FEATURE Materials Handling & Conveying


FR-4 board itself, all of which have unique surface energies and chemistries. Without proper adhesion, silicone can begin to delaminate, not only at the edges of the PCB board but also in the form of small air pockets on or around components, leading to moisture ingress and subsequent corrosion or electrical shorts.


“In terms of surface energy, the best strategy is to deposit a thin-fi lm coating over everything so the silicone only has to bond to one surface energy,” says Barden. “A process using plasma can basically harmonise all of the many surfaces and turn it into one.” To accomplish this, PVA TePla has developed a specifi c process starting with a precision cleaning/surface activation treatment followed by the deposition of an inert chemical primer that serves as a tie layer for the over-moulding and provides a uniform surface energy for the silicone to bond.


Plasma treatment expertise Contract processors should ideally bring a combination of resources for plasma R&D and experience with many customer types in markets beyond medical devices. Working with a contract processor also has tremendous advantages when it comes to tapping into the years of technical expertise applying a variety of plasma treatments. This can often signifi cantly hasten research and development eff orts. In many ways, the application of plasma is the domain of chemists and other scientists. Companies like PVA TePla, for example, have on staff three Ph.D. scientists and surface, polymer, physical, bio and organic chemists, as well as engineers, plasma physicists and metallurgists.


“Because we see similarities in the types


of materials being treated, our experience allows us to develop and optimise custom proprietary processes quickly and effi ciently, saving our customers signifi cant time and money in the development phase of product development,” says Barden. An extensive knowledge and experience in manufacturing plasma equipment is also a plus, given that most contract processors just purchase equipment from global providers. Also, with a specifi c background in plasma equipment manufacturing, the contract processor can provide critical insight on validation, production methods, fi xturing, as well as hardware and software modifi cations. Examples include special hardware for batch processing, such as a mass fl ow controller, a diff erent pump confi guration or unique chamber sizes. Additional specifi cations for a process for electronic part, antistatic so when it comes out of the plasma because it’s an electron emitter, it can accumulate static; antistatic fans can be used to remove static on the parts when the chamber is opened.


In some cases, up to 50 times bond strength improvement can be achieved through plasma bonding techniques


Plasma treatments are utilised to increase the surface free energy of the material to be bonded


“Depending on the application and complexity, customers face strict industry requirements and often have unique product of processing requirements,” explains Barden. “Generally, we have existing solutions for most of the things, so usually that is not a concern.” Even the way the parts are delivered to the contract processor, or how they are packaged and returned, can be modifi ed as needed. Parts can be sent in specifi c counts in bags or in specifi cally-designed pre-loaded trays, for example. Once treated, the parts are typically packaged in polyethylene bags, but for customers with electronic devices like PCBs, antistatic bags can be specifi ed to protect components from electrostatic discharge. The company operates nine plasma system lines, allowing a run of three jobs simultaneously. Turnaround time depends on the quantity and complexity of the processing, but it can be quite fast, where a single batch can be completed in an hour, and large batches of, say, 1,500 parts can be treated and shipped within a day or two. For manufacturers interested in treating parts and components with plasma but don’t want to make the investment just yet, or require only small batches, outsourcing to a qualifi ed contract processor could be the perfect solution.


CONTACT:


PVA TePla www.pvateplaamerica.com


automationmagazine.co.uk


Automation | July/August 2021


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