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Aldeno Technology Co., Ltd. is specially configured with 2 ANDA three-proof paint spraying production lines, including 1 three-proof paint spraying equipment, UV testing, baking, including fully automatic one-stop mode, professional and technical experienced engineers, adjusting the machine procedures to ensure that the board spraying uniformity and better results. Adopting the latest computer control programme, it is able to achieve three-axis linkage, and equipped with camera positioning tracking system, which is able to accurately control the spraying area. Three-proof paint coating machine, also known as three-proof paint coating machine, three-proof paint spraying machine, three-proof paint spraying machine, three-proof paint spraying machine, etc., is specialised in controlling fluids and covering the surface of PCB with a layer of three-proof paint, such as a layer of photo-resist on the surface of PCB by impregnation, spraying, or spin-coating. We will answer in this article what is the three-proof paint coating process, traditional coating and mechanical coating process comparison, three-proof paint common industry applications, the selection of three-proof paint precautions, three-proof paint coating operation specifications and process requirements, three-proof paint coating testing standards and so on.

PCBA three-proof paint coating machine is mainly used in the product process of glues, paints and other liquids to spray, paint and dripping to the precise location of each product, can be used to achieve the line, round or arc. Precise control of the spraying valve can ensure that 0.05mm thickness of the three defence coating effect is uniform and consistent, compared with the manual spraying, dipping, brushing and other ways of revolutionary improvement, greatly improving production efficiency and product quality.

PCBA circuit board three-proof paint coating process, mainly coating machine and traditional coating process, the comparison of the two processes are as follows:

(1) brush coating: bubbles, waves, brush hair removal;

(2) Brush coating: too slow, precision can not be controlled.

(3) The whole piece of immersion: too wasteful of paint, slow speed.

(4) Spray gun spraying: to jig protection, too much spraying

Coating machine coating

(1) The amount of spray paint, spray paint position and area is set accurately, and there is no need to wipe the board after spraying.

(2) Part of the plug-in components from the edge of the board spacing is large, can not be installed fixtures directly spray paint, saving the installation of the board staff.

3）No gas volatility, to ensure a clean working environment.

(4) All substrates without the use of fixtures to cover the carbon film, eliminating the possibility of collision.

5）Three-proof paint coating thickness is uniform, greatly improve the production efficiency and product quality, but also to avoid the waste of paint.

As electronic devices are more and more widely used in daily life, the quality and reliability of the product is more and more concerned by consumers, and the use of three-proof paint common lamination can effectively protect the circuit from damage, thereby improving product quality and reducing the cost of expensive warranty failures.

Three-proof paint is also known as PCB electronic circuit board protection oil, coating oil, moisture-proof paint, three-proof paint, waterproof adhesive, insulating paint, corrosion-resistant paint, anti-salt spray paint, dust-proof paint, protective paint, coating paint, three-proof adhesive, etc., is a kind of protection of electronic circuit boards of the adhesive, is mainly used for the protection of the circuit boards and their related equipment from the erosion of the bad environment, so as to improve and prolong their service life, in order to ensure the use of the security and Reliability.

In real conditions, such as chemical environments (combustion, coolants, etc.), vibration, high dust, salt spray, humidity and high temperatures, etc., circuit boards may corrode, soften, deform, mould, etc., which can lead to failure of the circuit board circuit. Three-proof paint coated on the exterior of the circuit board, cured to form a transparent protective film, with superior insulation, moisture-proof, anti-leakage, anti-vibration, dust-proof, anti-corrosion, anti-aging, corona resistance, resistance to high and low temperatures and other properties.

① Three-proof paint can protect electronic equipment from water, moisture, external chemicals and special use of the environment, to ensure its continued stability, its application is very broad, such as LED display, LED guardrail tube, solar energy instrumentation, power supply, inverters, consumer electronics, anti-theft and fire alarm devices.

② water and detergent is a washing machine, dishwasher, bathroom products, outdoor electronic LED screen and other electronic products in the damage to the circuit is an important factor, the need to apply three anti-painting on their electronic circuits to form an effective protective layer against their erosion.

