There Are Specific Types of PCB Boards

What are the specific types of PCB boards? 

According to the grade level from bottom to high divided as follows:

94HB-94VO-22F-CIM-1-CIM-3-FR-4

The details are as follows:

94HB: ordinary cardboard, not fireproof (the lowest grade material, die punching, can not be used as a power board);

94V0: flame retardant cardboard (die punching);

22F: single-sided semi-glass fiber board (die punching);

Cim-1: single glass fiber board (must be computer drilling, can not die punching);

Cim-3: double-sided half-glass fiber board (in addition to double-sided cardboard is the lowest end of the double-panel material, simple double-panel can use this material, than FR-4 will be cheaper 5~10 yuan/square meter);

FR-4: Double-sided fiberglass board: The circuit board must be flame resistant, can not burn at a certain temperature, can only soften. At this time, the temperature point is called the glass transition temperature (Tg point), and this value is related to the size stability of the PCB board.

①At present, China's national standards for the classification of substrate materials pcb board are：GB／T4721—47221992 及 GB4723—4725—1992.The standard of copper clad foil plate in Taiwan of China is CNS standard.

② Main standards of other national standards are: JIS standards in Japan, ASTM, NEMA, MIL, IPc, ANSI, UL standards in the United States, Bs standards in the United Kingdom, DIN, VDE standards in Germany, NFC and UTE standards in France, CSA standards in Canada, and AS standards in Australia. The FOCT standard of the former Soviet Union, the international IEC standard, etc.

According to PCB board reinforcement materials are generally divided into the following categories:

1, phenolic PCB paper substrate

Because this PCB board is composed of pulp wood pulp, etc., it is sometimes also become cardboard, V0 board, flame retardant board and 94HB, etc. Its main material is wood pulp fiber paper, pressurized by phenolic resin and synthesized a PCB board.

This paper substrate is characterized by no fire, can be punched processing, low cost, cheap price, relatively small density. Phenolic paper substrate we often see XPC, FR-1, FR-2, FE-3 and so on. And 94V0 belongs to flame retardant cardboard, is fireproof.

2, composite PCB substrate

This also becomes a powder board, with wood pulp fiber paper or cotton pulp fiber paper as the reinforcement material, while supplemented by glass fiber cloth as the surface reinforcement material, both materials are made of flame retardant epoxy resin. There are single-side semi-glass fiber 22F, CIM-1 and double-side semi-glass fiber plate CIM-3, among which CIM-1 and CIM-3 are the most common composite base copper clad plates at present.

3, glass fiber PCB substrate

Sometimes it is also known as epoxy board, glass fiber board, FR4, fiberboard, etc., which uses epoxy resin as a binder and glass fiber cloth as a reinforcing material. This circuit board has a high operating temperature, is little affected by the environment, and is often used in double-sided PCB, but the price is more expensive than the composite PCB substrate, and the common thickness is 1.6MM. The substrate is suitable for various power supply boards, high-rise circuit boards, and is widely used in computers and peripheral equipment, communication equipment and so on.

4. Other substrates

In addition to the three commonly seen above, there are also metal substrates and laminated multilayer boards (BUM).

1. Substrate: The substrate of PCB board refers to the material used in the non-conductor part of the circuit board, mainly glass fiber cloth, epoxy resin, polyimide and so on. Among them, glass fiber cloth is widely used in the manufacture of double panel and multi-layer board, while epoxy resin and polyimide are used in the manufacture of high-density multi-layer board.

2. Copper foil: Copper foil is the material used in the conductive part of the PCB board. It is processed by processes such as electroless copper plating or mechanical copper pressing, and chemically treated on the surface to improve its weldability and corrosion resistance. Copper foil thickness is usually 0.5oz-6oz (1oz=1.4mil), and different thickens are suitable for different types of circuit board designs.

3. Hardener: Hardener is the key material for epoxy resin curing in PCB board. It forms a 3D network structure by reacting with epoxy resin, so that the PCB board has good mechanical properties and high temperature resistance.

