The Resilience of Adhesion Problems

Adhesion has become a necessary requirement of nearly all manufacturing processes across vastly diverse industries. Whether the application is parylene coating on circuit boards, adhesive-bonded fasteners on aircraft, lubricious coatings on medical tubing, FIPG sealing on flanges in vehicles, inkjet printing on polymer films or simply cleaning a material surface for downstream bonding; adhesion is the proverbial glue that holds all of these, and many many more, manufacturing operations together.

While the prevalence of adhesion technologies has increased significantly in manufacturing, the knowledge required to achieve predictable, consistent performance has not kept up. Nor have the methods of finding the things that cause inconsistencies, setbacks and failures of adhesion.

Some common adhesion issues include:

  • Pcb delamination
  • Automotive FIPG or RTV seals leaking
  • Paint chipping
  • Fisheyes or orange peels appearing in paint or coatings
  • Bonded parts not reliably holding
  • Medical tubing not being uniformly coated or appropriately lubricious
  • Structural glass panels not fully insulating a building
  • Ink coming off food and medicine labels
  • Plastic packaging coming unsealed
  • Automotive recalls due to steering column electronics malfunctioning
  • Moisture getting into lighting fixtures

fogged-headlight-caused-by-adhesion-issue

Adhesion problems can turn into chronic failures when they are addressed only at the application stage.

When these issues arise, the causes are rarely diagnosed.

Companies seeing these assembly and coating failures will typically direct all of their attention to the final application step. The logical fallacy to that appr oach is in assuming this step is the only place in the entire process that affects proper adhesion. In reality, reliable adhesion is determined by an interconnected system of cleaning operations, treatments, preparation steps, material handling, storage, testing and many other steps and procedures that can have a dramatic effect on adhesion outcomes. Adhesion problems can turn into chronic failures when they are addressed only at the application stage.

When an adhesion process is not defined in a holistic manner, encompassing every area and operation that could potentially affect the success of the application, then the definition is not expansive enough.

Download the eBook to get the Checklist

checklist-for-adhesion-failure-root-cause-analysisThe checklist provides a list of steps manufacturers can follow to get to the heart of adhesion failures occurring in their production process.

If these are followed, it will lead to identification, remediation and extermination of adhesion problems.

Download your copy of this complete eBook including the checklist by completing the form. 

Defining Your Adhesion Process

It’s common practice for manufacturers who experience set-backs in adhesion applications to see the problem as purely a mechanical issue. This can lead to the addition of steps and procedures as an attempt to fix the problem. When adhesion processes are defined only as the final steps of assemblage, or even widened out to also include cleaning and treatment operations, this leaves out many crucial areas, processes and operations that make an enormous difference in the quality of a surface before it is coated or bonded to.

A well-defined adhesion process identifies every Critical Control Point in the production process. A Critical Control Point is any place in which a material surface has the potential to be altered intentionally or unintentionally, with either a positive or negative effect on outcomes.

critical-control-points-define-adhesion-monitoring-points-in-manufacturing

This definition is purposefully vague because it needs to be inclusive of all areas that affect the state of a material surface, even ones that are not obviously a part of the production process.

Some examples of crucial, yet often overlooked points that affect adhesion are:

  • Changes made by suppliers to parts or components without alerting manufacturers
  • The state of the surface when parts and components are received from suppliers
  • factory-floor-storage-time-can-affect-adhesion-processThe surface during transport between facilities
  • The surface during storage
  • The state of the surface during handling at Receiving or while the parts and components are being moved throughout the facility
  • The types of packaging material that parts and components are stored in and how this might affect the surface
  • The environment in which the material or parts ar e stored near and how this might affect the surface
  • The amount of time the part or component has been exposed to th e production environment
  • The length of time the part or component is treated
  • The outtime after the part or component has been treated or washed
  • And many more

A thoroughly mapped out adhesion process, like the one shown in the diagram below , will include all of these points as places that need to be controlled. This will ensure that the material surface is not altered in a way that is detrimental to the overall adhesion success.

manufacturing-plan-diagram

Developing an appreciation for this fact includes an awareness that this is a very delicate and sometimes precarious process. The proper chemical make-up of a surface is imperative to adhesion success. Every adhesion process creates a surface with a particular chemical state; what manufacturers are not aware of is the chemical state they are creating on the material surface and what the chemical state should actually be in order to ensure proper adhesion. A lack of insight into the chemical characterization of the material surf ace means there is no nuanced understanding of what each surface preparation step is functionally contributing towards adhesion success.

