PCB Nano Conformal Coating Selection: TUW-2704 & TUW-1700 vs. Traditional Conformal Coating
2026-10-21
A new-energy vehicle control board in the engine bay has to withstand heat, vibration, moisture and salt spray at the same time. The conventional approach is to spray on a conformal coating, polyurethane or acrylic, tens of micrometers thick, wrapping the whole PCB.
But as automotive and consumer electronics move toward ever higher density, the problems of conformal coatings are showing: device spacing has shrunk below 0.5 mm, so the coating cannot flow into the gaps; the area under a BGA cannot be covered; rework means scraping off a thick layer of coating and often damages the pads; and a thick coating also harms heat dissipation.
That is how fluoropolymer ultra-thin coatings came into view. TUW-2704 and TUW-1700 are products of this kind: hydrofluoroether serves as the solvent, the film forms as the solvent evaporates, no additional curing is needed, local rework is possible with a cleaning agent, and quality inspection is easy under blue or UV light. This article compares them with conventional conformal coatings and sets out which scenario calls for which product.
1. How Fluoropolymer Coatings Work
TUW-2704 and TUW-1700 are both coating solutions made by dissolving fluoropolymer in a hydrofluoroether solvent. They are applied to the PCB by spraying, immersion or selective coating, and once the solvent evaporates quickly the polymer forms an extremely thin transparent film on the surface.
The defining property of fluoropolymers is very low surface energy: neither water nor oil can settle on them. Thin as it is, at a few micrometers or even one micrometer, the film is enough to form a barrier against moisture, salt spray and oil contamination.
The biggest difference from conventional conformal coatings lies in how the film forms. Conformal coatings need heat or UV curing and involve a long waiting interval before curing, whereas TUW-2704 and TUW-1700 need no additional curing: film formation completes as the solvent evaporates quickly, so they fit into existing lines without disruption and cut the time of the protection step substantially. The solvent and the polymer are also very safe, do not deplete the ozone layer, and comply with RoHS.
2. Parameter Comparison of the Two Products
TUW-2704 and TUW-1700 both belong to the hydrofluoroether-based fluoropolymer coating family. Their core parameters are compared below:
Table 1 Core parameter comparison: TUW-2704 and TUW-1700
|
Parameter
|
TUW-2704
|
TUW-1700
|
|
Product positioning
|
Electronic coating agent (nano coating)
|
Electronic coating agent (nano coating)
|
|
Solvent system
|
Hydrofluoroether (HFE)
|
Hydrofluoroether (HFE)
|
|
Solid content
|
4 wt% fluoropolymer
|
2 wt% fluoropolymer
|
|
Coating thickness
|
0.1–4 μm
|
0.1–1.0 μm
|
|
Appearance
|
Transparent liquid
|
Transparent liquid
|
|
Density
|
1.52 g/mL
|
1.52 g/mL
|
|
Flash point
|
None
|
None
|
|
Dry film heat resistance
|
175°C / 24 hours
|
175°C / 24 hours
|
|
Curing method
|
No additional curing required
|
No additional curing required
|
|
Reworkability
|
Easy rework with cleaning agent
|
Easy rework with cleaning agent
|
|
Quality inspection
|
Clearly visible under blue/UV light
|
Clearly visible under blue/UV light
|
|
Environmental compliance
|
ODP=0, RoHS compliant
|
ODP=0, RoHS compliant
|
Put simply, TUW-2704 gives a thicker coating and stronger protection; TUW-1700 is thinner, more transparent, and has less effect on appearance and dimensions.
3. Fundamental Differences from Conventional Conformal Coatings
The differences between ultra-thin coatings and conformal coatings centre on thickness, coverage capability and rework method:
Table 2 Ultra-thin coating versus conventional conformal coating
|
Comparison dimension
|
Conventional conformal coating
|
TUW ultra-thin coating
|
|
Coating thickness
|
Tens of micrometers
|
0.1–4 μm
|
|
Gap coverage
|
Hard to penetrate gaps below 0.5 mm
|
Low surface tension, penetrates naturally
|
|
Under BGA
|
Cannot be covered
|
Can be covered
|
|
Curing method
|
Requires heat or UV curing
|
Film forms as the solvent evaporates, no curing
|
|
Rework
|
Grinding and stripping, pads easily damaged
|
Local removal with a dedicated cleaning agent
|
|
Appearance
|
Visible coating
|
Virtually invisible
|
|
Heat dissipation
|
Thick coating hinders heat dissipation
|
Extremely thin, minimal thermal effect
|
|
Quality inspection
|
Visual check or thickness gauge
|
Clearly visible under blue/UV light
|
One point should be stated objectively: ultra-thin coatings are not meant to replace conformal coatings but to complement them. In scenarios with heavy salt spray, prolonged water immersion or aggressive chemical corrosion, conformal coatings remain the main option. In the following scenarios, however, ultra-thin coatings offer distinct advantages.
