Most people who have worked on PCBA production lines or after-sales services have been "tortured" by the three proof paint.

After the coating is cured, if you want to repair it, you can either scrape it with a blade or soak it in a solvent. If you are not careful, the solder pads will be lifted and the components will be scrapped. Especially now that boards are becoming denser and components are becoming smaller, the contradiction of "strong protection but unable to repair" is becoming increasingly prominent.

That's also why in recent yearsNano coating of inorganic silicon systemIt has begun to attract attention from high-end production lines - it is not simply a "replacement for three proof paint", but a molecular level reconciliation of the originally opposing needs of "protection" and "repairability".

We will focus on a specific product today——Electronic nano waterproof coating (inorganic silicon system)——For example, let's take the idea of dismantling this type of new material

01-Why is it "inorganic silicon" instead of "organic silicon""

Traditional three proof paints are mostly organic systems such as acrylic, polyurethane, and silicone, which have the advantages of soft film formation and mature application, but the disadvantages are:

• After long-term resistance to moisture and heat, it is prone to yellowing and powdering

• Difficult to remove after curing, repair damaged board

• The upper limit of temperature resistance of organic resin itself is generally (mostly within 150 ℃)

The inorganic silicon system is taking a different path——Hydrophobic modified nano inorganic siliconAs a substrate, a transparent and dense silicon crystal film is formed at room temperature through small molecule cross-linking, with a thickness of only 600-800 nm, which is equivalent to "piercing a second layer of skin through the circuit board".

1MaterialInorganic silicon vs organic resin → Higher upper limit of aging resistance and yellowing resistance

2film thickness600-800 nm vs traditional three proof paint 30-100 μ m → two orders of magnitude difference, does not affect heat dissipation, does not block sensors

3reworkSpecial solvent erasable vs traditional three proof paint difficult to remove → This is the most important point on the production line

02-A few hard parameters, let's first see what TDS says

What is the interesting aspect of this set of data?

Dielectric strength ≥ 80 kV/mm+volume resistance level 10 ¹⁵——Putting these two together indicates that it is not only "waterproof", but also an "insulation barrier". For scenarios such as high voltage, high impedance, and precision analog circuits, it is more critical for the insulation layer not to be penetrated by water vapor than simply hydrophobic.

1000h humid heat+200h salt spray - this is the entry threshold for industrial/automotive scenarios. By this scale, it can basically cover the complex working conditions of "moisture+corrosion+temperature change" such as in vehicle central control, charging pile control board, and industrial sensors.

03-Why has' erasable 'become a new selling point

1. Defective production line repair → coating cannot be removed → whole board scrapped or repair time doubled

2. After sales replacement → Coating cannot be partially repaired → High cost of dismantling and reinstalling

3. Chip refurbishment/upgrade → non removable coating → direct disposal of board

Electronic nano waterproof coatingThe idea is that the coating can be completely dissolved and wiped off by a dedicated environmentally friendly solvent after curing, without damaging the substrate or components. This means:

1. Troubleshooting can partially remove the coating → repair before reapplying

2. Chips can be disassembled and refurbished → Board reuse

3. Production line defects can be reworked → there is no need to scrap the entire board

There is a small trend in the industry here: In the past three years, IEEE/SMTA has published several papers on "reworkable conforming coating" to discuss this direction - the ROI of peelable/soluble electronic coatings in high-end production lines has been verified, especially for the rework of close spaced devices such as BGA and CSP [ 2 ] .

04-Construction: Compatibility with existing production lines is a prerequisite for implementation

No matter how good the parameters are, it's useless to connect the production line. The section on electronic nano waterproof coating is written relatively restrained:

1Single component, no blending required——A: B doesn't need to be weighed, it can be used immediately after opening the lid

2Process compatibilityDip coating, spray coating, and wiping are all acceptable, and can be connected to automated lines

3solidify4 hours of dry operation at room temperature, can be heated to increase speed, no need for an oven

4PreprocessingEthanol cleaning of the substrate is sufficient, without the need for complex masking

Applicable scenarios: Four major mainstream high-value scenarios

1Consumer Electronics:Mobile phone motherboard, TWS earphones, smartwatch - the core requirement is waterproof and moisture-proof, while not affecting heat dissipation and signal transmission. The ultra-thin film thickness of 600-800nm has significant advantages in this regard.

2Industrial control:Industrial control PCBs, high-precision sensors, communication modules - These devices operate in humid, dusty, and condensed environments year-round, requiring high weather resistance and salt spray resistance of coatings. The test data of 1000h humid heat+200h salt spray can basically meet the entry threshold of most industrial scenarios.

3Automotive Electronics:The characteristics of the car interior environment include alternating high and low temperatures (-50 ℃ to 200 ℃), vibration, and possible condensation, including the onboard central control board, headlight circuit, and charging station control board. The stability of inorganic silicon systems under such composite conditions is one of the main reasons for its attention.

4Smart Home:Smart door locks, bathroom appliances, security cameras - the humid steam in kitchen and bathroom areas, and the day night temperature difference of outdoor equipment all pose long-term requirements for the protection of circuit boards. The erasable repair feature is particularly useful in the after-sales process of such products.

06-A little summary

Looking back, inorganic silicon nanocoating is not an addition to the "three proof paint", but a re evaluation of three things:

• thin(600-800nm) → Does not interfere with heat dissipation and signals, and does not affect assembly accuracy

• hard(Inorganic silicon skeleton) → Resistant to aging and temperature up to 200 ℃, able to withstand hot, humid and salt spray

• reversible(Erasable Repair) → The full lifecycle cost has been reduced, benefiting both the production line and after-sales service

Only when these three things are established simultaneously can we truly touch the edge of 'next-generation electronic protection'. If you happen to have boards evaluating protection solutions or have been troubled by repair issues with three proof paint, you may want to include inorganic silicon nano coatings in the comparison list.

References

【1】 Progress in the application of inorganic silicon nanocoating in electronic packaging (review category, can be searched on CNKI for recent literature on the positioning of "inorganic silicon nanocoating electronic packaging")

【2】 The direction of peelable/repairable electronic coatings can refer to relevant SMTA/IEEE conference papers