Adhesion is fundamentally a chemical reaction that takes place at the top few molecular layers of a material surface between that surface and the adhesive or coating being applied to it.

It’s important to know exactly how every aspect of an adhesion process is getting the surface more fully prepared for flawless adhesion.

surface-cleaningCleaning - which can be defined as an operation where undesirable contamination is removed from the surface (sometimes large particulate, sometimes microscopic chemical debris) - is used to remove unwanted species from the surface to allow surface and adhesive to meet.

surface-activationSurface treatment - which can be defined as an operation where a surface is being bombarded by chemicals as a way to alter the chemistry of the surface (e.g. plasma treatment, corona, flame and any activation or passivation techniques) - is used to change surface into one that is ready to be adhered to.

Surface Abrasion or Ablation - which can be defined as strategic removal of a top surface layer of a material usually through mechanical (e.g. sanding, grit blasting, dry ice/CO2 blasting) or high energy (e.g. laser ablation) means - is used to strip away layers of a material to reveal the most adhesion-ready surface

All of this work can be undone (often times unknowingly) through the lack of understanding of all the factors that can affect the top few molecular layers of a material surface.

surface-too-dirty-for-adhesionTake a human fingerprint for instance. A single fingerprint leaves a layer of oils and fatty acids that is around 1000 molecular layers thick. The residue from a human’s breath is 100’s of molecules thick. What might seem to be insignificant changes in incoming material, storage and handling, processing or environment can actually result in enormous changes in the properties of a surface, and therefore the properties of an adhesive bond.

Creating and preserving a surface that is amenable to adhesion in order to meet prescribed performance standards requires precise management of the entire adhesion process.

Where do Adhesion Problems Come From?

Problems often originate at the earliest stages of production design and planning. Anticipation of future issues and establishment of specifications and checks to ensure control of these issues, are part of this development process. Without a full appreciation for all the places that adhesion issues and contamination can originate, mistakes can be made in material selection, treatment and cleaning equipment selection, order of preparation processes, and testing methods.

Flaws can unwittingly be built into the process by selecting materials that may have certain desirable attributes for the application but may, in fact, be chemically incompatible with an adhesive, coating, painting, primer or anything being put on the surface. Sometimes these incongruities can be overcome with the right treatment and cleaning processes, however, if the root cause is not assessed as being part and parcel to the materials themselves then the proper solution will never materialize.

This is just one of the many unexpected ways that the root cause of adhesion issues can go undiagnosed.

Root cause analysis narrows down the variables that could be leading to the adhesion problems so that efficient investigation, problem solving, and solution development can begin. Without this analysis, manufacturers can jump to conclusions that may seem to alleviate the symptoms but not actually cure the ailment. Manufacturers may spend a lot of money on additional cleaning or activation equipment because they may not know enough to understand the surface is possibly not prepared enough for adhesion. However, if the problem is due to a chemical contaminant their current or new equipment is not able to handle, then these additional steps may do absolutely nothing or could even make matters worse.

adhesion-on-glass

Without Root Cause Analysis, Solutions are Only Based on Guesses

At BTG Labs, we have worked with an architectural glass manufacturer who was experiencing trouble with their structural silicone bonded panels adhering properly. In order to solve the issue, they hired employees who would wipe every edge of the panels with isopropyl alcohol with the hope that this step would make a cleaner surface for the adhesive to stick to. The problems persisted as they often do. After analysis conducted by BTG Labs, it was determined that the chemical state of the surface, as it relates to adhesion, did not change after this IPA wiping step. The company implemented a new step in the process, dedicated resources to solving the issue, yet it did nothing for the success of the final adhesion step. Eventually the true cause of the issue was found to be due to widespread cleanliness issues throughout the adhesion process. The relationship with this manufacturer is on-going and they are implementing new cleaning techniques and surface quality monitoring.

