The application of notebook PC plastic coating

Laptop plastic parts as well as the development and application of coatings and coating

   On April 1, 1974, Intel unveiled its individual user oriented microprocessor after 8080, the personal computer gradually began to enter in the office and home. With the unprecedented development of Internet technology and multimedia technology with a large number of applications, nowadays, computer has been completely change our life. Computer from a small size lab machine to desktop LCD computer now, laptops and the most popular, lightweight laptops, color also is multifarious, especially laptop computers and laptops, like clothing or a car, every year there are different popular colour pattern to attract the attention of consumers.

  Laptop (small laptops) shell material for plastic, metal, two main types:

  (1) plastic categories: low cost, easy to manufacture, mainly by the molding mould injection molding. Used in laptop computers and laptops plastic ABS, ABS + PC, PC, PP, NYLON, composite materials, etc.
  (2) metals: mainly casting of magnesium alloy, aluminum alloy, the casting of magnesium aluminum alloy, titanium alloy and a small number of components used stainless steel.

   Plastic substrate and spraying coating is still the mainstream. This paper mainly introduces the portable computer plastic coating and its coating.

  1 plastic material properties
  Common plastic material properties:
  ABS, acrylic, butadiene and styrene polymerization. General ABS resin composition: A is 25% ~ 30%, and B is 25% ~ 30%, S is 50% ~ 40%, the proportion of 1.07 ~ 1.15. Its characteristics are as follows:

    Opaque, uneven; Not high heat resistance, good processability, Meet the thermal deformation temperature of 60 ~ 120 ℃, the general has long been at above 90 ℃ ambient temperature deformation; Have stronger physical properties; Weather resistance is poor, not resistant to uv rays, reduce impact long exposure in the sun; Solvent will melt, but better resistant to acid and alcohol resistance; Combustion would produce peculiar smell; Good electrical properties; High surface gloss. ABS surface can spray paint, printing, vacuum coating and painting, the most suitable for 3 c products.

  PP (polypropylene), specific gravity of 0.9 ~ 0.91. Have stronger physical properties, abrasion resistance is good, has certain heat resistance; Has a certain impact resistance at room temperature and low temperature (below 5 ℃) under the poor impact resistance; Electric property, good water resistance and chemical resistance; Combustion will produce the smell of the oil, gelling and printing operations more difficult; Good heat resistance, in the absence of under the action of external force, can use for a long time under 150 ℃, but around 165 ℃ will melt;   Bad cold resistance, weather resistance, high rigidity, fire burn.
  PC (polycarbonate) : the specific gravity of 1.2. Good heat resistance (100 ~ 150 ℃), can use for a long time under 130 ℃; The characteristics of low temperature is also very good, - 180 ℃ is still not easy to crack; Electric property is good, not easy to change
Shape; Transparent appearance, good weatherability; When in direct sunlight is also very stable, the processing of oxidation rate is low; High impact resistance; Belongs to the non-toxic material, weak acid resistance; With the high voltage resistance, suitable for insulation products; To the weak organic solvent resistance; Poor resistance to bending fatigue strength, easy to produce stress cracking phenomenon; Poor heat sealing, alkali resistance, ketone, aromatic solvents, expansion in many organic solvents, and lead to stress cracking.
  ABS + PC, ABS and PC plastic blending first, and then melt injection molding, the characteristics of both ABS and PC, used in mobile phones, computers and laptops.
  Composite materials, composite materials are mainly ABS and PC or short glass fiber were mixed, then melt injection molding, the characteristics of both ABS and PC, and impact resistance, bending resistance, resistance to pressure load such as excellent mechanical properties.
NYLON (polyamide, PA) : high surface hardness, resistance to lubricity is good, not easy to cause uneven surface; Good chemical resistance, good oil resistance; Good impact resistance; Good electrical properties and low temperature resistant characteristics.
  Adding glass fiber to reinforce mechanical properties, such as impact resistance, bending resistance, stress resistance load, etc. Crystalline is good, because the cohesion of the resin is stronger so need and PP processing method. Meet the thermal deformation temperature: 160 ℃; on a standard scale Transparent level 146 ℃; Glass reinforced level above 200 ℃; NYLON12:145 ℃.

