology, and Telecommunications.

c. Specifically, what does the 2001 rule mean? I did not locate the rule on the OTC

website.

d. How are “Low Volatility Solvents” considered under the 2011 Model Rule?

e. Section 3.0 a & b: A VOC content of 25 grams/liter for batch and inline cold

(aqueous) cleaners used for cleaning electronic assembly flux residues is inoperable.

A workable limit for removing electronic assembly flux residues using Low Volatility

Solvents in Water is roughly 150 grams/liter.

f. Section 3.0 c: One alternative is to allow the use of engineering controls on cold

cleaners that adsorb or condense VOCs to the design limit but allow the use of

aqueous cleaners with high levels of VOCs present up to the limit of 150 grams/liter.

g. Section 7.0: Please consider an exemption for the following industries who produce

electronic hardware: 1. Military/Defense, 2. Aerospace, 3. Medical, Automotive, 4.

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Telecommunications, 5.Networks and Information Technology, 6. Industrial

Controls, 7. Mobile Devices.

7.0 Aqueous Cleaning Processes

Over the past 10 years, there have been significant advances in aqueous cleaning agents and

cleaning equipment for cleaning electronic assemblies. Formulations with less than 25 grams

/ liter VOC do not match up well with the common flux types used to assemble printed

circuit boards.

Low volatile oxygenated solvents have been successfully combined with water for cleaning

the residue types present when assembling printed circuit boards. To achieve the desired

effect, the formulation requires a combination of dispersive (solvency), polarity, and

hydrogen bonding forces. Supplementing the solvency with inorganic builders, bases, and /

or acids creates significant material compatibility, reliability and subpar cleaning concerns.

Allowing up to 150 grams / liter of low volatility solvents provides formulation flexibility for

meeting electronic assembly cleaning needs.

8.0 Exhaust Engineering Controls

Technologies are available to condense water liquid – vapor from aqueous cleaning

processes. Inlet diverters can be used to drop out large water – vapor droplets. Gravity

separation of smaller droplets can be recovered using demisting technology.

One option is to allow a higher VOC limit as requested to 150 grams / liter when exhaust

engineering controls are implemented to reduce emitted VOCs at a pre-specified level.

9.0 Conclusion

Proper cleanliness levels on printed circuit boards have become more difficult to achieve.

Aqueous engineered cleaning agents designed with low volatility oxygenated solvents

combined with functional additives clean electronic assembly soils without damaging

27


component hardware. They cleaning agent is used in low dilutions in water. Effective levels

are workable in the range of 150 grams per liter.

We ask for the commission’s consideration in placing an exemption for electronic assembly

hardware cleaning that allow a VOC limit up to 150 grams per liter when engineered with

low volatility oxygenated solvents and used in cleaning equipment with engineered controls

for condensing emissions to a predetermined level.

10.0 References

1. Bixenman, M. & Zhang, P. (2011). Scientific Methodologies used to select the Best

Cleaning Agent. SMTA China South Shenzhen Conference.

2. Stach, S. & Bixenman, M. (2004, Sep). Optimizing Cleaning Energy in Batch and

Inline Spray Systems SMTAI Technical Conference. Donald Stephens Convention

Center, Rosemont, IL.

3. Burke, J. (2011). Solvents and Solubility. Handbook for Critical Cleaning, CRC

Press, Second Edition. Barbara and Ed Kanegsberg Editors.

4. Minizari, D., Jellesen, M.S., Moller, P., Wahlberg, P., & Ambat, R. (2009, Sep).

Electrochemical Migration on Electronic Chip Resistors in a Chloride Environment.

IEEE Transactions on Device and Materials Reliability. 9(3), 392-402.

5. Mackie, A. (2009). Electromigration: Our mutual Friend. SMTA Wafer Level

Packaging Conference. Santa Clara, CA.

6. IPC 5702. (2007, April). Guidelines for OEMs in Determining Acceptible Cleanliness

Levels on Unpopulated Boards. IPC, Bannockburn, IL.

7. Pippen, D.L. A Primer on Hand Soldering Electrical Connections. New Mexico State University.

8. Tarr, M. (n.d.) Wave Soldering. Creative Commons Attribution – Non Commercial – ShareAlike 2.0.

9. IPC (2011). IPC-CH-65B Guidelines for Cleaning of Printed Boards and Assemblies. IPC Association for Connecting Electronic Industries. Bannockburn, IL.

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10. Bixenman, M., Northrup, M., Buchan A., Russeau, J. & Jensen, T. (2011). Cleaning in an HDI World. IPC Midwest. Schaumberg, IL.

11.0 Mike Bixenman Qualifications

Mike is one of the joint founders and CTO of Kyzen Corporation. He is an active researcher

and innovator in the precision cleaning field. Mike chaired the IPC-CH-65B Guidelines for

Cleaning Printed Circuit Assemblies released in July 2011 and IPC-7526 Stencil Cleaning

Handbook. He has published over 100 research articles on the topic of precision cleaning.

Mike holds four earned degrees, including a Doctorate of Business Administration from the

University Of Phoenix School Of Advanced Studies.

Sincerely,

Mike Bixenman, D.B.A.

Chief Technology Officer

Kyzen Corporation

mike bixenman, d.b.a chief technology officer kyzen corporation sources... · 2020. 3. 3. · 2...

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