A new White Paper
It is very interesting when two of our suppliers get together and do some work which shows the value that some synergy can bring to understanding our technology. In this case, Dymax (adhesives and curing equipment) and Brighton Science (surface measurement) have produced a white paper called The Science of Bonding: Understanding the Interaction Between Adhesive Chemistry, Processing and Substrate Surfaces to Achieve Optimal Bonding Performance. It is well worth reading.
The paper identifies what it calls the “three pillars” of reliable adhesion:
- Adhesive chemistry
- Process and application control
- Substrate surface energy
If any one of these pillars is weak, inconsistent, or poorly controlled, bond performance suffers.
Focussing on electronics manufacturing, the authors investigated the adhesion performance of four adhesive chemistries: UV curable acrylate, UV curable epoxy, RTV silicone, and two-component epoxy. These were tested on two common substrates, FR-4 and polycarbonate, using four different preparation methods: no preparation, IPA wipe cleaning, plasma treatment, and plasma treatment followed by a 24-hour delay before bonding.
The testing involved measuring water contact angle after surface preparation and then comparing the resulting bond strength in each case.
The results
The results showed a strong overall correlation between lower water contact angle and higher bond strength, particularly for the UV curable systems, where plasma treatment significantly reduced contact angle and produced stronger lap shear results. The study also showed that as plasma-treated surfaces aged and contact angle increased again, bond strength declined measurably. However, the relationship was not identical across all adhesive chemistries. RTV silicone showed only modest improvement despite surface treatment, while the two-component epoxy performed well even on relatively untreated substrates, suggesting greater tolerance to contamination and lower surface energy.
My own takeaway is that water contact angle is a highly useful predictor of bondability and surface readiness, but adhesive chemistry and process conditions still play a major role in final bond performance. It is also worth highlighting how quickly surface activation can decay. In several cases, a 24 hour delay after plasma treatment produced a measurable reduction in bond performance.
Challenge
I am going to challenge a couple of points in the paper.
- “Adhesives often struggle to bond to polymeric surfaces without additional surface treatment.” I do not think this is universally true today. Some substrates remain notoriously difficult to bond reliably, PTFE being the obvious example, but many engineering plastics and even some polyolefins can now be bonded successfully using modern adhesive formulations. We have been supplying adhesives for bonding PC, ABS, PMMA, PA, PET, and similar materials without pre-treatment for decades.
- “…substrate surface variability remains the most persistent cause of inconsistent adhesion, and often the most overlooked.” In my experience, once production starts, process variation often becomes the dominant risk. Our paper Process Validation in Medical Device Bonding: Controlling Variables gives some insight into the large number of process parameters which can drift over time despite best efforts.
Water contact angle
A major theme throughout the paper is the use of water contact angle measurement as a practical process control tool. Rather than relying on assumptions about cleanliness, you can quantitatively assess whether a substrate is genuinely ready for bonding. Surface energy measurement moves adhesion from “experience and hope” toward something much more measurable and repeatable. Brighton Science’s Handheld Surface Analyst delivers fast, precise, and repeatable water contact angle measurements, allowing manufacturers to verify surface condition before critical production steps.
For us, this reflects how modern manufacturing increasingly works in practice. Reliable bonding is no longer just about selecting an adhesive from a datasheet. It requires understanding the interaction between materials, surfaces, dispensing, curing, contamination control, and verification methods. We can help you with that – let’s start by talking about your application.
If you work with electronics assembly, encapsulation, conformal coating, sensor manufacturing, medical devices, or other high-reliability industrial products, this white paper is well worth your time.