If the true origins of the problem are not found and addressed directly then all of the attempts to correct the issues are based only on guesses and will only work as a small bandage if you’re lucky.

ultra-sonic-cleanerAnother common attempt to ameliorate adhesion problems is to add cleaning or activation equipment and steps. If a manufacturer believes a part or component is not getting clean enough once it goes through a wash process then it seems logical to put it back through the wash process for another cycle. This logic breaks down if the root cause of the problem originates with the parts washer itself.

If the fluids are not changed at the proper time then one unusually dirty part can cause the wash liquids to become contaminated and pass that on to subsequent parts. If the contamination levels of all the parts going into a wash system are not consistent, and therefore the level of contamination in the fluid is not fully controlled, then an additional run through the parts washer will have little to no real effect on eliminating the adhesion problem. Sometimes, the issue isn’t even with something that needs to be washed from the surface, but rather, chemically added to the surface. In any of these instances, taking a closer look at what impact the cleaning operation is having on the surface quality will reveal what steps need to be taken.

These steps may include changing the wash fluids, cleaning the w ash chamber, setting a specification for cleanliness coming into the wash process or utilizing a different preparation method.

With the popularity of plasma treatments to activate surfaces, manufacturers can rush to add this equipment to their production line not realizing that this might not be the answer to their root cause. If there is an invisible layer of oil on the surface they are trying to activate, then the plasma treatment will not even reach the intended surface. Instead, the plasma treatment will interact with the oil that remains in place on the surface, causing the adhesion performance loss all over again. The better approach would be to clean the surface prior to activation through plasma to ensure the intended surface is being treated.

To Get to the Root Cause, Think About Adhesion Holistically

Getting to the root cause by looking holistically at an adhesion process is the only way to act with precision, acuity and efficiency. There are three factors that can affect the efficacy of an adhesion process. Two of them are well-understand and highly controlled. The third is where root cause analysis can be deployed to get to the heart of adhesion failure.

  • The composition of the adhesive or coating (well-established and the strength of which is commonly understood and measured)
  • The bonding application and curing process (these processes have typically been perfected and tested in conjunction with the adhesive or coating manufacturer)
  • The quality of the bond surface (the level of quality is rarely measured or controlled leading to one of the key elements of adhesion being left up to chance)

Control of the first two is a part of any conventional quality management program. The third one typically falls into manufacturers’ blind spot because root cause analysis has not always included looking at the surface state for clues to where the provenance of problems are.

The Impact of Not Doing Proper Root Cause Analysis

The risk of not conducting proper root cause analysis is that adhesion problems will never be solved. The cost of incessant or unpredictable adhesion failures manifest in many ways:

Scrap - many companies countenance a certain amount of scrap as a cost of doing business. But when a 3% scrap rate (which has been able to be maintained by current operations) needs to be reduced to 2% due to economic pressures, then finding out exactly what is causing the scrap becomes paramount. If there is not an identifiable cause then there can’t be an identifiable solution.

Rework - much like the example of sending a part back through a parts washer, re-doing work that has already been done is a common symptom of adhesion issues. Excessive preparation steps that are ineffective can deeply cut into the bottom line.

Recalls - when adhesion failure is unpredictable due to unknown causes, then the failures may occur once the products are in the hands of the customers. With safety critical applications in medical devices, aerospace, consumer goods and other industries, recalls can be the result of failures which can have grave consequences.

