Indoor growing technology has been rapidly improving in recent years, increasing in sophistication and effectiveness. This is driven by the demand of a rapidly increasing indoor farming market, which requires greater and greater output efficiencies. The indoor farming market is forecasted to grow 10.9% per year from 2021 to 2028, going from $36.4B to $75.3B (US) [1]. This has created challenges as electronic devices are expected to perform flawlessly for years is the harshest of conditions.
Growing Technology for Indoor Farming
The introduction of robotics in agriculture has enormously increased the productivity of indoor farms. Robots can pursue various operations, from lifting heavy weights to the most complex tasks, like visually checking the maturity of the crops ready for harvest using machine learning algorithms.
Spraying robots within enhanced and automated movable versions of aeroponics systems significantly impact the efficiency of indoor growing. Spraying robots use specific nozzles to irrigate the plants, producing micro water particles that are readily absorbed by the plant's roots. Their application significantly reducereduces the water consumption in the growing area and consequently lower the growing costs [2].
LED grow lights are another important technology for indoor farming. Manufacturers focus on engineering grow lights with the ideal light intensity and spectrum for particular crop species, optimizing plant yields, size, number of leaves, and even flavor.
The goal is to to achieve the highest photosynthetic photon flux (PPF) while minimizing the required power consumption of the grow light. Even with optimal PPF of the growing lights, two other parameters need to be adjusted to maximize the photosynthesis process: the artificial CO2 addition and increased temperatures. Increased environmental temperature adds additional challenges to the reliability of indoor farming electronic devices.
Chemically Induced Corrosion in High-Temperature Environments
Whether growers are using soil-based or soilless hydroponic growing systems, they will face the same issue. Both solid-based and liquid-based fertilizers tend to readily evaporate into the atmosphere in high-temperature environments. Most fertilizers are based on nitrogen, potassium, and phosphorus compounds, and only the last two are non-corrosive.
Potassium hydroxide is an unavoidable compound for the fertilization of every plant, especially in the flowering stage. This compound is very corrosive to metals. On the other hand, nitrogen-based compounds, which are needed for vegetational development, react with waterwater, and tend to vaporize. As a result, they form highly corrosive nitric gases that penetrate through LED encapsulation and attack the metal in the inner side.
High-Moisture Indoor Environment Challenges
The high humidity environment is standard for cannabis growers, and it evolves in the flowering stage. It is induced by a high transpiration rate where plants release water through their leaves, so it is common for many other crops.
SoSo, what are the common problems for all high-humidity environments? First, the potential for fungal diseases, which all growers fear because they can ruin their yields. Second, corrosion can permanently damage indoor electronics, affecting lighting efficiency and performance.
Impact of Corrosion on the Functional Life of Electronics in Indoor Farms
Lead-based and lead-free solders containing tin, commonly used on printed circuit boards (PCBs) of grow lights, robotic systems, and control systems, are susceptible to corrosion. Regardless of tin's corrosion resistance to moisture, it can't withstand the influence of nitric acid or potassium hydroxide, which are strong oxidizing agents [3].
Those agents can etch into solder joints that bond electronic components to the board. The result is a weakening of connections between leads of the surface-mounted components and contacts on the PCB. That scenario can cause numerous issues, the least painful being a broken circuit. In that case, the electronics stop functioning and have tomust be repaired or replaced. This can result in a drop in crop yields and customer dissatisfaction in the electronic device supplier. That’s bad, of course, but it could be worse.
In another likely scenario, the poor connection affects the current intensity that passes through LEDs or the selectivity of the wavelengths that will be emitted. The poor connection can be caused by copper corrosion as well. Although copper has some corrosion resistance against moisture and various chemicals, it can't resist corrosion for a long period time.
As a result of corrosion, the light intensity emitted by LEDs will be lesser than desired. The difference might be undetectable by the naked eye, but still could reduce yield significantly. In another case, emitted colors could shift from target ones. Again, this might not be noticeable by growers, but yields, plant size, leaf count, and even flavor could be noticeably affected. SoSo, in these scenarios, whole growing cycles can pass without corrosion in the LED grow light electronics being detected. Late detection of a problem is inevitably more costly.
The greatest service life issue with indoor formingfarming robots is their constant and direct contact with tiny water droplets. The constant exposure to moisture leads to an increased rate of corrosion reaction, which makes them more vulnerable. Since robotic systems are highly complex, the slightest change in their operation could cause immeasurable losses, especially in commercial facilities.
Corrosion prevention is an essential activity that enables durability and long lifetime of all electronics in indoor farms. While electronics in robotic and control systems are generally accessible for repair and preventative maintenance, most LED grow lights are impractical to repair. Preventative measures need to be taken at the point of manufacture of the electronic systems to ruggedize them enough to better survive the rigors of indoor formingfarming.
PCB Water Resistance from Conformal Coatings
The manufacturer of grow lights, robotic systems, and control systems can take steps to increase the water resistance of their electronics. There are several strategies that can be implemented to ensure grow light reliability:
- Sealed packaging / gasketing – All grow lights are packaged with the goal of keeping outside contamination from reaching internal electronics. In reality, it is nearly impossible to keep moisture from working its way in 100% time, and still have a device that is economical to assemble and service.
