How to Handle Moisture Sensitivity in Circuits Assembly

Handle Moisture Sensitivity in Circuits Assembly

Circuits assembly involves many different components, including sensitive elements that can be damaged by moisture. For example, moisture in a capacitor can lead to dielectric absorption that reduces its performance. In a sensor, changes in humidity can alter the readings it is supposed to make. These issues can be very serious and cause the product to malfunction. There are a number of ways to prevent moisture from entering your PCBs, starting with proper handling. These techniques can also be used in the assembly and shipping processes to ensure that your circuit boards are protected against moisture damage.

Moisture Sensitive Devices (MSDs) are particularly susceptible to moisture absorption, which can shorten their lifespan and cause them to stop working properly. They are typically labelled with an MSD floor life and must be treated according to this specification. This includes using a desiccant to maintain ambient RH levels below their maximum tolerated value. In addition, it is necessary to follow a strict PCB production and assembly process that will prevent the entrance of moisture during manufacturing.

While the most common method of removing moisture from a circuits assembly is baking, this can have negative effects on its performance. Baking involves heating a board to high temperatures, which can cause the moisture molecules within the PCB to expand. This expansion can cause the components inside the package to erupt, destroying the lead-frame and wire-bonded connections. It may also lead to oxidation of the solder and corrosion of other metals on the PCB.

How to Handle Moisture Sensitivity in Circuits Assembly

Another way to prevent the ingress of moisture is to use a non-conductive epoxy on your PCBs. However, this method has its limitations and should only be used if your components are moisture-sensitive. This is because the epoxy can actually promote the uptake of moisture by allowing it to pass through the surface. Additionally, this type of coating does not provide true waterproofing and should only be used on parts that are not exposed to water.

The most effective technique for preventing the ingress of moisture into PCBs is to employ preventative maintenance practices throughout the assembly, handling, storage and shipping phases. This can include the use of a dehumidifier and the inclusion of an anti-corrosive epoxy that is moisture-resistant. Moreover, the manufacturer should use pick-and-place equipment to place components on the PCB and use no-clean flux when soldering these parts.

In addition to this, the manufacturer should consider implementing a dry box and using a desiccant in the packaging to protect it from moisture. The company should also test each batch of a product to ensure that it meets the required performance specifications. If any issues arise, the company should immediately notify its customers and rework or repair the products. In the long run, these precautions will help to ensure that each circuit board has a long lifespan and is reliable.

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