How to Protect a Circuit Board from Moisture?
As you are aware, moisture has the potential to greatly compromise the dependability and durability of your Printed Circuit Boards. A tiny amount of moisture can cause certain problems that harm the performance of your electronics. It is very necessary to ensure that your PCBs are adequately protected from the effects of moisture, bearing in mind that they are in conditions that may expose them to excessive amounts of moisture or water. This post is about the importance of PCB Moisture Protection what affects moisture getting to the boards, and other techniques to identify and avoid moisture as well as effectively remove it.
These principles will assist you in preventing both manufacturing and circuit damage and maximize the PCB’s functionality and durability for new and existing equipment.
Top Ways to Protect Circuit Boards from Damage
Why Protect a Circuit Board from Moisture?
Preventing moisture from accessing the circuit board is critical to retaining the equipment’s reliability, operational capability, and durability. Here are the key reasons why moisture protection is crucial:
Corrosion
The worst enemy of a PCB is moisture because it erodes the metal on the printed circuit board by forming a layer of metal oxide, especially on traces and solder joints, thus making the metal to become weak and the electrical conductivity to become high.
Short Circuits
Water usually acts as a medium, and if it finds its way across the different points on the PCB, it may cause short circuits and lead to device failures.
Electrical Leakage
Humidity affects the performance, resulting in erratic behavior, less efficiency, and more power consumption due to unintentional electrical currents created by moisture.
Insulation Degradation
Humidity also affects the insulating features present in the PCB since it leads to deterioration of these insulating materials thereby increasing the hazards of more electrical shorts and leakages.
Component Damage
Humidity affects components in terms of physical destruction, for example, swelling or separation of PCB layers, which leads to failure.
Fungal and Mold Growth
High humidity supports the growth of funguses and mold, which result in the deterioration of the material and possible electrical problems.
Reliability and Longevity
Moisture protection ensures that electronic devices operate reliably over long periods, even in harsh conditions.
Safety Concerns
Since moisture resistance is critical to ensuring that the durability of service is achieved, its provisions safeguard electronic instruments against early failure, especially when they are applied in hard conditions.
Hygroscopic Expansion
When PCB comes in contact with moisture or water, it undergoes the phenomenon of hygroscopic expansion. It induces mechanical stress in it which disrupts its mechanical integrity by producing microcracks in its internal structure. For this reason, it is required to protect it from moisture by applying barriers made from acrylic material.
Disruption of the Dielectric Constant
High absorption of moisture content from the surroundings disrupts the dielectric constant of PCB. It is because of the reason that moisture has a relatively higher level of dielectric constant as compared to PCB which ultimately increases the value of dielectric constant of PCB. As a result, it alters the signal speed and impedance of the PCB. Thus, it is vital to shield the circuit board from humidity.
Moisture in Air and Heat
Factors Influencing Moisture Penetration of PCB
Numerous factors affect the degree to which moisture can breach a PCB. Thoughtful consideration of these aspects is critical for developing operative protection tactics:
Environmental Conditions
The environment can significantly affect moisture diffusion, where a PCB is used or stored.
- High Humidity: An increased level of humidity is likely to worsen the outer layer of PCB. As a result, it upsurges the penetration of moisture in PCB.
- Temperature Fluctuations: A nonstop and extended variation in temperature enlarges the claps in the PCB and thus intensifies the absorption volume of moisture in the PCB.
- Direct Exposure: Strenuous washing and rain basis the direct contact of high levels of moisture to the PCB.
PCB Design
The choices of the design of PCB impact moisture resistance and growth.
- Component Layout: Inappropriate typography raises the moisture content in PCB.
- Via Placement: Non-strategic placement of vias increases the penetration of moisture in PCB.
- Solder Mask Coverage: Poor quality of coverage increases the penetration of moisture in PCB.
Materials Used
The selection of materials touches on how much moisture a PCB can engross.
- Composition of Materials: Different materials absorb moisture at different rates.
- Solder Mask Material: Moisture penetration highly depends on the quality of materials used.
