Comparative analysis of three methods of circuit board waterproofing (structural waterproofing method, potting waterproofing method, three anti-painting)
Where is the waterproof path of the board? For many engineers, circuit board waterproofing has always been a headache. In order not to delay the construction period, in order to pass the inspection, how many days and nights struggle in the first line, research various molds, full of brain injection, sealing, exhaust , a variety of pads, diversion, heat dissipation, deformation, mold opening costs. How to make the product waterproofing process easier, we need to think about improvement and try it out. What are the most common technologies on the market to solve this "headache problem"?
Structural waterproofing
Structural waterproofing is the most traditional mode of waterproofing of electronic products. It should also be the first method that most engineers think of. The main idea is hydrophobic, diversion, effective isolation of external packaging and internal electrical parts, mold design of products and various seals. Blocking is the main point, of course, the more complex the mold is not cheap.
Compared with a switching power supply, the mold is opened to make a plastic case, the circuit board is put into the box and the plastic case is sealed, and the water is sealed from the outside to achieve the purpose of waterproofing.
The seams of the shell are concave and one is convex, and a waterproof rubber ring is placed in the middle and the locking has achieved the sealing effect. Some also directly seal the shell after hot-sealing, but it is not easy to repair.
The cost of waterproofing is also relatively high. For some small companies, if the order quantity is small, it is not worthwhile to open the mold.
In theory, a waterproof shell should be made similar to a submarine.
Unfortunately, even if there are many changes in the structure, it is still unable to better prevent the intrusion of moisture. The circuit board is used in an environment with heavy water vapor. The appearance of the appearance itself is also subject to the risk of deformation. The gap will also be deformed, or the artificial non-human damage of the appearance will always exist and become a potential concern.
Advantages: good waterproof effect
Disadvantages: The process is difficult to guarantee, and the structure has the risk of deformation.
Potting waterproofing method
Potting method waterproofing It is common to use epoxy resin potting glue, which is used for potting of electronic product modules. It can wrap the whole pcb board to protect it from water, moisture, salt spray, mold and shock. Epoxy resin is a saturated resin. Epoxy resin potting compound produced on the substrate has high bulk strength, strong adhesion, good weather resistance, low shrinkage, high dielectric strength, and no It has the characteristics of poison and environmental protection, and it can stabilize the mechanical and electrical properties between -45-120 °C after potting. It can protect the board in all directions and greatly improve the service life of the board. But at the same time there are some more deadly problems, such as the heat dissipation of the pcb board will be very affected, the most troublesome is that the product has almost no possibility of repair, or the cost of repair is too high.
Because the potting glue has good thermal conductivity, it can help the heat dissipation after the potting of the power board, but the EMI will become larger after the board is potted.
Circuit board resin potting glue waterproof
Advantages: waterproof effect is very good
Disadvantages: high cost, too difficult to repair
Surface coating waterproofing
The three anti-paints are also called circuit board protection oil, coated oil, waterproof glue, insulating paint, moisture-proof paint. The three anti-paint products are generally thick, basically the coating thickness will reach 50 microns, the heat dissipation is not good, and the viscosity is high. The output of one kilogram is relatively low, the drying is slow, and it takes even one or two hours to dry. The three anti-paint is coated on the electronic PCB board to cure the moisture, corrosion and salt spray. However, this film can only protect against moisture and a small amount of water. If the electronic product is completely immersed in water, it will be ineffective. Because of the technical effect of the three anti-paint, it is not resistant to falling, not resistant to vibration, and is easily peeled off by external force. The protective effect of the pcb board is very limited, and it is difficult to see whether it is evenly coated by direct observation by the naked eye. At present, many three anti-paints still use volatile solvents, which are very harmful to the human body and the environment. For some manufacturers that want to export to Europe and the United States, the environmental protection can not meet the standard.
The potting compound has more protective effects on the circuit board than the three anti-paint. If you only need to play a basic protective role, you can use three anti-paint protection.
Circuit board three anti-paint
Advantages: low cost
Disadvantages: poor waterproofing, not environmentally friendly
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