BGA will become the main form of assembly in the future

Market demand for electronic products is small in volume, light in weight, easy to carry. This trend is driving semiconductor industry in high density assembly will continue to seek a new method of solving the problem. Many industry experts believe that, ball grid array BGA (ball grid array) components will become high density and high I / o applications of semiconductor component design breakthrough. Their reliability is rapidly increasing, a lot of companies that BGA will become the mainstream of the future assembly form.

The BGA concept increasingly popular. The so-called BGA is refers to the components of the contact neither lead nor pin, but the connection at the bottom of the device into an array like very small (diameter of 0.8mm) tin / lead alloy ball, pitch 1.5mm (0.060 inches), accordingly to provide reliable connection. This style of components not only for the single chip connection is ideal, and the high performance multi chip module (MCM) connection is also very reliable.

Very small diameter of tin / lead alloy ball instead of lead means can be removed by the lead coplanarity and skew caused most of the problems. With the increase of the number of I / O, BGA is not simply towards more and more fine pitch, but the use of contact spacing book of slightly larger than the fine pitch device spacing.Jedec note 1.0,1.27,1.5mm. currently being launched 1.27 and 1.5mm pitch instead of 0.5 ~ 0.4 mm fine pitch devices.

These components single chip and multi chip structure. This technique can be the I / O expansion to more than 1000. Estimated that at the end of this century, the future all ASIC applications will have 50% for 200 or more than 200 i/o. use of fine pitch devices, its fine wire is easy to damage and is extremely fine accurate placement and strict lead coplanarity.

There are three types of BGA. Another advantage of BGA assembly is adapted to existing SMT assembly process and equipment, that can use existing solder paste screen printing equipment, pick and place equipment and reflow soldering equipment. Due to the BGA average wirelength than equivalent I / O assembly line length, so it has better electrical characteristics.

FR4 PCB Board Manufacturing

Epoxy glass Burkina board, based on epoxy resin as the binder, the electronic-grade glass fiber cloth as a reinforcing material based substrate. It’s bonding sheet and the inner core thin CCL is an important base of manufacturing a multilayer printed circuit board. Mechanical properties of epoxy fiberglass cloth plate, dimensional stability, impact resistance, moisture resistance than paper substrates. It's electric excellent performance, high temperature, low environmental impact by the performance itself. In the process, other than the resin fiberglass cloth panels have great advantages. Epoxy fiberglass cloth panels, the most widely used product model for FR-4.

FR-4 material is a fire code rating, represents a material specification is meant a resin material through the combustion state must be self-extinguishing, it is not a material name, but a material grade. So now FR-4 grade material is typically used in circuit boards, there are many species, but most are based on the so-called four-function (Tera-Function) plus epoxy filler (Filler) and glass fiber made composite materials. These products are mainly used for double-sided PCB, a great amount. In recent years, due to the installation techniques and electronic products PCB technology development needs, it appeared high Tg FR-4 product.

FR4 PCB medium relative dielectric constant of air is 4.2-4.7. The dielectric constant with temperature changes within the temperature range of 0-70 degrees, the maximum variation range of up to 20%. Changes in the dielectric constant of the delay will result in a 10% change in the line, the higher the temperature, the greater the delay. Dielectric constant also changes with the signal frequency, the higher the frequency the smaller the dielectric constant. 100M the following can be used to calculate plate capacitance between 4.5 and delays.

General FR4 material PCB board signal transmission speed is 180ps / inch (1inch = 1000mil = 2.54cm). Surface generally, as the case may be, generally between 140 and 170.

Dielectric constant (Dk, ε, Er) determines the electrical signal propagation velocity in the medium. It is verse between Electrical signal propagation speed and proportional to the square root of the dielectric constant. The lower the dielectric constant is, the faster the signal transmission is.

The dielectric constant is not very easy to measure or definition, it is not only the characteristics of the medium itself, but also with the test methods, test frequency, material condition before testing and test related. Dielectric constant also with temperature changes, some special materials in development will take into account the temperature factor. Humidity is also an important factor in the impact of the dielectric constant, because the dielectric constant of water is 70, very little water It will cause significant changes.