- Encapsulates (potting compounds) – Another strategy is to fully submerge sensitive electronics into an epoxy resin. That eliminates any possibility of rework or servicing once the PCBA is potted, but it will be water-proofwaterproof. One concern is the encapsulate over the LED could dim the light and potentially shift the color. It would also make dissipation of heat problematic, which could drastically reduce the life of the LEDs. In LED grow light manufacturing, epoxy encapsulation eliminates the possible of reworking a damaged board or failed LED, which might only require minor repairs. Without the ability to repair, the only alternative is scrapping a complete panel of expensive LEDs.
- Conformal coatings – Rather than submerge the circuit board into a thick layer of resin, a resin layer can be applied that “conforms” to the surfaces of the board and components. Conformal coatings are generally thin enough to allow for adequate thermal dissipation, and unlike encapsulates, they can be removed for rework and repair of the LED grow lights. While not as water-proofwaterproof as potting compound, conformal coating can provide enough water-resistant protection when used in conjunction with sealed packaging.
Techspray offers numerous conformal coatings that include features to match the specific environments of indoor farms. Namely, the coating formulations are specifically made according to needed protection, whether thermal, chemical, moisture, or static resistance.
For electronics in the indoor farm, the aggressive compounds in high moisture environments present the greatest threat. Silicone conformal coatings are the best choice for indoor farm electronics since they provide excellent chemical and moisture resistance. As a result, their application permanently protects the PCBs and all other electronics prone to corrosion, ensuring their durability in harsh environmensenvironments.
Techspray developed Fine-L-Kote™ LED2 specifically for light-emitting diode (LED) applications. This coating is completely transparent, meaning it does not interfere with light wavelength or intensity, which is a particular concern of all growers. Also, this coating is hydrolytically stable and retains its physical and electrical properties even after high humidity exposure for extended periods. The last feature, which should be pointed out, is its flexibility and resistance to extreme temperatures, which is particularly important on the flexible and rigid circuit boards found in LED grow lights.
Importance of Printed Circuit Board (PCB) Cleaning
Most modern PCBs are soldered using no-clean flux to avoid the necessity of a cleaning process. For electronics used in extreme environments like indoor farms, cleaning becomes more important in the electronic assembly process, even for no-clean fluxes.
If there is any ionic residue on the PCBA, like flux residue from the soldering process, moisture and current can lead to dendritic growth. Dendrites are conductive branches that literally grow from one contact point to another, leading to current leakage or short circuit.
In addition, cleaning electronics is all the moremore important before applying conformal coating. Improper cleaning or lack of cleaning [RM1] is a common cause of conformal coating defects like fish eyes, dewetting, and delamination. These defects open up entry points for moisture and chemicals, increasing the chance of corrosion issues. For more information on conformal coating defects, check out https://www.techspray.com/how-to-identify-and-cure-the-top-7-conformal-coating-defects.
Flux removers (defluxers) remove flux residues and other contaminants left by manufacture, rework, or repair of printed circuit boards. Residues from higher, lead-free temperatures are more baked on and harder to clean. PWR-4™, G3®, E-LINE™ and Precision-V™ flux removers have been proven very effective at removing fluxes baked on at lead-free temperatures.
Micro-components and fine pitch leads are delicate and easily damaged, so brushing and scrubbing should be avoided if possible. Both G3, E-LINE and Precision-V have a powerful spray and strong solvent that blasts off residues and cleans areas under components that a brush cannot touch.
Techspray offers traditional solvent-based cleaners and cutting-edge water-based technologies marketed under the Techspray Renew™ brand. Techspray Renew branded cleaners are innovative solutions that combine the best of current “green” technologies to make the most powerful eco-friendly cleaners on the market.
Tecshpray Conformal Coatings & Flux Removers
Engineering electronics for the extreme environments of indoor farming is challenging, but important to avoid negative impacts on crop yield and quality. Conformal coating and PCB cleaning is critical to ensure the long service life of grow lights, robotic systems, and control systems. For more information, contact a Techspray application specialist at 678-819-1408 or info@itwcce.com.
References
1. Indoor Farming Market Size, Share & Trends Analysis Report By Facility Type (Greenhouses, Vertical Farms), By Component (Hardware, Software), By Crop Category, By Region, And Segment Forecasts, 2021 – 2028
2. Imran Ali Lakhiar and Jianmin Gao and Tabinda Naz Syed and Farman Ali Chandio and Noman Ali Buttar. (2018) Modern plant cultivation technologies in agriculture under controlled environment: a review on aeroponics, Journal of Plant Interactions, Vol. 13,338-352.
3. Mori, Masato & Miura, Kazuma & Sasaki, Takeshi & Ohtsuka, Toshiaki. (2002). Corrosion of tin alloys in sulfuric and nitric acids. Corrosion Science - CORROS SCI. 44. 887-898. 10.1016/S0010-938X(01)00094-4.
