Printed circuit board assembly in today’s market benefits from highly automated processes. Component sizes have gotten smaller, so placement of components must be more precise.  There is also  a trend toward the use of selective soldering techniques, which allows for precise soldering in different  parts of the Printed Circuit Board Assembly (PCBA) depending on the part size and spacing. Use of surface mount components allows for soldering from a single side using very fine solder pitches, down to 0.4 mm.  These advances necessitate a degree of automation from the feeding of raw boards and components at the front end all the way to Automated Optical Inspection at the back end.  This sophistication results in a high value per square mm of real estate on the board, while at the same time, the degree of automation ensures very high yields.

RUGGEDIZING PCBA’S

The investment in automation also allows for the economical production of PCBAs for the small to medium sized user of PCBAs.  Often, these assemblies will go into industrial, machining, and control applications, which can see exposure to chemicals, dust, electromagnetic interference, shock and vibration.  As a result it is not uncommon for PCBAs to require a degree of ruggedization.  RiverSide Integrated Solutions (RIS) has invested in a multi-system approach that allows us to tailor the degree of ruggedization to the application, providing an appropriate level of protection in the vulnerable areas of the board assembly. Among our capabilities are:

  • Special Application Equipment (Robotic dispensing systems)
  • Conformal coating (Silicone, Urethane)
  • Potting (Epoxy, Polyurethane, and Silicone)
  • Low-pressure molding technology
  • 3D Printing

DEGREES OF RUGGEDIZATION

Most PCBAs can benefit from some degree of ruggedization. Imagining not only the intended application, but all the steps that the board will go through; from shipment to unboxing, assembly and connection.  Taking all of that into account, it may make sense to opt for at least a basic protection against the potential for moisture intrusion.  This is usually provided by a spray-on silicone conformal coating on both sides of the board. The result is a very thin waterproof layer that fills in all of the little gaps between the board components and the board itself, dramatically reducing the probability of moisture intrusion and corrosion.  Conformal coating is usually one of the simplest protections to apply while affording a much improved protection against the elements.

STEP IT UP A NOTCH

If the intended operation of the PCBA includes exposure to temperature extremes, dust, dirt, chemicals, vibration or water, then a higher level of protection is likely required.  This next higher level is usually called either encapsulation or potting. Though the terms are often used interchangeably, in general, encapsulation is less extensive, intended to protect specific areas of the board with a fairly rugged silicone or acrylic.  One common use for encapsulation is protection of specific components.  Especially if they are large, then they are vulnerable to shock and vibration and localized protection of these “heavy” components ensures that they can withstand higher levels of shock.  RIS offers both silicone and urethane encapsulation for PCBs that we manufacture.  For efficient use of these materials we use a weight monitoring system to ensure the correct amount of encapsulant has been dispensed.  These materials can be heat-cured or even UV-cured and are stable and inert.

THE NEXT LEVEL

If we take the step up from an encapsulant to potting; this usually implies a large area up to and including the whole board. The purpose of potting is generally to completely seal the electronics against extremes of exposure. In an agricultural application for example, equipment could be working in the hot sun all day with dust and chemical exposure.  At the end of the day, it may undergo a high pressure washdown.  This would be a typical use case for a potted board.  It is common also for marine use to require potted PCBAs due to the obvious continuous exposure to wet environments.  Potting compounds are often two-part epoxies which may undergo a heat cure.

SPECIAL CONSIDERATIONS

So far we’ve introduced conformal coating, encapsulation, and potting with various silicones and/or epoxies to add degrees of ruggedness to electronic boards.  Some PCBAs have hybrid connections (both solder and wire bond).  In those cases, it is important to protect the wire bonds, since they can be very fragile.  The most common approach is to use silicone as an encapsulant to stabilize the bonds and reduce any stresses between the chip and the bonding posts.

A unique capability we offer at RIS is the ability to use a hot-melt extruded filament under robotic control.A unique capability we offer at RIS is the ability to use a hot-melt extruded filament under robotic control, very much like a 3D printer.  This technique was developed to be able to add vibration and shock resistance to specific areas of the board very precisely.

One final element worth mentioning, though it is related to ruggedness in a more peripheral way, is the use of 3D printed tooling.  Oftentimes board space is at a premium.  The solution is to place components as close together as possible, but without interference.  Along with this, the spacing has to be adequate to allow any encapsulants to flow.  RIS has developed 3D fixturing that does the job.  By taking time to produce custom fixturing, it allows for tighter designs without compromising any ruggedized areas.

Low pressure molding is another protective process. As the name implies it consists of molding a plastic coating around the PCBA to completely enclose the components and thereby protect the completed assembly. This molding process is done within the range of 30 to 300 PSI.

PUTTING IT ALL TOGETHER

Not many contract manufacturers have made the commitment to automate PCB assembly for delivery to the small-to-medium sized operator as RiverSide has.  RIS has thoughtfully added automation, inspection and manufacturing controls to our processes, where they will have the greatest impact.  This benefits the quality of the product and improves yields.  We also have the experience to advise your design team when some degree of ruggedizing will benefit your designs.

About RIS

RIS is an advanced contract manufacturer providing robust solutions in circuit board assembly, product assembly, kitting, supply chain management, fulfillment, distribution, and reverse logistics. We employ more than 300 people and provide services to OEM’s across the world. We operate 3 state-of-the-art manufacturing facilities within the U.S, and as your one-stop-shop we have the capabilities, capacity, quality assurance standards, and resources to provide you with support for all of your manufacturing needs.

With all of the choices in contract manufacturers out there, we know it can be difficult to find someone that not only understands your business model but also has your best intentions in mind. RIS has proven to always be a win-win focused relationship. As your one-stop-shop, we have the capabilities, capacity, quality assurance standards, and resources to provide you with support for all of your manufacturing needs. We understand that supply chain management is difficult and very time consuming, so we urge our customers to utilize us in the fullest capacity. Our total-package solutions include:

· Extensive supply-chain network

· Purchasing and inventory management

· Dedicated Program Manager

· Warehousing and drop-shipping capabilities

· Flexible order fulfillment

· Product assembly: sub-assembly and full product

· Scalability to meet your needs

Contact us today at (507) 523-3220 to see how we can help with your manufacturing project, or click here for a quote.

Summary
Comparing Conformal Coating vs. Potting/Encapsulation
Article Name
Comparing Conformal Coating vs. Potting/Encapsulation
Description
Conformal coating and encapsulation are elements of ruggedizing, applied to Printed Circuit Board Assemblies. Utilizing these and other techniques can ensure long life of the electronic boards in harsh environments.