In addition to the direct impact on the dielectric constant of signal transmission speed, it is still largely determines the characteristic impedance, in different parts so characteristic impedance matching is particularly important in microwave communication.

What to pay attention to SMT patch welding

SMT patch processing is the most electronic factory will be used in the placement technology, with high assembly density, light weight and other advantages, which can meet the requirements of miniaturization of electronic.And welding is a very important part in the processing of SMT patch, we need to understand the attention of its welding in order to avoid mistakes. What we should pay attention to SMT patch welding, here Wonderful PCB will give your the answer.

1. Temperature of the soldering iron head

In SMT welding due to the different temperature of the soldering iron head, the put in Rosin block will produce different phenomena.

Therefore, we must make it in the appropriate temperature, usually in Rosin melting faster and do not smoke when the temperature is the most appropriate.

2. SMT patch welding time
SMT welding time should be as far as possible to control the precise point, the general requirements from the heating point of welding to solder melting and welding points should be completed within a few seconds. In order to avoid a long time, the welding flux on evaporate completely, eventually lose their role to help, or because the time is too short, so that the temperature of the welding point is not up to the welding temperature.

3. The amount of solder and flux

Solder and flux are indispensable materials welding, reasonable selection of the solder and flux, is an important link to ensure the welding quality. For the usage of the solder and flux to control, too much will cause the solder joint coarse even next to the circuit and take the tin short circuit, may also in the process of mobile electric soldering iron solder drop caused by other parts of the short circuit; if too small, it can't cover the solder joint, the influence of welding firmness.

In the SMT welding process, we should also need to be careful not to touch welding point, especially in the welding point of the solders have not solidified completely and can not be freely moved welding of welded device and wire, otherwise, will point welding deformation,weld phenomenon, the influence of welding effect. Learn more about What is SMT technology here

FPC flexible printed circuit board material introduction

On the composition of FPC flexible printed circuit board material

Insulating Substrate

Insulating substrate is a flexible insulating film. As the circuit board insulating carrier, flexible dielectric thin film, the heat resistance of the comprehensive survey of the material requirements, covering shape performance, thickness, mechanical properties and electrical properties. Now engineering commonly used is film of polyimide (pi: polyimide with the, the name of the commodity, Kapton), ptfe:ployterafluoroethylene polyester (pet:polyester commodity name Mylar film and PTFE film. The general film thickness selection in the range of o.0127 o.127mm (0.5 ~ 5MIL). Polyimide film, polyester film and poly tetrafluoroethylene film performance comparison.

Adhesive sheet

Bonding sheet is adhesive film and metal foil, or bond films and film coverage (film). For the thin films deposited on different substrates can be used for different types of bonding sheet, such as polyester binder film and polyimide with bonding sheet is not the same, the polyimide substrate bonding sheet with epoxy and acrylic acid. Choose bonding sheet is focused on material flow and thermal expansion coefficient. No bonding sheet polyimide copper clad laminate, resistance to chemical and electrical performance is better.

Due to the low acrylic adhesive sheet of glass transition temperature, a large amount of contamination produced in the process of drilling is easy to remove, effect of metallized hole quality, as well as other adhesive materials to be unsatisfactory place, so multilayer flex circuit layer bonding piece of common polyimide material, since cooperating with polyimide substrate, the CTE (coefficient of thermal expansion (CTE) to overcome the size instability in multi-layer flexible circuit and other properties can satisfactory.

Copper foil

Copper foil is covered with adhesive in the substrate of the conductor insulating layer, after selective etching of the formation of conductive lines. This kind of copper foil most is the rolled copper foil (pcrca copper foil) or electrolytic copper foil (electrodeposited copper foil). The ductility of the wrought rolled copper foil and bending is better than that of the electrolytic copper foil, an extension of the rolled copper foil rate is 20% ~ 45%, the extension of the electrolytic copper foil rate is 4% ~ 40%. The thickness of copper foil is the most commonly used 35um (1oz), thin 18um o.5oz or thick 70UM (2oz), even 105um (for).

