Avoiding voids in potting applications

Paul Whitehead, strategic accounts manager at Intertronics, explains how manufacturers can avoid the introduction of voids during the processing of potting compounds.

Trapped air or voids can cause failures in electronics assemblies. Voids can subvert the purpose of the potting or encapsulating polymer, by compromising thermal conductivity and heat dissipation, or the electrical insulation properties. Voids and delamination provide pathways for moisture or other contaminants and weaken its physical structure, allowing greater susceptibility to damage or cracking.

Formulators of potting materials for electronics applications are careful not to supply products with entrapped air.  Consequently, entrapped air is usually a processing issue.

Correct storage is important in ensuring that the compounds do not absorb moisture. Some chemistries are hygroscopic and readily absorb moisture from the air, which reacts to form a gas. They are packaged in airtight containers and/or with desiccants. Taking care in handling the materials in accordance with the manufacturer’s recommendations can prevent problems later.

Non-contact methods of mixing, such as planetary centrifugal mixers or automated metering and mixing systems, typically introduce less air than other mixing methods. If using metering and mixing equipment, ensure this is regularly maintained and avoid introducing air during replenishing. If air inclusion from mixing is unavoidable, then you should consider removal via degassing.

Low viscosity materials may be able to adequately degas themselves. For best results, use a container with a large surface area and shallow depth and scoop off any bubbles that rise to the top and remain. For higher viscosity products, or where production time doesn’t allow for unaided degassing, vacuum can expedite the process. If the mixed working life is sufficient, vacuum chambers may be used for degassing. Avoid using excessive vacuum, as some constituents can be volatile and will evaporate at lower pressure, altering the material’s formulation.

Centrifugal force can also be used to degas the material before application. In practice, we often see this when using a planetary centrifugal mixer, which mixes and degasses plural component materials of multiple viscosities, and also powders. The non-contact mixing action (revolution and rotation) does not add air, instead it tends to remove it. An additional ‘defoaming’ mode applies a more direct centrifugal force to the mixed materials, separating out the air. Care must be taken not to separate any fillers or heavier constituents with the centrifugal action.

For critical applications, these planetary centrifugal mixers can be configured so mixing happens under vacuum. Many of our customers have seen success with the THINKY ARV-310 Mixing and Vacuum Degassing Machine.

Application methods

Once the compounds are mixed, it is important not to introduce or entrap air during application. Techniques to eliminate or minimise air bubbles in the completed assembly include pouring or injecting in stages, driving out air rather than trapping it under components. Tilting the assembly, filling from the bottom and perhaps preheating to reduce viscosity and surface tension can help.

In critical applications that are geometrically challenging, potting can be done under vacuum, or the potted unit can be vacuum degassed before cure. Another tactic is to place potted parts onto a vibrating table, helping to release trapped air.

Pressurised feed systems can also saturate the material with dissolved air, which can result in bubbles later on. It is good practice to depressurise systems when inactive, and to use only the required pressure. Alternatively, this can be avoided by having a barrier between the compressed air and the potting compound, or by using a pump.

Contamination and cure

The uncured potting compound or encapsulant can react with contaminants, potentially causing a lack of adhesion and subsequent delamination, or the formulation of gas bubbles, both of which cause voids. Contamination issues can be resolved by using cleaned and dried assemblies.

Shrinkage of the compound during cure may create voids in parts of the assembly. Again, applying the materials in stages can minimise this by allowing the materials to fill any gaps left by the shrinkage.

Avoiding voids in PCBs is essential for the final assembly’s performance. By carefully considering each stage of their potting process, manufacturers can avoid voids and create parts with reliability and longevity.


Station Field Industrial Estate
Banbury Road

+44 (0)1865 842842



More products
23 hours ago
Young designers take off with e-racing cars and support from norelem
Set around the challenge to build and operate a purely electric racing car, this year’s Formula Student (Electric) competition put student designers to the test. To prepare several teams for the event, the VDI Racing Camp powered by norelem brought together more than 250 participants from across Germany, preparing them for the prestigious competition by providing components and support to each team.
1 day ago
Showcasing design, production and process engineering in the food and drink sect
Taking place on 1 May 2024 at the National Motorcycle Museum, Food Manufacturing Live serves the design, production, process and maintenance engineering teams across the UK food and drink manufacturing sector.
4 days ago
WDS reinforces Core Values for ultimate customer experience
WDS Components continues to strengthen its commitment to customers, including optimised stock availability and delivery, as well as ensuring quality throughout the entire customer journey. Now the Leeds manufacturer and supplier of standard parts and components has underpinned its customer assurance with the re-energising of its Core Values.
4 days ago
Essentra makes further progress on sustainability with latest EcoVadis rating
Essentra has been awarded a silver medal by EcoVadis, the global provider of business sustainability ratings, as confirmation of the organisation’s ongoing journey towards a more sustainable future.
1 day ago
WDS Components triumphs at MAKE UK Awards 2023
WDS Components has been named Regional Winner for the “Small Medium Enterprise (SME) of the Year” in the Northeast, Yorkshire and Humberside category at the prestigious MAKE UK Manufacturing Awards 2023.
2 days ago
Learning to weld the easy way
Using the newly available Welducation Simulator from Fronius, welders can learn, train and consolidate their welding skills step-by-step under realistic conditions without any risk to safety and with no additional costs for materials, gases, or wear parts.
22 hours ago
Henkel offers free demonstrations to body shops
Henkel is offering its support to body shops across the country with free in-person demonstrations of LOCTITE and TEROSON products, with the goal of helping them lower costs, improve the quality of repairs and reduce key-to-key times.
1 day ago
Essentra opens new facility in Monterrey to support expansion
Essentra has opened a substantial new manufacturing and distribution hub in Monterrey, Mexico, both to increase production capacity for existing customers in North America, but also to grow its customer base in Mexico and Latin America.
2 days ago
Cees Fasteners announces partnership with Simoni
Cees Fasteners, a privately owned supplier of high quality fastenings, is delighted to announce its partnership in the UK with Italian Brush manufacturer, Simoni.
1 day ago
FDB Online hardware ex-stock for urgent delivery
The FDB says its online store features an extensive range of locks, swinghandles, hinges, handles, sealing gaskets, rod locks, door stays and other enclosure/cabinet accessories – all held in stock for urgent delivery, and come together with the Rocfast lock assembly and logistics service.

Login / Sign up