4. Solder resistance ink: Solder resistance ink is a material coated on the surface of the PCB board to protect the areas on the circuit board that do not need to be welded. It can improve the insulation performance and corrosion resistance of the PCB board, while also reducing problems such as short circuit and leakage.

5. Printing ink: Printing ink is a material used to print circuit patterns on the surface of the PCB board. It is usually processed using UV light curing technology and coated to the substrate surface by means of screen printing or spraying.

PCB board quality introduction

Printed circuit boards are important components of electrical or electronic devices manufactured from Copper foil substrate (copp-clad Laminate) as raw materials, so downstream operators engaged in circuit boards must have an understanding of the substrate: what kinds of substrates are available, how they are manufactured, and what products are used in them. They each have those advantages and disadvantages, so that you can choose the appropriate substrate. Table 3.1 briefly lists the applications of different substrates. Substrate industry is a basic industry of materials, It is a Composite material composed of a dielectric layer (Resin Resin, Glass fiber) and a high-purity conductor (Copper foil), and the theory and practice involved are not less than the production of the circuit board itself. The following is a simple discussion of these two main components.

At present, there are many types of resin used in circuit boards, such as phenolic resin (Phonetic), Epoxy resin, polyimide resin (Polyamide) Pce), Polytetrafluorethylene (PTFE or TEFLON), Bismaleimide Triazine (BT) and other resins are Thermosetted plastics Resin).

The Phenolic Resin

It is the first successfully developed and commercialized polymer. It is a synthetic material made of two inexpensive chemicals, liquid phenol and liquid formaldehyde (commonly known as formalin), which undergo a continuous reaction of Crosslinkage under acidic or alkaline catalytic conditions and harden into a solid. Its reaction chemical formula is shown in Figure 3.1. In 1910, a company called Bakelite added canvas fiber to make a hard, strong, insulating and good material called Bakelite, commonly known as cork board or urea board. The NEMA-Nationl Electrical Manufacturers Association (NEMA-Nationl Electrical Manufacturers Association) uses different combinations with different numbering codes for industry use. Now the phenolic resin products are listed, as table NEMA for phenolic resin board classification and code.

The first "X" in the paper substrate is for mechanical use, and the second "X" is for electrical use. The third "X" indicates places where radio waves and high humidity are available. "P" means heat is needed to Punchable the board, otherwise the material will break, "C" means that it can be cold punchable, and "FR" means that the resin adds non-flammable substances to make the substrate Flame Retardent or Flame resistance.

The best-selling paper boards are XXXPC and FR-2. The former can be made into a type at a temperature above 25 ℃ and a thickness below.062IN. The latter combination is exactly the same as before, but the antimony trioxide is added to the resin to increase its flammability. The following are some of the more commonly used paper substrates and their special uses:

Paper substrate is often used

a. XPC Grade: Usually used in low voltage, low current will not cause fire source of consumer electronic products, such as toys, portable radio, telephone, calculator, remote control and clocks and so on. UL94 requires only HB flame retardant Grade for XPC Grade.

b. FR-1 Grade: Electrical and flame resistance is better than XPC Grade, widely used in electrical appliances with slightly higher current and voltage than XPC Grade, such as color TV, monitor, VTR, home stereo, washing machine and vacuum cleaner, etc. UL94 requires FR-1 flame resistance V-0, V-1 and V-2 different grades, but because the price difference between the three grades is not large, and for safety reasons, the electrical industry almost all use V-0 grade plates.

c. FR-2 Grade: Compared with FR-1, except for slightly higher electrical performance requirements, other physical properties are not special, in recent years, in the paper substrate industry efforts to improve FR-1 technology,FR-1 and FR-2 nature boundary has gradually blurred,FR-2 grade sheet may be FR-1 in the near future under high price factors To be replaced.

Other special uses:

a. Paper substrate for copper plated through holes

The main purpose is to plan to replace some FR-4 plates with low physical property requirements in order to reduce the  cost of PCB.

b. Paper substrate for silver perforation

At present,  the most popular replacement part of the physical property requirements are not very high FR-4 as a through hole plate,  that is, a Silver hole with a paper substrate printed circuit board on both sides of the line,  can be directly by printing the Silver Paste on the hole wall, through high temperature hardening, that is,  become a through body, unlike the general FR-4 plate copper plating through Holes, need to go through activation,  chemical copper, copper plating, tin lead and other complicated procedures.

