The common knowledge about die-cutting materials (part 1)

In the die-cutting industry, common die-cutting materials can be divided into eight categories: release materials, adhesive series materials, conductive shielding materials, surface protection materials, sealing/buffer materials, insulation flame retardant materials, waterproof and dustproof materials, and backlight module materials.

Release Materials

Release materials are generally used for isolation, filling, protection, tape release, product covers, etc. They have the advantage of easy removal. During the use, different release materials with different release force, color, and characteristics should be selected according to different applications and requirements.

Common release substrates mainly include: glassine paper, CCK clay-coated paper, supercalendered paper, coating film paper, PE film, PET film, OPP film, PC film, PS isolation film, PMMA release film, BOPP release film, PE release film, plastic film, TPX release film, PVC release film, PTFE release film, PET release film, single-silicone release film, polyester release film, PTFE release film, composite release film, high-temperature resistant release film, polyphenyl ether release film, PTFE isolation film, polyethylene release film, composite release film (composed of two or more materials), etc.

Release materials are mainly divided into lightweight, medium weight, and heavyweight.

▲ Substrate Glasin paper forming process

▲ Production of coated paper

▲ Coating products

The adhesive series materials

The earliest adhesive used in double-sided tape came from animals and plants. In the 19th century, rubber was the main component of the adhesive. Nowadays, various polymers are widely used as adhesives. The adhesive can stick things together because of the chemical bonds formed between its molecules and the objects to be connected. The composition of adhesives varies among different brands and types, and they are made of different polymers.

Adhesives can be classified into three categories based on their structure: non-substrate double-sided tape, substrate double-sided tape, and single-sided tape.

Non-substrate double-sided tape, such as acrylic adhesive film, is mainly made of acrylic adhesive, with a thickness of 0.05-0.15mm. A disadvantage is that it cannot be peeled off as a whole due to its inability to form a cohesive structure.

Substrate double-sided tape is represented by tissue paper double-sided tape, PET double-sided tape, and foam double-sided tape. Tissue paper double-sided tape is made of tissue paper and nonwoven fabric as substrates, with adhesive coated on both sides, and a thickness of 0.10-0.20mm. Nonwoven fabric is the most common substrate, with the advantages of strong flexibility and wide application range. Tissue paper substrate has the advantages of good strength and strong flexibility. PET double-sided tape is made of PET as the substrate, with adhesive coated on both sides, and a thickness of 0.01-0.25mm. It is transparent and thin. Foam double-sided tape is mainly made by coating adhesive on both sides of foam or by making acrylic foam into double-sided tape, with a thickness of 0.25-3.0mm. It has the advantages of resilience, balanced tension, and filling uneven surfaces.

Single-sided tape is made of materials such as PET, PE, BOPP, and PI as the substrate, with adhesive coated on one side, and the adhesive thickness is 0.03-0.15mm.

▲Structure of double-sided tape

Adhesives according to adhesive classification can be divided into: acrylic, synthetic rubber, rubber, silicone.

Acrylic, excellent durability, can be bonded to a variety of substances, short-term temperature resistance up to 230 degrees, the production process is relatively simple, the cost is moderate.

Synthetic rubber, has good adhesion to various materials, low impedance, low cost. But high and low temperature resistance, poor aging resistance.

Rubber, good initial viscosity, can be bonded to a variety of substances, low cost, but poor temperature resistance, generally not more than 90 degrees, poor chemical corrosion resistance, easy aging.

Silica gel has strong resistance to high and low temperatures (-100°-500°), aging resistance, suitable for bonding of low surface energy products, but the cost is high, the initial adhesion is low, and it is easy to react with strong alkali and hydrofluoric acid.

Adhesives according to the application method can be divided into: pressure sensitive adhesive, hot melt adhesive, conductive adhesive.

Pressure sensitive adhesive, can be applied to a certain pressure can be bonded, no solvent or heating, can provide a durable and reliable adhesion (usually 72 hours to reach the maximum adhesion).

Hot melt adhesive, the application of hi needs to apply a certain temperature, usually about 120 degrees, so that the glue melts, producing reversible (thermoplastic crosslinking) or irreversible (thermosetting crosslinking) reaction, so as to achieve a strong adhesive force.

Conductive adhesive, adding conductive metal particles or fibers to the adhesive, or coating adhesive with conductive material as the base material to form a tape with different directions of conductive.

Conductive shielding material

Conductive shielding materials are mainly divided into three categories, mainly conductive adhesive, conductive foam, conductive cloth shielding.