③ computers, induction cookers, etc. are often caused by harmful substances in the office or at home to cause failures, three-proof paint for its use in the process of harmful substances prone to affect the work and the use of the quality of the problem provides a good solution.

The quality requirements of each component inside the car are very high, and three-proof paint is needed to protect the circuits from the hazards of petrol evaporates, salt spray, brake fluid and other substances. The application of electronic systems in automobiles is growing, and the three-proof process for automotive electronics is developing rapidly. Involved in the three-proof with components are mainly electronic controllers, automotive air conditioning, instrument panels, sensors, car navigation, etc..

Due to the special characteristics of the use of the environment, aviation, aerospace environment on electronic equipment requirements are strict, especially in the rapid pressurisation, depressurisation conditions, but still to maintain good circuit performance, three-proof paint pressure stability is therefore widely used. Such as satellite systems, military control systems, flight line control systems.

Whether it is fresh fresh water or salty seawater, will cause harm to the electrical circuits of marine equipment. The use of three-proof paint can maximise the protection of equipment on the water surface and even submerged underwater. Such as navigation systems, radar control systems, etc.

Triple-proof paint protects medical electronic equipment from external chemicals and special usage environments, ensuring its continued stability.

1, The working environment: people for the physical resistance of electronic equipment and chemical resistance to different requirements, such as pressure resistance, shock resistance and waterproof, acid and alkali corrosion resistance, etc., therefore, must be for different working environments, the choice of different characteristics of the three-proof paint.

2, Electrical performance requirements: three-proof paint should have a high insulation strength and breakdown voltage; three-proof paint minimum insulation strength requirements can be printed from the spacing of the line as well as the potential difference between adjacent printed lines to determine.

3, The layout of the circuit board: the design of the circuit board should take into account the placement of components without lamination, including connectors, IC sockets, tunable potentiometers and test points, should be placed on the edge of one side of the circuit board, in order to achieve the simplest coating process and the lowest coating costs.

4, The use of methods: in the use of three-proof paint before, should be thoroughly on the surface of the circuit board with corrosive residues cleaned to ensure that the three-proof paint is well adhered to the surface of the circuit board.

5, Secondary processing and maintenance: As most of the circuit board there is the possibility of rework, recycling, so the film needs to be easy to remove and processing requirements. At present, most of the three-proof paint can achieve safe soldering operations, there are a number of film layers can be removed with standard organic solvents.

Triple-proof paints (common overlays) are chemically classified into three main categories: acrylates, silicones and polyurethanes. In terms of curing methods, there are solvent curing, room temperature curing, heat curing and UV curing to choose from.

1、Solvent-containing acrylic resin three-proof paint: surface drying, fast curing time, better three-proof, cheap, transparent colour, flexible texture, easy to repair features.

2, solvent-free acrylic resin three-proof paint: UV curing, can be in a few seconds to more than a dozen seconds table drying, transparent colour, hard texture, anti-chemical corrosion and abrasion resistance is also very good.

3, polyurethane three-proof paint: brittle texture, excellent solvent resistance; not only superior moisture-proof performance, but also in the low-temperature environment, stable performance.

4、Silicone three-proof paint: soft elastic coating material, can release pressure very well, high temperature resistance of 200 degrees, easy to repair.

5、Fluorescent three-proof paint: after coated with fluorescent three-proof paint, the violet light irradiation coating surface shows blue colour, which is clear and easy to detect whether the three-proof paint is coated in place.

- Traditional manual painting will have poor consistency, quality accidents (such as three-proof paint penetration into the LCD screen, socket, etc.), uneven thickness, three-proof paint mixed with impurities. The use of professional three-proof paint coating production line can effectively avoid these defects, with fast speed, high reliability, one-stop baking and curing and other advantages.

- Large size PCBA boards, such as 550mm*470mm, etc.

- Provide matching PCBA board carrier to ensure the uniformity of edge coating.

- Supports the coating of dense PCBA boards with a lot of tall components.

- Sector spraying and dot-pin spraying can cover all kinds of component surfaces.