Substrate quality

1) Dimensional stability:

In addition to paying attention to the X, Y axis (fiber direction and transverse direction), pay more attention to the Z axis (plate thickness direction), due to thermal expansion, cold contraction and heating reduction factors are easy to cause the fracture of the silver glue conductor.

2) Electrical and water absorption: many insulators in the moisture absorption state, reduce the insulation, so as to provide the metal in the potential difference trend power shift phenomenon,FR-4 in dimensional safety, electrical and water absorption are better than FR-1 and XPC, so the production of silver perforated printed circuit board, to choose a special FR-1 and XPC paper substrate. The board.

Conductor material 

1) Conductor material Silver and carbon ink perforated printed circuit conduction is the use of silver and graphite particles embedded in the polymer body, through the contact of the particles to conduct electricity, and copper plated through the printed circuit board, by the copper itself is a coherent crystal and produce very smooth conductivity.

2) Ductility:

Copper plated through the hole is a continuous crystal, has very good ductility, not like silver, carbon ink glue in thermal expansion and contraction, easy to occur interface separation and reduce the conductivity. 3) migration: Silver and copper are all metallic materials, which are prone to oxidation and reduction resulting in rusting and Migration. Due to the difference in potential difference, silver is more prone to Silver Migration than copper under the potential difference trend.

Carbon Through Hole (Carbon Through Hole) paper substrate.

The graphite in carbon ink does not have the migration characteristics like silver, and the role of graphite is only a simple signal transmitter, so the PCB industry has no special requirements for the laminate in addition to the adhesion and warping of carbon ink glue and the substrate. Because graphite has good wear resistance, Carbon Paste was first used to replace the gold plating on Key pads and gold fingers, and then extended to act as a jumper. The load current of the carbon ink perforated printed circuit board is usually designed very low, so the industry mostly uses the XPC grade, as for the thickness, considering the factors of light, thin, short, small and printed perforation, it is common to choose 0.8, 1.0 or 1.2mm thick plate.

room temperature punching paper substrate

Characterized by the surface temperature of the paper substrate is about 40 ° C below, can be used as a Pitch of 1.78mm IC dense hole punching die, hole cracks will not occur, and to reduce the cooling of the paper substrate during the punching die caused by the precision of the line deviation, this kind of paper substrate is very suitable for fine lines and large area of printed circuit boards.

Anti-leakage voltage (Anti-Track) with paper substrate

The more refined human life, the more the requirements for items and the shorter and thinner, when the circuit design of the printed circuit board is more dense, the line distance is smaller, and under the requirements of high functionality, the current load becomes larger Then between the lines is prone to arc damage the insulation of the substrate caused by leakage, paper substrate industry in order to solve this problem, there is a supply of special adhesive copper foil made of anti-leakage voltage with paper substrate

Epoxy Resin

Epoxy Resin is the most widely used substrate in the PCB industry. In its liquid state it is called Varnish or A-stage, The glass cloth is semi-dried into film after dipping and then softened and liquefied at high temperature to show adhesion and used for double-sided substrate production or multi-layer plate pressing called B-stage prepreg, and the final state that cannot be recovered by pressing and rehardening is called C-stage.

Composition and properties of traditional epoxy resin

The monomer of epoxy resin used in substrate has always been A polymer formed by Bisphenol A and Epichlorohydrin using dicy as bridging agent. To pass the Flammability test, the above resin, still in liquid form, is reacted with Tetrabromo-Bisphenol A to become the conventional epoxy best known as FR-4. The main ingredients of the product are listed below: Monomer -Bisphenol A, Epichlorohydrin

Bridging agent (i.e. hardener) - Dicyandiamide for short Dicy

Accelerator -Benzyl-Dimethylamine (BDMA) and 2-Methylimidazole (2-MI)

Ethylene glycol monomethy ether(EGMME) Dimethy formamide (DMF) and diluent Acetone,MEK.

