Why your EMS partner is your best friend and safest bet when manufacturing electronics for hostile and hazardous environments

John Johnson, NPI Director, Chemigraphic

 

We all rely on electronic products

Imagine your life without your smartphone and you’ll realise just how much we all depend on our electronic products these days.

And – shock, horror! – if you’ve ever had the misfortune to watch your beloved mobile slip into a sink full of soapy water or drop into a pan of hot gravy, you’ll be painfully aware that electronics and harsh conditions do not mix well.

Those intricate electronic circuits are very quick to malfunction under the slightest variance to their usual operating conditions.

Yet, there are many industries that rely on electronic products to operate in places where the environment is too hostile or hazardous for even humans to venture – take deep-sea oil exploration, for example.

Others need products that can withstand extreme shocks, such as devices designed for aviation or military use.

And often products are destined for use in extremely sensitive and potentially explosive atmospheres, like those found in mines.

Electronic products are regularly called on to act reliably in many hostile or dangerous conditions. These place the risks posed by the bubbly contents of your sink and gloopy contents of your saucepan to shame.

They include environments with:

  • Extreme temperatures, both hot and cold
  • Severe temperature fluctuations
  • Dust-filled air
  • Explosive conditions
  • Excess moisture or salty water
  • Jolts, vibrations and regular or continuous impact
  • Sudden power surges

 

When it comes to extreme circumstances your EMS partner is your best friend

How can electronic products be produced to withstand these challenging and dangerous situations?

The requirements of hostile or hazardous environments add multiple layers of complexity to the manufacturing process.

Yet, your EMS partner can help you design and purpose-build devices to specifically operate in many different conditions.

It requires the application of specialist techniques and processes throughout the product’s design and manufacture.

 

Beneath the waves

The marine industry and oil research facilities need sub-sea rovers and maintenance machinery to operate deep in the briny depths.

Many of these products are operated remotely, so they must be incredibly robust to reliably withstand the sub-sea conditions. The physical challenges faced include the constant threat of erosion by salt and the immense force of the water.

Salt is extremely corrosive. It will eat through metal components and casings if specialist coatings and sacrificial layers are not applied to the product structures and circuitry to protect against this.

Conformal coatings act as a protective varnish for circuit components and casings. These coatings are best applied via robotic, automated processes to increase cost-effectiveness, precision and consistency.

Encapsulation of circuitry provides an extra level of protection for the components, effectively closing them off from external elements.

 

Conformal coatings

Conformal coatings are not just used for underwater protection: printed circuit boards are often dipped in coatings to protect them from moisture, heat and dust particles.

There are several types of these thin layers of polymeric film that can be used – but each has its pros and cons.

Depending on the environment in which the product is to be used your EMS partner may suggest:

  • Urethane resin
    Good chemical, humidity and mechanical wear resistance
  • Epoxy resin
    Excellent performance in harsh environments with good abrasion, moisture and chemical resistance
  • Silicone resin
    Performs well in extreme temperatures and has good corrosion and chemical resistance
  • Parylene
    Best performing of all coatings but not suited to extended exposure outdoors

Explosive situations

Products which are designed for use in areas contaminated with toxic substances or carbon dust have to be manufactured to withstand contact with these particles.

Your EMS partner must ensure that all ‘critical parts’ are correct to specification. Faulty circuitry can create an over-current – and the resultant overheating increases the risk of explosion.

It is essential that the supplier of every single component part has been vetted and validated. Every single part must be 100% reputable and offer guaranteed batch traceability.

Relying on reputation alone, however, is not enough. Goods inward inspection criteria must use enhanced checks and measurements, rather than trust visual confirmations. It will also be necessary to employ batch segregation for any mixed stock received.

Impeccable material control governance will be used to ensure that each part is fitted into the correct location. This is not as simple as it sounds: the vast majority of small footprint SMT components lack markings but are visually identical, and over 500 distinct parts can be used in a single printed circuit board.

To handle these complexities, we use barcoding and intelligent materials tracking, such as RFID enabling and automated kitting. These techniques remove the very real possibility of human error when handling such sensitive products.