- According to the actual needs of customers, you can selectively avoid certain components, such as connectors, antennas, Wifi modules, heat sinks and so on.

- Support double-sided coating and baking

- Full-automatic equipment, the average spraying time of each board is within 0.5~3 minutes.

1、Three-proof paint exceeds the shelf life, prohibited from use.

2、Storage containers should be kept airtight after opening.

3, the use of the remaining three-proof paint is prohibited to pour back into the original storage container, to be separated from the airtight storage.

4, long time (more than 12 hours) did not open the workroom or storage room, should be ventilated for 15 minutes before entering.

5、Inadvertent splashing into the glasses should immediately turn over the upper and lower eyelids, rinse clean with flowing water or saline, and then seek medical treatment.

6、If you feel uncomfortable when brushing, you should leave the work site to the fresh air quickly, and give oxygen when you have difficulty in breathing, and then seek medical treatment.

According to the requirements of IPC-A-610E (Electronic Assembly Inspection Standard) and factory regulations, there are mainly in the following aspects:

Paint preparation: PCB to be sprayed for appearance check, if the board surface has obvious handprints, stains and other poor appearance, it must be cleaned with a cleaning agent and wait until the cleaning agent thoroughly evaporated before entering the next process.

What are the operational requirements for coating PCBA three-proof paint?

1、Three-proof work should be carried out in a separate room, but not completely closed, there must be good ventilation facilities.

2, the operation room prohibits smoking, eating, drinking, do not quote alcoholic beverages before work.

3, the operation should wear a good mask or gas mask, rubber gloves, chemical protective glasses and other protective equipment, so as not to injure the body, which also depends on the choice of the three-proof paint products, if it is a stupid-containing products should pay close attention to the protection and fire prevention, and if it is the TIS-NM environmental protection of three-proof paint products, it is a lot of security, and will not have the risk of combustion.

4、After the work is finished, we should clean the used utensils in time, organise, sassafras test tools and equipment, and containers with three-proof paint cover tightly.

5, the workplace should be clean and dust-free, no dust flying, and prohibit the entry of unrelated personnel.

6, tools and equipment should be fully grounded, and do a good job of electrostatic protection measures.

7, do not overlap the PCBA placed during operation; PCB board to be placed horizontally.

8, each batch of raw materials before use, should do a small sample curing test (3-5PCS).

9, clean and bake the board, remove moisture and water. The surface of the object to be coated with dust, moisture and oil must be removed in order to give full play to its protective effect. Thorough cleaning ensures that corrosive residues are completely removed and that the three-proof paint adheres well to the surface of the circuit board. Baking conditions: 60 ° C, 10-20 minutes, in the oven after the removal of the heat coating better;

10、The board should be placed as flat as possible when brushing, and there should be no dripping dew after brushing, and the brushing should be flat, and there should be no bare part, between 0.1-0.3mm is suitable.

11, before brushing and spraying, make sure the diluted product is fully stirred and left for 2 hours before brushing or spraying. Use a high quality natural fibre brush to gently brush and dip coat at room temperature. If using machinery, the viscosity of the paint should be measured (with a viscosity agent or flow cup), and the viscosity can be adjusted using a thinner.

12. PCB assemblies should be immersed vertically in the paint dregs. Connectors should not be immersed, unless carefully covered, the circuit board should be immersed for 1 minute until the bubbles disappear, and then slowly take out. A uniform film layer will form on the surface of the circuit board. Most of the paint residue should be allowed to flow from the circuit board back into the dipping machine. the TFCF has different coating requirements. The circuit board or components should not be immersed too fast to avoid excessive air bubbles.

13, dip coating after the end of re-use, if the surface has a crust phenomenon, remove the skin, can continue to use.

14, brush coated flat on the bracket, ready to cure, the need to use heat to accelerate the curing of the coating. If the surface of the coating is not flat or contains bubbles, in the high-temperature oven into the curing should be placed at room temperature for more time in order to let the solvent flash out.

1, brush the three anti-paint protection shall be in the PCBA assembly before the test, inspection and thoroughly clean.