Fillers (Additive) - calcium carbonate, silicides, and aluminum hydroxide or compounds increase fire resistance. The filler can adjust its Tg.

Monomers and low molecular weight resins

Typical traditional resins are commonly referred to as Difunctional Epoxy resins, as shown in Figure 3.2. In order to achieve the purpose of safe use, bromine atoms are added to the molecular structure of the resin, so that the combination of some carbon bromine can produce a non-flammable effect. That is to say, when there is a burning condition or environment, it is not easy to ignite, in case it has been ignited after the combustion environment disappears, it can extinguish itself and no longer continue to burn. Figure 3.3. This flammability material is termed FR-4 in the NEMA code (sex is G-10 in the NEMA code for non-brominated resins) The advantages of this brominated epoxy resin are very high, its very low dielectric constant, strong adhesion to copper foils and very good flexible strength in combination with fibreglass, etc.

Bridging agent (hardener)

The bridging agent of epoxy resin has always been Dicey, which is a latent (latent) catalyst that plays its bridging role at a high temperature of 160 ° C and is very stable at room temperature, so that the film of multi-layer board B-stage can not be stored. However, Dicey has many shortcomings, the first is the water absorption (Hygroscopicity), the second is the insolubility. Insoluble naturally difficult to function in liquid resin. Early substrate manufacturers did not understand the downstream circuit board assembly industry problems, dicey grinding at that time is not very fine, its insoluble part mixed in the substrate, after a long time of accumulation of water absorption will occur needle-like recrystallization, resulting in many board explosion problems. Of course, the current substrate manufacturers are well aware of its seriousness, so they have improved this point.

Accelerant

To accelerate the bridging reaction between epoxy and dicey, the two most commonly used are BDMA and 2-MI.

Tg glass transition temperature

Due to the gradual rise in temperature, the physical properties of polymer gradually change, from the amorphous or partially crystalline hard and brittle glass-like substances at room temperature to a very high viscosity, soft as rubber in general, another state. The Tg of traditional FR4 is about 115-120℃, which has been used for many years, but in recent years, due to the increasingly high performance requirements of electronic products, the characteristics of the material are also increasingly demanding, such as moisture resistance, chemical resistance, solvent resistance, heat resistance, dimensional stability, etc., are required to be improved to adapt to a wider range of uses. These properties are related to the Tg of the resin, and the above properties are also naturally improved after the increase of Tg. For example, after Tg is increased, a. Its heat resistance is enhanced, and the expansion of the substrate in the X and Y directions is reduced, so that the adhesion between the copper wire and the substrate will not weaken too much after heating, so that the line has better adhesion. When the expansion in the Z direction is reduced, the wall of the through hole is not easy to be broken by the substrate after being heated.c. When Tg is increased, the density of the bridge in the resin must be greatly increased, which makes it have better water resistance and solvent resistance, and makes the board less prone to white spots or weave exposure after being heated, and has better strength and dielectric property. As for dimensional stability, it is even more important due to the strict requirements of automatic insertion or surface assembly. Therefore, in recent years, how to improve the Tg of epoxy resin is the priority pursued by the substrate.

FR4 refractory epoxy resin

Traditional epoxy resins encounter high temperature fire, if there is no external factor to extinguish, will continue to burn until the hydrocarbon oxygen or nitrogen in the molecule is burned. If bromine is substituted for hydrogen in its molecule, a part of the combustible carbon-hydrogen bond compound can be changed into a non-combustible carbon-bromine bond compound, which can greatly reduce its flammability. The flammability of this brominated resin is naturally enhanced a lot, but it reduces the adhesion between the resin and copper and glass, and in case of fire, it will release highly toxic bromine gas, which will bring adverse consequences.

Multifunctional Epoxy (High-performance epoxy)

Traditional FR4 is no longer sufficient for today's high-performance circuit boards, so a variety of different resins are mixed with the original epoxy resin to enhance the various properties of its substrate.