4. TUW-2704: Stronger Protection, Easy Rework
TUW-2704 has a solid content of 4% and a coating thickness of up to 4 μm, making it the stronger of the two in protection, with dry film heat resistance of 175°C/24 hours. It suits boards with high heat output and demanding protection requirements. Beyond thickness, it offers several very practical advantages:
4.1 Five Engineering Advantages
-
Easy rework: local removal with a dedicated cleaning agent is enough; there is no need to grind the whole board as with conventional conformal coatings, and pads are not easily damaged
-
Intuitive inspection: the coating is clearly visible under blue or UV light, so uniformity and missed areas are obvious at a glance, which supports in-process quality control
-
No curing: the film forms as the solvent evaporates, removing the curing oven step and shortening the production cycle
-
Thermal and electrical stability: good thermal stability and insulation performance, high insulation and strong weather resistance for more reliable long-term operation
-
Flexible and superhydrophobic: the coating bends with the board and suits flexible FPC boards, and water and oil cannot spread on the surface
4.2 Typical Applications
In concrete applications, TUW-2704 suits:
-
New-energy vehicle control units (VCU, BMS, OBC mainboards): high protection requirements, but high board device density makes conventional coating difficult to apply
-
Charging pile control boards: installed outdoors, facing moisture and condensation from temperature swings
-
Energy storage BMS boards: running long-term inside cabinets, requiring moisture protection but not suited to thick coating
-
5G base station RF modules: small device spacing, requiring uniform coating
5. TUW-1700: Invisible Protection and an Oil-Blocking Barrier
TUW-1700 has a solid content of only 2% and a dry film thickness of 0.1–1 μm, making it genuinely invisible protection: almost imperceptible to the eye, with minimal effect on appearance, tolerances and heat dissipation. Alongside the easy rework, blue/UV visibility, no curing, and high insulation and weather resistance it shares with TUW-2704, it has one unique value: control of oil diffusion.
5.1 Oil-Blocking Barrier Function
Lubricants and flux residues inside a phone can creep along the PCB surface into other areas and cause short circuits. With 1700 applied, oil cannot spread on the fluoropolymer film, which amounts to drawing an oil-blocking barrier on the PCB.
5.2 Typical Applications
In concrete applications, TUW-1700 suits:
-
Smartphone mainboards and camera modules: high appearance requirements, no visible coating allowed
-
Wearable devices such as watches and earphones: extremely limited internal space, thick coatings not permitted
-
Precision sensors: sensitive to tolerances, coating thickness must stay within 1 μm
-
Around optical lenses: optical performance must not be affected
6. Selection Recommendations
How to choose? A simple decision tree:
If the product works in heavy salt spray, high humidity or long-term water immersion, such as offshore equipment or outdoor cabinets, keep using conventional conformal coatings; ultra-thin coatings are not enough.
If the product is a high-density PCB with small device spacing and frequent rework, such as automotive electronics or consumer electronics, evaluate TUW-2704 or TUW-1700 first.
If appearance requirements are extremely high and the coating must not be visible, as inside a phone, choose TUW-1700; if a certain coating thickness is needed but conventional coating is difficult to apply, choose TUW-2704.
7. Points for Use
-
The PCB must be cleaned thoroughly before coating, otherwise oil contamination will affect coating adhesion
-
The application method (spraying, immersion or selective coating) must be determined by product shape and batch size
-
Protection performance should be verified with a damp heat test (85°C/85%RH, 1000 hours) and a salt spray test
-
Coating thickness must be measured with a film thickness gauge, not estimated from solid content alone
-
The dry film heat resistance limit is 175°C/24 hours; for long-term high-temperature operation, evaluate against the actual operating temperature
Shenzhen Huayi Brothers specializes in electronic fluorinated liquids and fluorine-based functional fluids, and provides product documentation, sample testing and discussion of application solutions.
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