    2. Plastic appearance defects and repair

2.1 plastic cosmetic defects
  Commonly used in laptop computers more plastic parts for injection molding, because the mold design, material feeding, injection temperature, mold temperature, exhaust, etc., can cause the defects of plastic parts, therefore before painting must carry on the appearance quality of plastic material, judgement is returned, spraying or allow incoming repair.
  In this reference samsung component inspection specifications of plastic component in the terms and definitions of appearance defects, make coating engineer and technical service personnel can understand more defect and reason of the plastic substrate, and coating beautification cover defects to compensate for the substrate and coating technology. South Korea's samsung, for plastic injection molding components appearance defects of terms and definitions are as follows:
Seam weld line/cold: injection molding with the pin or molten plastic into the mold cavity around the center, or into two or more flow channel, the linear color defects in confluence, is caused by the cold material flow combined with.
  Flow mark: after mold cavity into the molten plastic to flow as the center of the thick line of different color surface, general system caused by the improper temperature and pressure.
  Shrink film/light: injection molding, because the product itself or its RIB (RIB) and column (BOSS) too thick, such as molten plastic product surface, the phenomenon of the sag during cooling, general system caused by uneven thickness or cooling too quickly and are not synchronized cooling.
Burrs/flash: also known as flash, refers to when the molten material into the mould clamping surface, if there is a gap, burrs formed in the material will flow into the gap.
  Black spots (different color) : material mix the foreign body, showing black dot on the surface phenomenon.
  Bleaching/dozen white: shaping with the impact on raw materials or components from other parts for dry involve stress caused by local appear white phenomenon.
Impurities/exception: materials appear on the surface or mixed with abnormal material in the products surface contamination phenomenon.
Crack/cracking: because of the internal stress or break of external shocks, etc.
  Short shot/material shortage: due to material not fully heating or mold cavity caused by injection pressure low material not completely filling injection phenomena.
  Touch scratches/marks: due to the local impact of external ke is printed on substrate or fine marks of the state of the phenomenon.
  Color: compared with the base color, caused by substrate management and condition changes color differences or different color sense.
Bubbles/holes: inside the von berg systeme thicker plastic injection into the gas hole or the floorboard of the formed due to shrinkage cavity.
  Crack: in the injection molding product surface caused by the stress of several fine lines of the phenomenon.
  Silver lines: silver streaks in the surface of the injection molding product, due to the mold temperature is low, raw water or caused by mixed with dissimilar materials.
 Stripping: similar to take off the paint in the surface layer of FRP products.: drag seal parts from the mold out when the delay caused by scratches phenomenon.
Gas lines: in the process of injection molding by ventilation and blackened fluxion phenomenon.

  2.2 the coating repair

  On incoming material of plastic components of the plastic coating factory, appearance quality checks for defective plastic components for rejection or allowed to repair. After the general method of repair is mainly fine sandpaper, darned defects of fixed-point spray or more comprehensive gush a few primer/finish. Commonly used repair method is as follows:

  (1). Sanding: the defective plastic, such as fusion line for sanding with high mesh sanding paper or water.
  (2) annealing: for there was stress annealing treatment of plastic parts in advance, in order to avoid the spraying or after baking plastic cracking.
  (3) deflashing: with box cutters and rolled rod to remove the plastic burrs.
  (4) the filling gun: the flawed, point injection in advance or after the spraying and again point injection.
  (5) bite base: in weak solvent or change the suitable material.
  (6) painting: by repainting increase film thickness and covering power to cover plastic appearance defects in itself.

  In fact, according to the author experience, through the after repair of coating factory improve the defects of plastic components, its efficiency is not high, should be from the front to do something about the plastic molding stage.

 3. Laptop plastic component coating and characteristics

  Now in the market more than normal laptop computers and laptops paint is 1 ~ 2 two-component PU paint, or monocomponent acrylic color lacquer + 1 out of 1 UV light paint such a process is given priority to. Also use only spray 1 more small component of monocomponent acrylic paint technology, portable computer plastic base internal coating conductive plastic paint. Shall be for the use of two-component PU paint majority. Two-component PU paint can be subdivided into general paint, metal paint, varnish coat and elastic softness coating + paint (primer), etc., in the introduction of UV light curing coatings with elastic soft feeling coatings.