Novolac

The first phenolic resins to be introduced were called Novolacs, and the esters formed from Novolac and epichlorohydrin were called Epoxy Novolacs, as shown in Figure 3.4. By mixing this polymer into FR4 resin, its water resistance, chemical resistance and dimensional stability can be greatly improved, and Tg is also increased. The disadvantage is that the hardness and brittleness of phenolic resin itself are very high and easy to drill, and the chemical resistance is enhanced, which is difficult to remove the glue caused by drilling and cause trouble in the multi-layer PTH process.

Tetrafunctional Epoxy

Another common addition to FR4 is the so-called Tetrafunctional Epoxy Resin. It is different from the traditional "dual-function" epoxy resin in that it has a three-dimensional space bridge, as shown in Figure 3.5. Tg has a higher energy resistance to poor thermal environment, and its resistance to solvents, chemical resistance, moisture resistance and dimensional stability are much better, and it does not have shortcomings like Novolac. It was first introduced by an American substrate factory called Polyclad. Another advantage of four-function over Novolac is better uniform mixing. In order to maintain the convenience of multi-layer plate removal of glue residue, this four-function substrate is best baked in the oven at 160 ° C for 2-4 hours after drilling, so that the resin exposed to the hole wall produces oxidation, and the oxidized resin is easier to be corroded, and it also increases the further bridge polymerization of the resin, which is also helpful for the later process. Because of the brittleness, special attention should be paid to drilling.

Neither of the above two additive resins can be brominated, so the addition of general FR4 will reduce its flame resistance.

A. Polymer consisting

Mainly of Bismaleimide and Methylene Dianiline reaction.

B.advantage

The adaptation of the temperature of the circuit board will become more and more important, some special high-temperature boards are not capable of epoxy resins, the Tg of the traditional FR4 is about 120 ° C, and even the high-function FR4 only reaches 180-190 ° C, which is still a long distance from the 260 ° C of polyimide. The good properties of PI at high temperature, such as good flexibility, tear strength of copper foil, chemical resistance, dielectric property, dimensional stability are much better than FR4. It is not easy to produce glue residue when drilling, and the connection between the inner layer and the hole wall is naturally better than FR4. And because of good heat resistance, its size changes very little, in terms of X and Y direction changes, it is more favorable to the fine line, and will not reduce the adhesion between the copper sheet due to too much expansion. In terms of Z direction, it can greatly reduce the chance of fracture of the copper layer of the hole wall.

C. Disadvantages:

It is not easy to brominate, and it is not easy to meet the flame retardant requirements of UL94 V-0. The adhesive force between the layer and the layer itself, or between the copper foil, is poor, not as strong as the epoxy resin, and the flexibility is poor.

It performs poorly at room temperature, having Hygroscopic properties, poor adhesion and ductility. d. The solvent used in Varnish (also known as raw glue, liquid resin) has a high boiling point, is not easy to finish, and is easy to produce the phenomenon of delamination at high temperature. And the liquidity is not good, pressing is not easy to fill the dead corners. e. The current price is still very expensive about 2-3 times of FR4, so only military board or Rigid Flex board can be used. In the US Army specification MIL-P-13949H, the polyimide resin substrate code is GI.3.1.2.4 Polytetrafluoron (PTFE)

The full name is Polyterafluoroethylene, and the product with which PTFE fiber is drawn is called Teflon Teflon, which is characterized by its high Impedance and cannot be replaced for high frequency microwave communication purposes "GT", "GX", and "GY" three materials, are glass fiber reinforcement type, its commercial substrate is made by 3M company, this material can not be put into production in large quantities, the reasons are: A. PTFE resin and glass fiber adhesion problems; This resin is difficult to penetrate into the glass beam, due to its strong chemical resistance, many wet processes can not make it react and activate, the copper hole wall obtained during plating through the hole can not be fixed on the substrate, it is difficult to pass the solid strength test 4.8.4.4 in MILP-55110E. Because the glass bundle is not filled with resin, it is easy to cause copper in the glass (Wicking) when plating through the hole, affecting the reliability of the board. B. The molecular structure of this tetrafluoroethylene material is very strong and can not be attacked by general mechanical or chemical methods, and only the electroslurry method is used for corrosion back. C. Tg is very low, only 19 degrees c, so it is flexible at room temperature, and also makes the adhesion and dimensional stability of the line is not good. Table is a comparison of substrate properties of four different resins. 3.1.2.5 BT/EPOXY resin