Conductive adhesive refers to a kind of adhesive with conductive property. Conductive adhesive is a kind of adhesive with certain conductive property after curing or drying. It is usually composed of matrix resin and conductive filler, i.e. conductive particles. Through the bonding effect of matrix resin, the conductive particles are combined together to form a conductive connection and realize the conductive connection of the bonded material. Since the base resin of the conductive adhesive is a adhesive, the appropriate curing temperature can be selected for bonding, and at the same time, due to the miniaturization of electronic components, miniaturization and the rapid development of high density and high integration of printed circuit boards, the conductive adhesive can be made into a slurry to achieve high line resolution. The conductive adhesive process is simple, easy to operate, and can improve production efficiency, so the conductive adhesive is an ideal choice to replace lead tin welding and realize conductive connection. Generally used in circuit board grounding. FPC connection is used.

Conductive foam, which is made of elastic PU foam wrapped by textile fiber cloth containing metal coating, has good elastic and conductive properties. It is mainly suitable for occasions that cannot provide greater pressure, and plays a good role in battery sealing. In the processing can be processed according to customer requirements of different shapes and sizes, widely used in a variety of electronic products EMI prevention. Conductive foam is divided into ordinary conductive foam and all-round conductive foam, ordinary conductive foam is mainly conductive by X, Y axis, and all-round conductive foam X, Y, Z can be conductive.

Conductive cloth shielding, with highly metallized nylon and polyester materials as the base material, has the same excellent electrical conductivity as metal, while having good toughness and winding performance, back conductive adhesive is an ideal material for various electronic appliances and communication equipment shielding and grounding of circuit boards or various surfaces is also very suitable.

▲ Ordinary conductive foam

▲ All-round conductive foam

▲ Conductive cloth

▲ Conductive adhesive

Surface protection series materials

The protective film can be divided into four categories according to its use, which are digital product protective film, automobile protective film, household protective film, food preservation protective film and so on.

According to the material classification can be divided into seven categories, respectively, PP material, PVC material, PET material, AR material, PE material, OPP material, OCA material.

The protective film of PP material first appeared on the market, the chemical name is polypropylene, without any adsorption capacity, generally bonded with glue, after tearing off the screen surface will leave a mark of glue, now basically has been eliminated.

The protective film of PVC material itself has a soft texture and is easy to paste, but the material is thick and the light transmission is not good, making the screen look more hazy. In addition, it is also easy to yellow out oil with the change of temperature, and its service life is short.

PET material protective film is the most common kind of protective paste on the market, the texture is relatively hard, scratch resistant, long-term use will not turn yellow oil. However, relying on electrostatic adsorption, it is easy to foam and fall off. The price is more expensive than PVC, but the work and packaging of PET material protection stickers are more beautiful.

OPP material from the appearance of the protective film is closer to the PET protective film, its hardness is larger, by a certain flame retardant, but the paste effect is poor, rarely used in the general market.

The main raw material of the protective film of PE material is LLDPE, which is soft and has certain stretchability. The general thickness is 0.05mm-0.15mm, and the viscosity varies from 5G-500G according to different requirements.

The AR film is one of the best screen protectors known on the market. AR is a synthetic material, generally divided into three layers, silicone for the adsorption layer, PET for the middle layer, the outer layer for the special treatment layer. The special treatment layer is divided into AG treatment layer and HG treatment layer, AG for anti-glare treatment and HG for hardness treatment.

OCA material protective film from the appearance of no difference with other materials, but OCA material protective film produced in Japan, is now widely used in Apple mobile phones, in light and hardness than other materials are better, is now the most popular material to collect protective film.

▲ Protective film

Seal/buffer series materials

Foam according to the material classification can be divided into polyethylene foam, polyester foam, rubber foam:

Polyethylene foam is mainly PE foam and EVA foam two categories, of which PE foam is mainly through chemical crosslinking and electronic crosslinking.

Polyester foam is mainly polyether foam and polyurethane foam two categories, both of which are formed by chemical foaming and physical foaming.

Rubber foam mainly includes CR foam (neoprene rubber), NR foam (nitrile rubber), SBR foam (styrene butadiene rubber), EPDM foam (EPDM rubber)

According to the foam structure can be divided into open cell foam and closed cell foam:

Porous foam cotton soft, high water absorption, high compression rate, suitable for sound absorption sealing applications, such as compression sponges for headphones and air conditioning seals.

Closed cell foam is independent foam, low compression residual rate, low water absorption, good heat insulation and buffer performance, good dust, suitable for electronic products sealed dust, waterproof shock absorption and so on.