Coverage
The covering layer is an insulating protective layer covering the surface of the flexible printed circuit board, which can protect the surface of the conductor and increase the strength of the substrate.

First class is dry film type (coating), polyimide materials selection, without adhesive directly and after etching for the circuit boards in a laminated way pressing. The mulching requirements in the suppression of the pre forming, exposing welding part and therefore cannot meet more fine assembly requirements.

The second category is the photoreceptor development type. Sensitization development type of the first kind is covered dry film by film machine pressed in, by developing photosensitive exposed welding parts, to solve the problem of high density assembly; the second is the liquid screen printing covering materials, commonly used a thermosetting polyimide material, and photosensitive developing type flexible circuit board special solder resist ink.

More info on FPC board

Technology of SMT in PCB industry

SMT chip that is on the PCB Based on for processing series process referred to as the PCB (printed circuit board) for printing circuit board. (source: SMT is processing series process of PCB (printedcircuitboard) in the PCB infrastructure)


SMT is (surface mount technology) (an acronym for surface mounted technology), the electronic assembly industry in one of the most popular and a technical process. Electronic circuit SMT (surface mount technology, SMT), said for surface mount or surface mounted technology. It is a no pin or short lead surface mount components (SMC / SMD, the Chinese call sheet components) installed on the printed circuit boards (printed circuit board, PCB ) surface or other surface of the substrate, welding assembly of the circuit is connected by reflow soldering or other methods.

Usually we use electronic products are by the PCB and all kinds of capacitors, resistors and other electronic components according to the design of the circuit design, so all kinds of electrical appliances need different kinds of SMT processing technology to process.

SMT basic elements: the process of solder paste printing / parts mount -->AOI optical inspection / maintenance / return / welding plate.

Some people may ask answer electronic components why to do so complicated?? this fact and the development of our electronic industry is closely related to, today, the electronic products, the pursuit of miniaturization, previously used perforation plug-in components has been unable to narrow. Electronic product function can more complete, the integrated circuit (IC) has no perforated elements, especially on a large scale, highly integrated IC, had to use surface mount components. Product batch, automatic production, the factory to with low cost and high yield, produce high quality products to meet customer needs and strengthen the development of the market competitiveness of electronic components, integrated circuit (IC) open , semiconductor materials of diverse applications. Electronic technology revolution is imperative, chasing the trend. Can imagine, in Intel, amd the CPU, image processing production process of the component manufacturer strives to 20 nanometers, the SMT surface assembly technology and development is not to the situation.

SMT processing has the advantages of high density assembly, electronic products, small size, light weight, the volume and weight of the SMD components only traditional cartridge elements about a tenth of the common SMT, electronic products smaller 40% ~ 60%, the weight is lightened. High reliability and anti vibration can. Solder joint defect rate low. High frequency characteristics. Reduce the electromagnetic and radio frequency interference. Easy to realize automation, improve production efficiency. Reduces costs by up to 30% to 50%. Save material, energy, equipment, manpower and time.

Source: What is SMT Technology

3 PCB Design Experience

1. if the PCB design of the circuit system contains the FPGA device, it is necessary to use the II quartus software to verify the distribution of the pin before drawing schematic diagram.

2. 4 layer PCB board from top to bottom is as follows: the signal level, power supply and a signal plane layer; 6 layers from top to bottom in turn: signal level, signal in electric layer, signal electric layer, power supply, signal plane layer 6 layer above the plate (advantage is: anti radiation interference), priority in their choice of electric layer wiring, walk not to open plane layer prohibited line away from the ground or power supply.

3. Multiple power system wiring, such as FPGA DSP systems do six plates, at least in general will 3.3V 1.2V at 1.8V 5v.3.3v is generally the main power supply, direct shop power supply layer, through holes easily buton global power supply network.