BT resin is also a thermosetting resin, which was developed by Mitsubishi Gas Chemical Co. in Japan in 1980. It is made of Bismaleimide and Trigzine Resin monomer. The reaction is shown in Figure 3.8.BT resin is usually mixed with epoxy resin to make the substrate. A. Advantages

a. The Tg point is as high as 180℃, the heat resistance is very good, and the peel Strength and flexible strength of the BT plate and copper foil are also very ideal. It can be refractory treatment to meet the requirements of UL94V-0. c. The dielectric constant and dispersion factor are small, so it is very advantageous for high-frequency and high-speed transmission boards. Good chemical resistance and solvent resistance e. good insulation B. The circuit board designed by a. COB will make the surface of the board soft and lead to wire failure due to the high temperature of the wire bonding process. BT/EPOXY high-performance panels can overcome this. b. BGA,PGA, In semiconductor packaging testing such as MCM-Ls, there are two very important common problems, one is the leakage phenomenon, or CAF(Conductive Anodic Filament), and the other is the popcorn phenomenon (impaction by moisture and high temperature). 3.1.2.6 Cyanate Ester Resin was first used in PCB substrates in 1970 and is currently manufactured by Chiba Geigy. The reaction formula is shown in Figure 3.9. A. Advantages A. Tg can reach 250℃, which is used for very thick multi-layer board b. Very low permittivity (2.5~3.1) can be applied to high speed products.

B. Problem A. High brittleness after hardening. b. Sensitive to humidity and may even react with water. 3.1.2 Glass fiber 3.1.2.1 Introduction The function of Fiberglass in PCB substrate is as a reinforcing material. There are other reinforcing materials for the substrate, such as paper substrates, Kelvar(Polyamide) fibers, and Quartz fibers. Only the largest glass fibers are discussed in this section. Glass itself is a mixture, and its composition is shown in the table. It is a number of inorganic substances fused at high temperature, and then cooled by drawing wire into a hard object with an amorphous structure. This substance has been used for thousands of years. Fibrous use dates back to the 17th century. It was the joint research efforts of Owen-Illinois and Corning Glass Works that led to the formation of Owens-Corning Fiberglas Corporation in 1939. 3.1.2.2 Glass fiber can be divided into two kinds of glass fiber, one is Continuous (Continuous) fiber and the other is discontinuous (discontinuous) fiber, the former is used to weave glass cloth (Fabric), the latter is made into sheet glass Mat (Mat).FR4 and other substrates, that is, the former is used,CEM3 substrate is used

A. Characteristics of glass fiber The composition of the original melt-melted glass is different, will affect the characteristics of glass fiber, the difference of different components, the table has A detailed difference, and each has its own unique and different applications. According to the different composition (see table), the grade of glass can be divided into four commodities: grade A for high alkaline, grade C for chemical resistance, grade E for electronic use, and grade S for high strength. The E-class glass used in the circuit board is mainly because its dielectric properties are better than the other three.

Some common characteristics of glass fibers are described below:

a. High strength: Compared with other textile fibers, glass has extremely high strength. In some applications, the strength/weight ratio even exceeds that of wire.b. Resistance to heat and fire: Fiberglass is inorganic and therefore does not burn. Chemical resistance: Resistant to most chemicals, but also not for mold, bacterial infiltration and insect damage. Moisture resistance: Glass does not absorb water and retains its mechanical strength even in very humid environments. Thermal properties: Glass fiber has a very low coefficient of linear expansion and a high coefficient of thermal conductivity, so it has excellent performance in high temperature environments. Electrical property: Due to the non-conductivity of glass fiber, it is a good choice of insulating material. The most important thing about the E-class glass selected for PCB substrate is its very excellent water resistance. Therefore, in a very humid and harsh environment, it still retains very good electrical transitivity as well as dimensional stability. - Glass fiber cloth production: Glass fiber cloth production is a series of professional and huge investment process, which is not discussed in this chapter. 3.2 copper foil (copper foil) early line design is thick and wide, thickness requirements are not picky, but evolved to today's line width of 3,4mil, or even finer (now there are factories in China to develop 1 mil line width), resistance requirements are strict. Tear strength, surface Profile, etc. are also specified in detail. 3.2.1 Traditional copper foil 3.2.1.1 rolling Method (Rolled-or Wrought Method) was made of copper blocks by multiple rolling, and the width of the rolled was limited by technology and was difficult to meet the requirements of standard size substrate (3 feet *4 feet). And it is easy to cause scrap in the rolling process, because the surface roughness is not enough, so the ability to combine with the resin is not good, and the stress in the manufacturing process needs to be tempered by Heat treatment or Annealing, so its cost is higher. A. Advantages. a. High Ductility, excellent reliability for FPC in dynamic environment. Low-profile surfaces with Low Surface edges are a niche for some Microwave electronics applications. B. Disadvantages. a. Poor adhesion to the substrate. b. High cost. c. The width is limited due to technical problems. 3.2.1.2 The Electrodeposited Method is the most commonly used copper foil on the substrate is ED copper. Using a variety of discarded wires and cables to melt into copper sulfate plating solution, in a special deep underground large plating bath, anode and cathode distance is very short, at a very high speed impulse plating solution, with a high current density of 600 ASF, Columnar crystalline copper layer is plated on the surface is very smooth and passivated. Stainless steel Drum Drum, due to the passivated stainless steel drum on the copper layer is not good, so the plating surface can be torn off from the wheel, so plated continuous copper layer, can be different thickness of copper foil by the speed of the wheel, current density, affixed to the smooth copper foil surface of the Drum side, called the drum side. The rough crystalline surface on the other side of the bath is called the Matte side. This copper foil: A. advantages a. cheap price b. available in various sizes and thicknesses. B. Disadvantages. a. poor ductility. b. Extremely high stress, unable to bend and easy to break. 3.2.1.3 Thickness unit

Generally, in order to calculate the cost and facilitate pricing, the weight per square foot is used as the calculation unit of thickness, such as 1.0 Ounce (oz) is defined as a square foot area covered with a copper foil weight of 1 oz (28.35g) of the copper layer thickness. Unit conversion 35 micron or 1.35 mil. The general thickness of 1 oz and 1/2 oz and ultra-thin copper foil can reach 1/4 oz, or less. 3.2.2 Introduction and development direction of new copper foil 3.2.2.1 Ultra-thin copper foil