Further checks must be made after fitting for final verification. Once again inspection by a human is far too prone to error for this operation – and highly unlikely to be sustainable over such a high volume of parts. Automated optical inspection is absolutely necessary.

 

The shock factor

The sheer thrust of acceleration created by rocket-propelled devices requires careful component selection in order to ensure the device is sufficiently robust to survive the shock of take-off. This is especially true for devices with motion potential, such as gyroscopes, valves and actuators.

Your EMS partner can ensure optimal assembly integrity, starting from the bare PCB’s rigidity. Here thickness and copper weight must be balanced against payload constraints. It’s a delicate balancing act, and often to pull it off additional bracing from bonded layers, struts and multiple restraint points will be needed to provide the requisite strength.

 

Rough and rugged

Electronic products that are designed for harsh conditions are often referred to as rugged. There are actually four categories of rugged electronics:

  1. Commercial grade
  2. Durable
  3. Semi-rugged
  4. Fully-rugged

It’s important to realise that ‘ruggedising’ entails a lot more than simply slapping a sturdy case around the usual configuration of components. As already highlighted, many critical decisions will have already taken place at component choice and fixing stage, well before a case is even considered.

Fully-rugged computers, for example, are designed to withstand elements that would fry most PC circuitry or shock it out of any semblance of working order. US military grade computers must achieve MIL-STD-810G, as rigorous a testing requirement as the most severe drill sergeant ever offered his troops.

To manufacture suitable housings there are a variety of plastics available. These include acrylonitrile butadiene styrene (ABS), polycarbonate, polyphenylsulfone (PPSU), ultra-high molecular weight polyethylene (UHMW) and nylon. These tough materials can be used in combination to increase impact resistance, and elasometric polymers can also be added to deform during impact and reform after.

 

When the heat is on or the big chill hits

In extreme temperatures solder integrity is absolutely critical. What’s more, this base process must not only be robust but repeatable.

While intelligent automation offers an ideal way to ensure consistency, the intelligence here comes not from the machine itself, but from the knowledge and expertise of the EMS partner’s engineering teams who must establish its operating criteria.

 

Explosive environments and intrinsic safety

It is usual for electrical equipment to create tiny electric arcs and to generate heat. Under normal circumstances this presents no problems, but where there is a concentration of flammable gases or dust, such as petrochemical refineries and mines, this can become an explosive ignition source.

Intrinsic safety (IS) is a certified technique to protect against this and ensure that electrical equipment can operate safely in hazardous areas. It does this by limiting the electrical and thermal energy in the device.

An example of where this is required is marine transfer operations involving flammable products. During the transfer from marine terminal to tankers it is vital that two-way radio communication is maintained in case of an incident. To enable this the radios used must be certified as intrinsically safe.

There are actually many other ways to make equipment safe for use in explosive-hazardous areas. These include using explosion- or flame-proof enclosures, encapsulation, sealing, oil immersion, venting, powder/sand filling and dust ignition protection. However, intrinsic safety is the only realistic method to use for handheld devices.

 

On the record

Accountability and documentation are particularly critical when developing products for harsh and hazardous environments. As so many complex conditions and procedures are involved, it’s essential that every step is prepared, researched and accounted for.

Your EMS partner will ensure that the documentation and certification you need are easily accessible at all times. And you’ll certainly be needing this evidence trail to demonstrate continuous control and traceable processes which form the basis for evidence of compliance to industry standards and regulatory requirements.

 

The true value of your EMS partner when manufacturing for harsh environments

Understanding the complex regulations, industry standards and latest best practices involved in making devices safe for use in different conditions is one way your EMS partner can be your best friend and safest bet.

By suggesting other, or complementary methods, they can ensure that your design is suitable not only for manufacture and regional or industry-specific requirements, but also for its intended end use.

With an increasingly complex and ever-changing supply chain they also act as your eyes and ears in ensuring that components used are exactly as required.

And through robust and rigorous checks they can ensure that the final product is 100% fit for purpose and for the environment it will be used in. Even if this environment is the kitchen sink or a bubbling pan of gravy and the product is your mobile!

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