5V generally may is the power input, need only in a small area of the copper paving. And as far as possible (you ask me the more thick, crude more rough, the thick, the better) 1.2V and 1.8V is separated from the kernel power (if the line is connected with the way will encounter great difficulties in the face of BGA devices), layout as 1.2V and 1.8V, and let 1.2V and 1.8V connected component placement in a compact area, the use of copper skin connection.

In short, because the power network throughout the entire PCB, if the use of the way the line will be very complex and will be around a long way, the use of copper clad method is a good choice!

Chinese and foreign current situation of printed circuit board industry

Printed circuit board as an important electronic components, electronic components supporting body. Due to its important role in the field of electronic components, so it is many people to become "electronic carrier". With the development of science and technology, printed circuit board is widely used in military, communications, medical, power, automotive, industrial control, smart phone, wear and other high-tech fields.

Therefore, PCB board level of production technology has gradually become an important indicator to measure the level of a national science and technology. However, compared with the developed countries of the printed circuit board industry development status and trends, China printed circuit board industry in which stage, there is what problem, how should solve. This is this article tries to answer the question.

1 Development status of printed circuit board industry in China

At present, the global printing circuit board industry development has stepped on a relatively stable period of development, has been formed, including Hong Kong, China, Japan, Taiwan, China, South Korea, the United States, Germany and the Southeast Asian region, including seven major production centers, of which Asia accounted for 79.7% of global gross domestic product.

China due to the distribution in the industrial, manufacturing cost have the advantage, has become the world's most important printed circuit board production base, 2013 circuit board output of China has occupied more than 44.2% of global output, but individual enterprises in China market occupies a smaller share, do not have a strong ability to lead to the market.

2 Development status of global printed circuit board industry

Since the middle period of the fifties of the 20th century, the PCB technology began to widely used. At present, PCB has become the "mother" of the electronic products, its applications almost penetration in the electronics industry in each end of the field, including computer, communication, consumer electronics, industrial control, medical instruments, national defense, aerospace and other fields. Future with the development of a new generation of information technology industry, smart phones, automotive electronics, led, IPTV, digital television and other new electronic products continue to emerge, market and application of PCB products will continue to expand.

In recent years, the global PCB industry overall is steady growth in 2009 due to the impact of the global financial crisis, PCB output value has declined, 2010 with global macro economy to improve step by step, PCB industry began to recover, the annual output value of 524.68 billion U. S. dollars, more than in 2009 increased substantially 27.33%.

Related Post:

May 2016 North American PCB business growth slowed

PCB ENIG Surface Finish

ENIG is short for Electroless nickel immersion gold. It is one of the popular PCB surface finish types. ENIG is made of electroless nickel plating and a thin layer of immersion gold, protecting the nickel from oxidation.

ENIG has several advantages. Firstly, it has excellent surface planarity, particularly helpful for PCBs with large BGA packages. Secondly, oxidation resistance is very good. Besides, its usability is suitable for untreated contact surfaces such as membrane switches and contact points. ENIG also does not wet as evenly or easily as HASL.ENIG is a expensive finish, but offers the best characteristics for printed circuit boards. The process requires the most steps compared to other common finishing types. The ENIG also has its other good characteristics, such as excellent flatness for fine pitch components, robust for multiple reflow cycles, supports alternate connections, good for in-circuit testing and press fit connectors.

The Gold readily dissolves into solder and does not tarnish or oxidize. While the Nickel strengthens the PTH and increases thermal cycle life, the Nickel barrier prevents Copper dissolution during wave solder & rework.

The electroless nickel step is an auto-catalytic process, involving depositing nickel on the palladium-catalyzed copper surface. The reducing agent with nickel ions must be filled for proper concentration, temperature and pH levels, creating a consistent coating. During the immersion gold step, the gold adheres to the nickel-plated areas through molecular exchange. This protects the nickel until the soldering process. The gold thickness needs to meet certain tolerances to ensure the nickel maintains its solderability.