3.1 UV light curing coatings
  Now commonly used by solvent thermoplastic acrylic primer coating system, then spray UV clear varnish. General primer with bright silver/silver/dark series, UV varnish to cover protection. There are bright silver color paint or white color paint, coating on all sorts of color varnish again, finally the UV varnish coat. The supporting system are shown in table 1. With the improvement of environmental protection call for, started using water-based one-component acrylic primer to cover the UV varnish.
  The hardness of one-component waterborne acrylic primer, just with the characteristics of UV curing coating high hardness (general requirements for at least 2 h hardness above), to improve the water paint hardness insufficient shortcomings, therefore, waterborne primer plus high hardness, fast curing, UV curing varnish coat without solvent is one of the fastest, the most environmental protection coating system.

3.2 elastic softness coating
  Two-component elastic softness coating is a special elastic resin and special elastic powder (now mostly no longer elastic powder) made from transparent elastic coating, its characteristics are as follows:
  (1) give coating elastic, soft leather feeling;
  (2) the scratch resistance and adhesion. Elastic softness coating can be widely used in mobile phones, laptops, home appliances, audio, cosmetics boxes, car accessories and other plastic coating. Its physical and chemical properties and solvent coatings.

4. Portable computer plastic coating and SOP

  4.1 small laptop shell plastic accessories (such as push button/power button/lamp pins, etc.) is generally not spray primer coating, spray only one line of monocomponent acrylic paint or two-component PU paint. Using artificial painting or reciprocating mechanical spraying.
The coating process is as follows:
  Substrate processing to use IPA (isopropyl alcohol) spray cleaning - > one-component two-component PU acrylic paint or paint to dry (60 ℃, 30 min) - quality control - forced drying (above 60 ℃, 120 min) and the packing.

  4.2 laptop shell plastic main parts (such as base/screen frame/frame cover/base, etc.) mainly used for laptop shell plastic main parts coating two-component polyurethane coatings, three kinds of softness coatings and uv-curable coatings, less using single-component acrylic coating. Here in uv curing coatings and elastic softness coating coating process as an example, the process is shown in figure 1 and figure 2.
UV light curing coating basic requirements: (1) clean type job shop, has closed spray (including oven and UV light curing oven); (2) the constant temperature and humidity, especially UV spray; (3) UV spray exhaust extraction system is better, or curing film easy generation sand point, dander, orange peel, flow adjustment, it contains air bubbles, etc. General UV topcoat painting very hard, if there is a sand point or dander, for defective parts polishing wax; Spray or rework after heavy, but the effect is not ideal. Generally small plastic spray paint, especially after spray UV lacquer film flawed simply discarded.

  4.3 spraying standard operating procedure (SOP)
  Laptops in real quantity antenatal spray paint factory, the engineering department engineers will first try to spray paint line actual small paint spray and try. If the computer company RD/ID (industrial design engineer) coatings are used for several times
A small paint trial cannot meet the requirements of color, appearance, and computer company internal coating physicochemical performance specification standard, stationary computer company RD may replace other coating or change this laptop using coating design specification parameters. The engineering department engineers after small try paint and spray, get actual operation parameters; Combined with paint of the coating product technical data provided by the laptop computer company, coating design and the quality specification to start design for spraying standard operating procedure (SOP), spray paint production standards as the basis. Laptop shell cover (Top) SOP.

   5. Spraying equipment

   For 3 c products OEM spraying plant powder spraying and painting two points, also have a spray and spray powder in the same factory but in different spraying line.
  Spray paint factory is painted metal spray paint line and plastic line. Larger electronic OEM factory in addition to painting, also contracted the upstream customers, such as samsung, LG, such as mold design and manufacturing, plastic injection molding, spraying, printing, the component composition, etc.
  Plastic portable computer spraying spraying equipment factory of plastic paint spraying workshop can be divided into artificial spraying line, automatic reciprocating spray line, coating line, spin coating to rail line and robot spraying line. Laptop small plastic accessories or group general using artificial spraying, automatic reciprocating spray or spraying manipulator.
  On the cover and the cover large plastic parts, such as mostly adopts automatic spraying.
Automatic spraying and automatic reciprocating spray, spin coating, mechanical arm, coating and spraying to rail.

6. conclusion
  Laptops use plastic coating is environmental protection, waterborne, solvent-free uv-curable coatings in the direction of development. Laptop computer market in the face of fierce competition, the upstream laptop design development engineers also stir all his brains on the shell material, appearance, function, color great pains. In addition to plastic material, other materials are also constantly updated. Plastic coating development engineer also to continuous innovation, to meet the requirements of users.

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