- Absorbency: Permeable materials can absorb moisture.
Manufacturing Quality
Quality in manufacturing practices affects moisture resistance.
- Curing Processes: Inefficient curing processes increase the penetration of moisture in PCB.
- Contaminants: Contamination can compromise protection.
- Quality Control: Poor quality control increases defects and high levels of moisture in the PCB.
Protective Coatings
Effective coatings are crucial for preventing moisture penetration.
- Type of Coating: The type of Coating offers varying moisture resistance.
- Application of Coating Material: The proper application ensures effectiveness.
- Thickness of Coating: Adequate thickness provides better protection.
Thickness
Different levels of thickness influence the penetration of moisture in PCB.
- Low Thickness: High capillary action in thin materials is because of low thickness which may increase the penetration of moisture
- High Thickness: Low capillary actions in thick materials reduce the penetration capacity of moisture
Thermal Variation
The moisture absorbing capacity of PCB varies with temperature because it induces,
- Higher condensation: Fluctuations in temperatures increase condensation and penetration of moisture
- Expansion and contraction: Temperature variations induce PCB expansion and contraction, leading to higher moisture levels.
- Microcracking: Thermal variations cause microcracking which is responsible for higher moisture penetration in PCB.
Geometry of PCB
Variations in surface area and edges influence the moisture-absorbing power of PCB.
- Surface Area: High absorption of moisture with the large surface area of PCB
- Edges: Beveled edges of PCB decrease the entry of moisture while sharp edges of PCB increase moisture absorption
Modeling PCB Interconnects with Geometry
How to Detect Moisture in PCB?
Detecting moisture in PCBs is critical for early action and harm avoidance. There are several methods for detecting moisture:
Visual Inspection
Visual inspection is the most basic way of detecting dampness. Look for corrosion, discoloration, and water droplets on the PCB. While this method can provide instant information, it is only occasionally effective at identifying interior moisture or subtle symptoms of deterioration.
This method is suitable for detecting physical change and is helpful in the detection of cracking, oxidation, and contamination. Sometimes visual testing finds residues that are deposited due to leakage and other physical changes.
Electrical Testing
Electrical testing entails inspecting the PCB for changes in electrical performance that may indicate the presence of moisture. This includes determining insulating resistance, testing for shorts and openings, and running continuity tests. Electrical abnormalities may indicate moisture-related concerns.
Humidity Indicators
These are devices or materials that, when exposed to moisture or change color, are referred to as humidity indicators. You can place it within electronic enclosures to detect moisture levels. While they do not detect moisture directly in the PCB, they provide information about the humidity levels in the surrounding environment.
Electronic sensors are placed in most of the latest and highly advanced humidity indicators. They show warning signals, notifications, and alarms in response to high levels of moisture content. However, no signal, alarm, or notification is received in the presence of low moisture content in PCB.
Thermal Imaging
Flaws on the PCB surface may reveal temperature characteristics using thermal imaging cameras, and moisture is a potential reason. Moisture can cause thermal anomalies because it affects the thermal conductivity and capacitance of materials.
Dielectric Testing
Dielectric testing determines the dielectric constant of PCB materials. Moisture has a greater dielectric constant than most PCB materials. Hence, an increase in the dielectric constant indicates the presence of moisture.
Moisture Detection Sensors
There are moisture detection sensors intended for moisture detection in electrical and electronic items. These sensors can be implemented directly on the PCB or placed in the device’s housing if any exist. They have combined features, that allow monitoring and generating an alarm in the case of critical moisture levels.
Resistivity Testing
Resistance in PCB is a possible way to detect its moisture content. Ohmmeters are specially designed to check PCB resistance and describe the extent to which PCB resists electrical conductivity. For this reason, a PCB with high moisture content has more resistance as compared to a PCB with a low level of absorbed moisture.
Spectroscopy
As water can absorb Infrared Radiation (IR), so spectroscopy is an excellent method to detect moisture content in PCB. Thus, PCB with high moisture content gives broad and strong peaks in spectroscopy while PCB with low moisture content shows relatively narrow and weak peaks.