Generally speaking, thin copper foil refers to 0.5 oz (17.5 micron) below, and the thickness of the three tables is called ultra-thin copper foil 3/8 oz below because it is too thin and not easy to operate, so it needs to add a Carrier to do various operations (called composite copper) foil), otherwise it's easy to cause damage. There are two types of carriers used, one is the traditional ED copper foil as the carrier, the thickness of about 2.1 mil. Another type of carrier is aluminum foil, thickness of about 3 mil. The carrier must be torn away before use. One of the most difficult problems with ultra-thin copper foil is its "Porosity," or porosity, because it is too thin to be completely filled when electroplated. The remedy is to reduce the current density and make the crystals thinner. Ultra-thin copper foil is required for fine lines, especially under 5 mil, to reduce overcorrosion and side corrosion during etching. 3.2.2.2 Rolling copper foil For the thin copper foil ultra-fine line, the contact surface between the conductor and the insulating substrate is very small, how to withstand the huge difference in the coefficient of thermal expansion between the two and still maintain sufficient adhesion, completely relying on the coarsening of the copper foil surface is not enough, and the crystalline structure of high-speed copper plating foil is rough at high temperature welding is easy to cause XY Fracture is also a difficult problem to solve. Rolled copper foil in addition to fine crystal has another advantage that is very low Stress.ED copper foil stress is high, but later on the circuit board industry plated on the primary or secondary copper stress is not so high. As a result, the thin line is easily broken when the temperature changes. So rolling copper foil is a solution. For cost considerations, high-ductility of Grade 2,E-Type or Grade 2,E-Type HTE copper foil is also a choice. Most international copper foil manufacturers are committed to developing ED fine crystal products to solve this problem. 3.2.2.3 Surface treatment of copper foils A Traditional treatment After the ED copper foil is torn from the Drum, the following processing steps will continue: A. Bonding Stage- The copper is quickly plated on the Matte Side with a high current in a very short time. Its appearance is like a tumor, which is called "Nodulization" and "Nodulization". The purpose of nodulization is to increase the surface area, and its thickness is about 2000~4000A b. Thermal barrier treatments- After the completion of tumor, a layer of Brass (Gould) is plated on it Company patent, called JTC treatment), or Zinc (Zinc is a Yates company patent, called TW treatment). It is also nickel-plated and its function is to act as a heat-resistant layer. Dicy in the resin will attack the copper surface at high temperature and generate amines and water, which will cause the adhesion to fall when water is generated. The role of this layer is to prevent the above reaction, and its thickness is about 500~1000A c. After the Stabilization- heat resistant treatment, the final "Chromation" is given. Smooth surface and rough surface are taken at the same time as an anti-fouling and anti-rust effect, also called "passivation" or "antioxidant treatment". Double treatment refers to rough surface and rough surface are rough treatment, strictly speaking, the application of this method has 20 years of history, but today in order to reduce the COST of multi-layer board and more users. The traditional treatment method described above is also carried out on the smooth surface, so that it is applied to the inner substrate, which can eliminate the copper finish treatment and black/brown steps before pressing the film. A Polyclad copper foil substrate company in the United States developed a treatment method, called DST copper foil, and its treatment method has the same wonderful. This method is rough on the smooth surface, the surface is pressed on the film, the copper surface of the made substrate is rough, so it is also helpful for post-processing. Silicification treatment (Low profile) Traditional copper foil rough surface treatment of its Tooth Profile (edge) roughness (peaks and troughs), is not good for the manufacture of fine lines (affecting just etch time, resulting in over-etch), so we must try to reduce the height of the edge. The above Polyclad DST copper foil, which is treated with a smooth surface, improves this problem, and an Organic Silane Treatment, which is added to the conventional treatment, can also have this effect. It also creates a chemical bond that helps with adhesion. 3.3.3 Classification of copper foil

Copper foil is divided into two types according to IPC-CF-150,TYPE E table electroplated copper foil,TYPE W table rolled copper foil, and then divided into eight grades,class 1 to class 4 is electroplated copper foil,class 5 to class 8 is rolled copper foil. The type class and code are listed in the table

3.4PP (film Prepreg) "Prepreg" is an abbreviation of "preimpregnated", which means that glass fiber or other fiber impregnated with resin and is partially polymerized. At this time, the resin is B-stage. Prepreg is also called "Bonding sheet" 3.4.1 film production process

3.4.2 Process quality control During the manufacturing process, Gel time, Resin flow, Resin Content test, Volatile components and Dicy components must also be analyzed to ensure stable quality. 3.4.3 Storage conditions and life Most EPOXY systems are required to be stored at temperatures below 5 ° C and have a lifespan of about 3 to 6 months. After being stored beyond this period, they must be taken out and analyzed in 3.3.2 to determine whether they can be reused. Each brand prepreg can refer to the Data sheet provided by it as the basis for operation. 3.4.4 The relationship between common film types, adhesive content and Cruing thickness is shown in the table

3.4 The present and future trends of the substrate make the substrate continuously evolve two major Driving Force (Driving Force), one is Miniaturization, one is high-speed (or high-frequency). 3.4.1 Minimization such as mobile phones,PDA,PC card, car positioning and satellite communication systems. The United States is a leading country in cutting-edge technology, and the future evolution of Chip and Package as projected by the Semiconductor Industry Association - see tables (a) and (b) - shows the challenges facing substrates. 3.4.2 High Frequency From the evolution of the personal computer, it can be seen that the CPU generation is alternating faster and faster, and consumers should not be busy, of course, for the public is a good thing. However, the production of PCB is further picking. Because of the high frequency, the substrate is required to have lower Dk and Df values. Finally, the table summarizes the current and future evolution of some PCB characteristics