Supply chain control is crucial to ensuring that the time, money and labor put into a production process doesn’t go to waste. Managing what comes into the production process has a massive impact on how effective and efficient the production process is ultimately going to be. For companies dealing with bonding, coating, printing, sealing, painting or cleaning, the adhesion process relies fully upon controlling the state of the material from the very beginning.
The idea of an adhesion process is, in reality, synonymous with the idea of a production process. Adhesion isn’t merely the final step in an assembly process to a end-product. Instead, adhesion is the culmination of holistically managed points throughout the entirety of the manufacturing process that affect the adhesion and performance of the final product. These Critical Control Points are points where the material surface has the opportunity to change, intentionally or unintentionally and are found in every part of the production process. The first Critical Control Point at the beginning (incoming parts) determines how effective all of the downstream operations will be. This Critical Control Point is the building block to the adhesion process.
Manufacturers are paying for consistent, clean parts and components from their suppliers and suppliers want to provide the product their customers need. Putting a measurable value on the quality of the material surfaces of all incoming parts satisfies both parties.
In manufacturing there are hard and fast specifications for all manner of criteria that both suppliers and manufacturers are eager to meet.
Quantitative specs are used for:
There is often not a quantifiable value on one key aspect of adhesion processes: surface cleanliness.
This measurement is extremely important to put in place. In manufacturing it can be said “As the surface goes, so goes the adhesion.” And it’s true. Since adhesion is a chemical reaction between the top few molecular layers of a surface and whatever is being applied to that surface, highly precise care needs to be taken to control what happens at that vanishingly small place. Even a human fingerprint is hundreds of molecular layers thick, so even the most minute contact with a surface can completely obliterate the surface treatment or cleaning that came before. Those microscopic elements can truly make or break your adhesion performance.
If possible, the surface quality specification should be put into use as soon as a new product is reaching its production phase. When Research and Development teams work on the details of how a new product can scale to production, instituting a baseline for incoming material cleanliness should be unquestionably a part of the conversation. This allows for each Critical Control Point (an abrasion step, plasma treatment, short or long term storage, actual assembly, etc.) down the line to be accepting consistent and verifiably ready materials.
BTG Labs worked with a large electronics manufacturer whose Supplier Quality Manager asked “How do I create a spec to manage my supply chain to make sure I get clean parts in the door?” It’s a great question, and once an adhesion problem has already arisen, remediation testing has been done and the root cause can be traced to incoming material, it can be difficult to retroactively put this kind of specification in place.
One thing that can be done is to include a check station where the parts and components are brought in to the manufacturing facility so the surface quality can be measured immediately before storage or whatever the first step in the production process may be. This requires a plan for what to do with parts that do not meet the required level of cleanliness. Luckily, when this is done at the forefront of the process, cleaning and treatment operations can be adjusted for this inconsistency.
It can be advisable to require suppliers to perform a cleanliness check before shipping out the components. Ideally the cleanliness tests are done with instruments that are reliable and easy to use. This will most likely involve new negotiations if this new standard wasn’t allowed for in the original contractual agreement. But if that can be put in place, then certainty can be gained that all incoming material surfaces meet a quality standard that makes each ensuing production step more efficient and effective.
Using a quantitative and objective specification on cleanliness and surface chemistry makes sure everyone is on the same page. A reliable evaluation (like contact angle measurements) puts to rest frustrations caused by subjective tests, such as dyne solutions, whose results cannot be reproduced and are functionally inadequate to meet a precise cleanliness guideline. When suppliers and manufacturers share an understanding of surface cleanliness and its importance everyone can be more efficient and produce a better product.
To learn more about controlling the entirety of manufacturing processes to ensure that adhesion and chemical cleanliness are prioritized download the ebook “Predictable Adhesion in Manufacturing Through Process Verification”. Putting specifications on common manufacturing steps that affect adhesion, just like controls that exists to ensure excellence in other areas, creates a process that is more reliable and consistent than ever before.