Acoustic Emission Testing
The acoustic emission testing detects moisture content in PCB. This method has the potential to identify those defects which are caused by moisture in PCB. If PCB has a higher level of moisture content, strong acoustic signals would be received during the test. However, if PCB has a lower level of moisture content, weak acoustic signals would be received during the test. It is because moisture absorption causes defects and swelling in PCB which causes fluctuations in the emission of acoustic signals during this test.
IPC Class 3 PCB – IPC-A-610 Class 3 PCB Assembly
How to Prevent Moisture in PCBs?
The presence of moisture leads to the failure of the functions on a PCB depending on the part that comes in contact with the moisture. When the PCB is placed in an environment where the atmospheric pressure exceeds the resistance of the PCB then the moisture penetrates the PCB. To avoid moisture exposure in PCBs, there are significant design elements, manufacturing techniques, protection needs, and storage and transport measures.
Design Considerations
The layout, material selection, and designing procedure of the PCB can affect the board’s resistance to the moisture of the PCB. So, protection from moisture should be kept in mind first during the manufacturing of the design of the PCB that has long-term reliability in any environmental condition. Effective PCB design can significantly reduce the risk of moisture penetration. Implementing smart design features ensures better protection against environmental factors.
- Optimize component placement to minimize moisture entrapment.
- Use sealed vias to prevent moisture ingress.
- The internal layers of the PCB can be protected from moisture by proper sealing. Incorporation of the strategic ventilation and features of drainage during the manufacturing of PCB helps to manage the condensation and air buildup within the enclosure.
- The material for the manufacturing of the PCB should be selected that is resistant to moisture, corrosion, and environmental degradation.
- Ensure complete and adequate solder mask coverage. During the manufacturing of the design of the PCB, complete coverage should be ensured with copper traces and pads having high-quality solder masks providing resistance against the intrusion of moisture.
- Applying conformal coatings to shield the PCB is beneficial because applying a protective coating like the coating of acrylic or silicon can create resistance against moisture and a barrier to the environment; a condition causing the moisture of the PCB.
Manufacturing Practices
The following are factors that should be observed to fulfill good manufacturing practices of moisture-resistant PCBs: Some techniques can help eliminate the formation of defects that can lead to moisture penetration.
- Ensure proper curing of solder masks and coatings.
- Maintain a clean manufacturing environment to avoid contamination as the environmental control and monitoring strategies can enhance the protection of the PCB.
- The implementation of sensors and monitoring systems for tracking the temperature, humidity, and other environmental factors helps to mitigate the potential issue to the surface of the PCB.
- Incorporation of the system of dehumidification or utilization of the desiccant material for removing the excess moisture prevents the PCB from the track of moisture.
- Control humidity levels in the manufacturing facility. Employing the heating elements and fans for maintaining the constant airflow can reduce the formation of condensation.
- Use high-quality materials with low moisture absorption.
Protective Measures
Applying protective measures can provide an extra layer of defense against moisture. These measures can significantly enhance the durability of the PCB.
- coverings like acrylic, silicone, or polyurethane provide resistance against moisture to PCB.
- Compress delicate components or the whole PCB. For the manufacturing of the PCB layer should be manufactured that can regulate the temperature.
- Implementation of the desiccant material and absorbing moisture materials from the air.
- Individuals should wear protective gloves to prevent the PCB from contamination involved in the process of manufacturing the limitation process of PCB.
- Employ sealed enclosures to protect against environmental conditions.
- Use moisture-resistant materials in PCB construction.
Storage and Handling
Appropriate storage and management are perilous to maintaining the moisture resistance of PCB. A dry environment should be ensured that can prevent moisture absorption during storage.
- PCBs should be stored in controlled, low-humidity environments. It is important to store them properly to avoid moisture damage during the manufacturing of large circuit boards.
- Using dehumidifiers for storage as they can eliminate extra moisture from the air, protecting the PCBs from humidity-related issues.