2, the use of the brush to keep clean, prohibit the use of other operations; brush paint should be careful not to drip to the part of the paint does not need to be painted; use the brush after the use of thinners and other cleaning.

3、The coating layer should be transparent and evenly cover the PCB board and components with uniform colour and consistency.

4, the process steps are: painting A surface → surface drying → painting B surface → room temperature curing

5、Spray thickness: spray thickness of 0.1mm-0.3mm (dry film thickness is generally 30-100UM)

6, all coating operations should not be less than 16 ℃ and relative humidity of less than 75% of the conditions. PCB as a composite material will absorb moisture, such as not going to the moisture, three-proof paint can not fully play a protective role, pre-drying, vacuum drying can remove most of the moisture.

PCBA which components can not be coated with three-proof paint?

1, high power with heat sink or heat sink components, power resistors, power diodes, cement resistors.

2、Dial switches, adjustable resistors, buzzers, battery holders, fuse holders (tubes), IC holders, flick switches.

3, All types of sockets, row of pins, terminals and DB header.

4, Plug-in or paste type light-emitting diodes, digital tubes.

5、Other parts and devices which are not allowed to use insulating varnish as specified in the drawings.

6, PCBA board screw holes can not be painted three-proof paint.

Can not be coated areas: ①, the need for electrical connection of the region, such as gold pads, gold fingers, metal through-hole, test holes; ②, the battery and the battery mount; ③, the connector; ④, the fuse and the shell; ⑤, the heat dissipation device; ⑥, the jumper; ⑦, the lens of the optical device; ⑧, potentiometers; ⑨, sensors; ⑩, no sealing of the switch;

Areas that must be coated: all solder joints, pins, and conductor parts of components.

Coating inspection AOI equipment multiple LED-type scanners can produce parallax-free and distortion-free images by installing special lenses in the scanner lens system.

Inspection features: ①, large detection range: 650 * 600mm; ②, fast detection speed, high resolution, high precision; ③, independent track, autonomous control (can be straight through can be reversed); ④, support for communication, compatible with the NG Buffer, reduce staffing;

Combined with a variety of glue detection tasks overflow or drawing, cracking, shrinkage of glue, orange peel-like surface defects, bubbles, pinholes, foam, glue thickness, waves, scattering, gluing area.

All self-colouring UV glues with phosphors can be inspected.

Appearance inspection is generally in accordance with the customer‘s project product parameters and IPC-CC-830B requirements to detect, through the fluorescent lamp irradiation, the details of the surface of the three-proof paint is easy to be detected, most customers are now using manual inspection, of course, can also be imported into the automatic optical inspection system AOI, which can greatly improve the efficiency. The above picture is the effect of manual UV fluorescent lamp irradiation.

PCB three-proof paint coating thickness standard requirements: most of the circuit board products coated with the normal thickness of 25 to 127 microns, some of the products are coated with lower thickness.

How to use the tool to measure

Circuit boards must be coated with the thinnest possible coating material to provide maximum protection and to minimise heat retention, additional weight gain and a variety of other problems. There are three primary methods to measure the thickness of a conformal coating.

Wet Film Thickness Gauges - Wet film thickness can be measured directly using a suitable gauge. These gauges contain a series of notches with each tooth having a known calibrated length. A thin film measurement is taken by placing the gauge directly on the wet film and this measurement is then multiplied by the percentage solids of the coating to calculate an approximate dry coating thickness.

Micrometer - Micrometer thickness measurements are taken at several locations on the board before and after the coating occurs. The thickness of the cured coating is subtracted from the thickness when it was uncoated and divided by 2 to obtain the thickness of one side of the board. The standard deviation of the measurement is then calculated to determine the uniformity of the coating. Micrometer measurements are best made with harder coatings that do not deform under pressure.

Ultrasonic Thickness Gauge - This gauge uses ultrasonic waves to measure coating thickness. It has advantages over eddy current probes because it does not require a metal backing plate. The thickness depends on the amount of time it takes for the sound to travel from the transducer, through the coating, and reflect back off the surface of the PCB. This method is relatively safe and does not damage the PCB.