Reputation costs - much like the previous cost, it can be extremely difficult for companies to combat bad press due to adhesion failures and unreliable products. With social media accelerating the dissemination of this kind of information, it’s all the more crucial for companies to stop adhesion problems before they start or get to the root cause quickly.

When surface quality (the third factor that affects adhesion, discussed earlier) is not understood to play an extremely important role in the totality of the manufacturing process then the value of adhesion isn’t appreciated.

dewetting-on-pcb

A comprehensive loss prevention program for manufacturing companies needs to include adhesion failure root cause analysis.

Own Your Adhesion Process

Companies are able to conduct their own root cause analysis, but they have to set up a systematic design of experiments (DOE) that is thoughtful and holistic. This study needs to encompass all of the Critical Control Points that were talked about earlier in this eBook. So those Critical Control Points must be identified prior to conducting the study so they know that every variable is being scrutinized.

critical-control-points-in-manufacturing

If a truly thorough study is done and the root cause of adhesion issues are found, manufacturers need to then optimize each step based on the results of the study. This might mean a full re-organization of cleaning steps or it could simply mean that something like the corona treatment parameters need to be tweaked for consistency. Without doing holistic analysis it’s impossible to know how systemic the issue is and how far upstream it begins.

Once the entire adhesion process has been optimized, implementation of verification steps will allow the tracking of any changes to the surface quality. Maintenance of the surface quality through monitoring is required to keep the adhesion process at this new standard. These verification steps need to be fast and easy to conduct, as well as being quantitative so the data can be accurate and actionable and not subjective.

The risks involved in companies going it alone to do this work include the large time investment cost of having current teams refocus on adhesion issue mitigation. Quality Assurance teams may not be prepared or have the capacity to take on this sort of study because it requires Materials Science expertise to deduce exactly where the root cause is without leaving out any Critical Control Points. Without the proper experience, expertise and equipment, this work is very difficult to execute properly. When done holistically and well, this analysis allows manufacturers the ability to maintain total, ongoing control of the adhesion process and build predictability into the outcomes.

When Materials Science expertise is utilized it gives manufacturers the ability to make informed decisions that allow them to build quality products that are free of problems related to cleanliness and poor adhesion.

Often manufacturers will look to their paint, coating and adhesive suppliers for assistance in doing this work. These suppliers have a ton of experience and expertise in a very narrow domain. They are very adept at giving insight into the application and curing or finishing of their product, but that leaves out the third element of adhesion--the quality of the bond surface. If the adhesive application and curing processes are controlled but adhesion failures remain, then the overall process needs to be considered.

surface-scientists-in-the-lab

Download the eBook to get the Checklist

checklist-for-adhesion-failure-root-cause-analysisThe checklist provides a list of steps manufacturers can follow to get to the heart of adhesion failures occurring in their production process.

If these are followed, it will lead to identification, remediation and extermination of adhesion problems.

Download your copy of this complete eBook including the checklist by completing the form. 

surface-scientists-analyzing-a-manufacturing-part

How Does BTGLabs Assist Companies Like Mine?

BTG Labs’ approach follows the best practices outlined above. We consider each manufacturer’s current plan and production process, work with them to optimize and control every critical aspect of that process and guide them to reliable adhesion and better products.

New call-to-actionBTG Labs maintains a state-of-the-art Materials Science laboratory, and its staff of materials science experts and chemists offers a broad array of materials science services to manufacturers, including many of the most advanced manufacturing companies in the world. Applying a novel approach to diagnostics, we receive customer samples, design specific tests, and issue comprehensive recommendations to the manufacturer to control their adhesion issues.

BTG Labs offers an advanced technological suite of surface measurement inspections products, hand-held and automated, to help manufacturers monitor and validate surface cleanliness conditions.

To get the whole scope of our approach to eliminating adhesion failure, download the BTG Labs’ Guide to Adhesion Science for Flawless Manufacturingebook.

If you would like immediate help to get to the root-cause of your adhesion issue, then please consider partnering with BTG Labs to conduct an Adhesion Process Survey which is one of our value-added services for our clients.