Sealing/buffering series material features:

Low pressure very good shielding effect, shielding efficiency of more than 90dB;

Flexible, light weight;

Anti-corrosion nickel coating can prevent electrochemical corrosion;

Low surface contact resistance;

Rapid pressure sensitive fixation;

Customer can specify the length;

A wide selection of sections;

UL grade fire protection;

Can paste Mylar sheet (valet double-sided tape) product quality is stable;

Heat resistant pressure, not easy to fall off, high tensile strength;

After the product is installed, the temperature is from -20℃ to 80℃.

Cycle cycle test 72 hours to maintain the quality;

It has a series of characteristics, such as easy to use, flexible bending, ultra-thin volume and reliable performance.

Insulating and flame retardant materials

Insulation and flame retardant materials mainly include: PC, PVC (such as electrical tape), PET, ITW-FORMEX material (PP), fast bus sheet and so on.

Commonly used brands are Toray, Mitsubishi, Jane, GE, SKC, ITW, DuPont and so on.

Insulating flame retardant materials mainly have the following four characteristics:

Excellent electrical insulation performance;

Meet UL standards (most can reach 94V-0 fire rating);

High voltage resistance - can work in a high temperature environment of more than 100 degrees Celsius for a long time;

Some non-halogen flame retardants do not cause environmental pollution (there are still halogenated flame retardants in the market).

Flame retardant standard, UL94 test a total of five kinds:

Level B horizontal combustion experiment;

94-5-V vertical combustion test;

Flame spread index experiment with radiant panel;

94VTM-0, 94VTM-1, 94VTM-2 vertical combustion test.

Flame retardant rating:

[align=left] The horizontal sample with HB thickness < 3mm burns slowly, and the combustion speed < 76mm/minV-0 the vertical sample stops burning within 10 seconds; No droplet V-1 vertical sample is allowed to stop burning within 30 seconds; No droplet V-2 vertical sample is allowed to stop burning within 30 seconds; Allow combustion droplets of 5V to burn the test rod 5 times, each time the flame is larger than the flame in the V test, each lasting 5 seconds. The combustion stops in 60 seconds.

Sample burned through (produces a hole) 5VA sample not burned through (does not produce a hole) -UL highest grade

Waterproof, dust-proof series material

There are five categories of mesh gauze, such as cotton gauze, silk gauze, single yarn polyester mesh, nylon wire mesh and stainless steel mesh.

▲ Stainless steel mesh

Fabric according to the structure classification, can be divided into non-woven fabric, filter mesh, punching mesh.

Non-woven fabric is a nonwoven fabric, the textile short fiber or filament is oriented or randomly braced to form a fiber network structure, and then the mechanical, thermal bonding or chemical methods are used to strengthen it, and the waterproof treatment increases the tension to achieve the waterproof effect.

The filter is an industrial fabric made of synthetic fibers and other raw materials, with uniform and stable air holes on the surface, and with screening and filtering functions.

Punching mesh is the application of stamping die according to the design of emptiness, aperture, hole distance and opening rate of different materials cold blanking, has a unique visual effect.

Classified by material, non-woven fabrics include polypropylene (PP), polyester (PET), cotton (PA) and acrylic (PVN), which have the advantages of air permeability, dust proof, heat preservation, waterproof and low price, but due to non-directionality, the strength is worse than that of textile fabrics, and the acoustic test is unstable. Filter has polyester (PET), cotton fiber (PA), stainless steel (SS), polyester tensile strength, good heat resistance; Cotton fiber suitable for printing, good alkaline resistance; Stainless steel has the best strength, but is expensive; The punching mesh has polyester PET, the minimum hole can be punched 0.3mm; Polycarbonate PC is not suitable for micropores below 0.5mm, stainless steel, etc.

Backlight module series materials

As one of the key components of the LCD panel, the backlight module provides sufficient brightness and distributes a uniform light source to make the display display images normally.

The key components of the backlight module are mainly composed of Light source and Light guide plate), rubber frame (housing), Reflector (Reflector), Diffuser (Diffuser), enhancement (BEF, prism), black and white adhesive (Curtain Tape), etc.

▲ Basic structure of backlight group

▲ B/L structure

▲ B/L diaphragm structure

In conclusion, the above is our summary of the basic knowledge of commonly used die-cutting materials, as a professional die-cutting engineer, only in the basic materials are very familiar with the basis, in order to die-cutting a good product. Next week, we will also share the application direction and application plan of specific materials of commonly used die-cutting materials. I hope our sharing will be helpful to you.