Three-proof paint testing standards, there is no perfect unified standards, enterprises generally refer to the national standards (GB) and IPC part of the actual situation, and then combined with their own, self-defined in line with their own corporate standards, according to a number of large-scale listed group companies to see the use of the situation, and often self-defined standard requirements, are far more than the national standards and IPC standards. In the field of electronic industry, each enterprise produces different products, the quality of three-proof paint, testing standards are not the same requirements. We believe that the three-proof paint coating suitable for customer product needs, can create value for customers is a good test standard, the following is roughly categorised with 26 test items:

1: adhesion (refer to GB/T9286-1998 standard: scratch test method)

2: salt spray test (reference GB / T 1771-2007 standard: to verify the safety performance of the product. Standard 72h, enterprises need suppliers to cooperate with the limit of experiments up to 1000h)

3: water absorption (reference GB / T 1738-1979 standard: verification of product protection, safety performance)

4: insulation resistance under humid environment (refer to IPC-TM-650 2.6.3.4A standard: verify the insulation safety of the product)

5: Mould resistance (refer to IPC-TM-650 2.6.1 standard: 28 days mould test)

6: weatherability / thermal shock test (reference IPC-TM-650 2.6.7.1A standard: IPC standard 100 cycles, enterprises need suppliers to cooperate with the limit of experiments up to 600 cycles)

7: Acid and alkali resistance test (refer to GB1763-1986 standard: no abnormality of paint film)

8: Breakdown strength (refer to GB1981.2-2003 standard: verify the insulation performance of the product)

9: Corrosion (refer to IPC-TM-650 2.6.15 standard: no corrosion of the test sample)

10: Odour requirements (company‘s own standards: small odour, no irritating unpleasant odour)

11: Toxicity requirements (refer to JIS K0123-2006 GC-MS standard: not only to comply with RoHS, REACH directive, but also require the absence of benzene, toluene, xylene, ethylbenzene, acetone and other toxic substances)

12: Flexibility of paint film (refer to IPC-TM-650 2.4.5.1 standard: the paint film needs to be bent 180 degrees without cracks)

13: resistance to vulcanisation test (enterprise self-defined test standards: to verify the long-term protective performance of the product, silicone products due to its molecular structure of its own reasons, the molecular gap is large, the test can not be passed. Silicone products have good heat dissipation performance, but the air moisture, hydrogen sulfide and other gases for a long time by the molecular gap in the uninterrupted erosion, resulting in the gradual vulcanisation of the bottom of the plate corrosion, some large companies have gradually recognised the defects of the product, for the service life of the product requirements have been prohibited.)

14: heat resistance (enterprise self-defined standards: cured paint film placed in the temperature of 65 ± 5 ℃, humidity of 90 ~ 95 of the constant temperature box 168h, the paint film should be no abnormality. Verify the weather resistance of the product)

15: Flame retardant (need fire retardant certification, flame retardant grade 94V-0: verify the flame retardant properties of the product)

16: oil resistance (refer to GB1739-1979 standard: verify the environmental adaptation and safety performance of the product)

17: Halogen content (refer to IPC-TM-650 2.3.35 standard: special environmental requirements)

18: Acid value (refer to GB/T 1981.2-2009 standard: verify the safety performance of the product)

19: Viscosity (refer to GB/T 1981.2-2009 standard: to verify the ease of use of the product)

20: Stability (refer to GB/T 1981.2-2009 standard: to verify the durability of the use of the product)

21: Drying time of paint film (refer to GB/T 1981.2-2009 standard: verify the efficiency of the use of the product)

22: Volume resistivity (refer to GB/T 1981.2-2009 standard: verify the safety performance of products)

23: Electrical strength (reference GB/T 1981.2-2009 standard: verify the safety performance of the product)

24: Dielectric withstand pressure (refer to GB/T 1981.2-2009 standard: verify the safety performance of the product)

25: Density (refer to ISO 2811.4-2011 standard: verify the consistency of product supply)

26: Infrared spectroscopic measurements (refer to standard GB/T 6040-2002: Verification of consistency of product delivery)