- Use desiccant packs in packaging to absorb residual moisture.
- Handle PCBs with gloves to avoid direct contact and contamination.
- Avoid exposing PCBs to rapid temperature change.
- The moisture resistance of the PCB should be tested by subjecting the board to humidity and temperature cycles within the environment of electronics that can be employed to assess the performance of the PCB under extreme conditions of the environment.
Maintenance and Inspection
Regular maintenance and inspection help detect and address moisture-related issues early. Proactive measures ensure the long-term reliability of PCBs.
- Conduct regular visual and electrical inspections.
- Reapply protective coatings as needed. Incorporating mesh copper planes in a circuit board helps create stronger connections and reduces moisture movement between the layers.
- Clean PCBs to remove contaminants that attract moisture.
- Monitor environmental conditions to prevent moisture buildup. The procedure of making printed circuit boards (PCBs) is complex. As the number of internal layers in the PCB increases, the steps involved in manufacturing become more difficult, and there are more challenges to overcome and it is important to keep the manufacturing environment dry at all times.
How to Remove Moisture From PCBs?
If moisture has penetrated a PCB, it is crucial to remove it promptly to prevent damage. Several methods can be used to remove moisture from PCBs:
Drying Using Heat
Heating the PCB can help evaporate and remove moisture and can be accomplished by using a measured heat source, such as an oven or a reflow oven, at temperatures harmless for the PCB and its components. Care must be taken to avoid overheating and damaging the PCB.
- The PCBs are hygroscopic and absorb the air when they are stored and transported and the moisture leads to the delamination of the components of the PCB to avoid failure. The PCBs should be dried before processing for the removal of the moisture.
- Moreover, during the drying of the PCB, it is important to ensure that the top and bottom sides are not covered with plane copper.
Using Desiccants
Desiccants are used during PCB manufacturing to absorb moisture from the environment. PCBs are placed in an environment with desiccants, including silica gel packs, which can help absorb and eradicate moisture from the PCB. This technique is operative for slow, gradual drying.
Vacuum Drying
Vacuum drying involves placing the PCB in a vacuum chamber to mitigate the pressure and enable the evaporation of moisture. This technique efficiently eradicates moisture from deep within the PCB layer and is often used in amalgamation with heat.
- For the removal of moisture from PCB vacuum drying is effective as it decreases the risk of oxidation and corrosion
- It prevents damage to the sensitive components of the PCB by removing the moisture from small spaces and holes.
Alcohol Cleaning
To clean and remove moisture from PCBs, Isopropyl alcohol can be used. The alcohol dislocates moisture and evaporates swiftly, leaving the PCB dry. This technique is mainly useful for cleaning and drying restricted areas of the PCB.
Air Blowing
Compressed air is used to blow moisture off the PCB and can be an operative way to eliminate moisture from the surface of PCBs to avoid introducing additional contaminants, care should be taken to use clean, dry air.
Using Heat Guns
For the direct heat onto specific areas of the PCB heat guns can be used to evaporate moisture. This technique allows for targeted aeration but needs careful regulation of the heat to avoid destructive sensitive components.
Figure 6Moisture Detect Sensors
FAQs
Which coating protects PCB from moisture?
Conformal coatings include acrylic, silicone, polyurethane, and epoxy. Some are better suited to specific situations than others. Acrylic is simple to work with and change, silicone is extremely flexible and can resist high temperatures, polyurethane is exceptional at withstanding chemical degradation, and epoxy provides a strong barrier against moisture and mechanical stress.
Do PCBs absorb moisture?
Particularly if PCBDs are made of porous materials or if adequate coatings are not applied. This may happen during manufacturing, storage, or when the product is used in a humid environment, resulting in problems like corrosion, electrical shorting, and reduced functionality.
Final Words
This is pretty much clear that protecting PCBs from moisture is important for the reliability and longevity of electronic devices. Manufacturers and users can protect PCBs from moisture damage by understanding the elements that influence moisture penetration, using effective detection systems, and applying preventive solid and removal measures.
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