Designing Products for Ingress Protection

desert road

When a product will be used in a dusty or wet environment it is critical to define the necessary protection needed for the product to function safely and properly.

One common international standard used for this purpose is IEC 60529, which defines a product’s environmental ingress protection in a two-digit numbering system, for example, “IP54.” The first number after the IP moniker represents the product’s protection level against solid objects, including dust. The second number represents the protection level against the ingress of liquids. Generally, as the numbers increase, so does the corresponding level of ingress protection (as seen in the tables below). In the example case, an IP54 rating for a product means that the product is designed with protection from a dust level that would impair safety or function, and from any harmful effects from water splashing on it from all directions.

IP ratings
Full IP ratings guide, credit iec.ch

IP Design Considerations

A higher IP rating will typically drive higher development costs for design and verification. Higher IP ratings can also drive higher manufactured product costs because of tighter tolerance requirements and more stringent quality control required to maintain the rated protection. Therefore, it is important to select the appropriate ingress protection rating based on the intended use cases for the product.

Once the desired ingress protection is understood, engineers can begin developing concepts to meet those requirements. More modest protection ratings can often be achieved by simple design features such as overlapping walls or foam gaskets. The more common challenges of IP55 and above require more involved engineering solutions and a balance of trade-offs between size, cost, and functionality.

Engineers at Porticos have solved these challenges by employing a variety of sealing strategies, depending on product requirements. These solutions have included: liquid adhesives, tape adhesives, off-the-shelf seals like o-rings and molded or flat gaskets, and custom-designed elastomer seals. Each method has its own advantages and trade-offs. The engineer must factor in many considerations in selecting the right solution for each unique product, including efficacy, cost, complexity, size, manufacturability, serviceability, storage, etc. In complex products with various ingress challenges, it is not uncommon to see a combination of multiple ingress protection solutions.

The table below highlights a few of the common sealing strategies paired with the sealing applications they are typically employed to address.

Ingress Protection SolutionApplications
Foam (i.e. Poron)
  • Products with lower IP ratings that require limited water and dust ingress protection
Liquid Adhesive
  • Products with space limitations
  • Lower cost or stable products where rework is not necessary
Adhesive Tapes (i.e. VHB)
  • Products with relatively flat mating surfaces
  • Lower cost or stable products where rework is not necessary
Off-the-Shelf Seals (i.e. o-rings)
  • Products that require servicing that can fit a standard gland geometry
  • Product development that prefers to avoid up front mold construction costs and time
Custom Elastomers
  • Products that require servicing that can’t fit a standard gland geometry
  • Products requiring greater control of geometry, material, and durometer
  • When looking to include additional features to aid in assembly or functionality
  • When included in an already over molded part

Real-World Examples of Sealing Solutions

Shown below are some examples of actual product sealing solutions that have been designed and developed by Porticos engineers and put into production service by clients.

Liquid Adhesive (orange) used to attach and seal two housings (IP67)
Liquid Adhesive (orange) used to attach and seal two housings (IP67).

Dispensed Sealing Adhesive

When a product needs a high level of ingress protection but has very limited space available for a sealing solution, a dispensed liquid adhesive can be a good choice. This solution is effective when the product will not need to be opened regularly for service.

In this case, Porticos engineers were able to use liquid adhesive to eliminate fasteners and provide a clean cosmetic appearance while still achieving IP67 on a small body-worn sensor (40 mm x 50 mm x 11 mm). With so many adhesives to choose from, it is important to understand trade-offs and select the right option to balance viscosity, strength, working time, and cure time. It is also important to use a precision dispensing system to deposit the correct amount of adhesive for consistent results.

Adhesive Tapes

VHB or other adhesive tape is a common method to create a seal on a large flat surface. Typical applications for this sealing strategy include display lenses, membrane switches, buttons, and labels covering exposed screws or other potential entry ports for liquid or dust ingress.

Below are a few examples of these types of sealing solutions deployed by Porticos.

Membrane switches
Membrane switches adhered to cover from the outside with flex circuit tail thru a hole in the cover. (IP65)
Label over screw
Label applied over screw to provide ingress protection and tamper evidence. (IP65)
Polycarbonate lens
Polycarbonate lens with VHB (yellow) installed from the outside and display installed from the inside. (IP68)

O-Ring Seals

O-rings and other off-the-shelf compression seals are commonly used for protection against liquid ingress because they can be affordable and reliable in the right applications. O-Rings seals can be used as a radial or face seal, depending on the space and tolerance constraints of the case design. With a radial seal, the force to compress the o-ring is provided by the walls of the casing parts sliding near each other during assembly, with an o-ring sandwiched between them. The force used to maintain compression of the seal is provided by the strength of the parallel walls. With a face seal, the force required to maintain o-ring compression is provided by fasteners (usually screws) which hold the sealing surfaces the correct distance from each other to maintain the seal. In this case, fasteners must be spaced appropriately to support the uniform force of the compressed seal. The selection of sealing materials, both type and durometer, is of critical importance in compression sealing strategies.

Below are examples of o-ring sealing solutions deployed by Porticos.

Radial o-ring seal
Cross Section of a radial o-ring seal. The gland is created by three separate injection molded parts to prevent a parting line on the sealing surface. (IP68)
Cross Section of two face o-ring seals. The glands are created by two injection molded parts, and the compression is determined by the height of the mating bosses and held by screw forces. (IP65)

Custom Seals

As with o-rings sealing, similar compression considerations are followed when designing custom seals and glands. A custom seal or gland must be designed for consistent compression to achieve the designed sealing performance. However, a custom seal is designed to work with unique and usually more complex sealing surfaces. These custom seals may be stand-alone molded parts that fit between sealing surfaces, or they can be integrated into the larger casing components as an over-mold of a softer compression material.

Below are a few examples of custom sealing solutions designed and deployed by Porticos.

Custom silicon button with seal
Cross section of a custom silicone button with an integrated radial seal. The plastic retainer provides support behind the seal and retains the button with plastic snaps. The rigid plastic center provides good tactile feedback to the snap dome below. (IP68)
Custom Seal 1
Custom seal with rectangular cross section accommodates assembly tolerances without the added space needed by a round profile. (IP68)
Integrated radial seal
Cross Section of Silicone Light Pipe with integrated radial seal. (IP65)
Custom silicone face seal for a speaker
Custom silicone face seal for a speaker. Fasteners around the perimeter were necessary to evenly compress the seal and oppose the water pressure during immersion. The custom design allowed for interlocking with the speaker and two smaller sealing contact faces to reduce the force needed to compress the seal. (IP68)

Conclusion

Depending on their intended use, products often require protection from the ingress of liquids, solids, and dust. It is incumbent upon the engineer designing the product to determine the minimum appropriate strategy to meet a product’s IPxx sealing requirement. Developing and implementing the best strategy is dependent on the complexity and size of the product, the environmental use and life expectancy of the product, as well as the cost and reliability considerations of available solutions.

Porticos has a two-decade-long track record of meeting IP sealing challenges with innovative and effective design solutions. Contact us whenever a need arises to design for a sealing challenge, or even to help with an existing product that needs improved IP protection.

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About Porticos

A WORLD OF OPTIMIZED PRODUCTS

About Porticos — Porticos, Inc. is a mechanical engineering and product design development company located in Research Triangle Park, NC.

Established in 2003, Porticos continues to produce innovative and effective solutions for its clients and the markets they serve. Porticos, Inc. provides mechanical design, analysis, research, and development services to clients including Dell, Motorola, Raytheon, and many others.