Immersion Gold is replacement chemistry. In other words, it attaches to the Nickel by replacing atoms of Nickel with atoms of Gold. Immersion Gold layer is to protect the Nickel surface. The recommended Gold thickness is 2-4 µin. Its primary purpose is to maintain the solderability of the Nickel surface. Nickel, as a barrier layer to Copper, can eventually diffuse to the surface of Gold and cause the same solderability issue, which just takes place at a slower rate than Copper.


Typical ENIG specifications are defined by IPC- 4552 Specification for Electroless Nickel/Immersion Gold. The Nickel thickness must be in the range of 3-6 µm. It is sufficient to prevent porosity through the base Copper.

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How to Choose PCB Material

A well PCB design is the important step on PCB board production, but PCB material is the key bridge to make a good PCB board.

How to choose PCB material is very important.

When Choosing PCB board meterial, it must meet the needs of the design and production and cost to achieve a balance between the point.

Design requirements include electrical and mechanism of these two parts. Usually in the design of very high speed PCB board (more than GHz frequency) this material issue will be more important.

For example, now commonly used FR-4 material, the frequency of a few GHz when the dielectric loss (loss dielectric) will have a great impact on the signal attenuation, may not be applicable.

On the electrical, we should pay attention to the dielectric constant (constant dielectric) and dielectric loss in the design of the frequency is applicable.

The Exclusive Knowledge of PCB Circuit Board

Specialize in, no matter what industry has its own set of professional knowledge, PCB circuit board is no exception, today we have invited to professional and technical teacher to tell a story about some PCB board professional term, will be used in the circuit board and technical personnel as below:

Material for the production of circuit boards are usually XPC, FR1, FR2, cem1, cem3 and fr4.xpc, paper core, no 94-vo fire mark;

FR1 PCB, the paper core phenolic resin copper-clad plate (not plating, tin spraying, high temperature 105 degrees Celsius);

FR2, the paper core phenolic resin copper-clad plate (not] electroplating tin spraying, high temperature 130 degrees Celsius);

Cem1, the paper core epoxy resin copper clad glass plate (glass fiber);

Cem3, paper core epoxy resin coated glass fiber board (the whole glass fiber) is generally used for the production of a single panel;

FR4 PCB, epoxy resin copper clad glass cloth (whole glass fiber) is generally used for production of double-sided and multilayer board;

Plating: tin spraying is hot air leveling;

Line: silk screen is printed on the customer requirements, the general is white;

Master above the professional and technical knowledge of the circuit board, to lay the foundation for our future.

The new iPhone circuit board will be introduced to replace the class board technology HDI

According to Taiwan media reports, Apple may be iPhone substantial revision cycle extended from the current 2 years to 3 years, rumors 2017 launched a substantial revision of the models may make major changes in appearance, the OLED display screen, may also through high performance motor to realize complex tactile vibration.

The extension of the revision cycle will have a significant impact on suppliers in Japan, Taiwan and other parts of Asia, as these companies are highly dependent on iPhone.

Wu Jian, chairman of Taiwan PCB manufacturers Huatong revealed that have large customers 2017 the annual new phones will change the class loading plate "technology, for suppliers bring new challenges, is thought to be referring to the apple.

Market had been rumors, apple is seeking can replace the existing HDI (high density circuit board) of the class loading plate "technology, in order to adapt to the smartphone adoption of SIP (system level package) trend. With the SIP is equipped with components of the increase in the number of over limit load of HDI, Apple hopes to further introduce" class load board material application.

Wu Jian says frankly, the global smart phone market size each year about 20 billion branch, is close to saturation, the future will not appear too big change, also won't have significant growth. In order to meet the needs of customers Huatong has begun to layout the load board production line, have the confidence to grasp the business opportunities.

Further Reading: Types of PCB Boards

How to survive for PCB supplier

Currently, with the fierce competition in PCB industry in China, it is gradully getting harder and harder for pcb suppliers to survive. So how to stand out in this condition?As a pcb supplier, you must know clearly what will affect a purchaser’s decision, such as shipping, operational type, price, lead time, facilities in factory, certifications and so on.

Shipping: most of the clients prefer to choose coastal suppliers s, which are more convenient and economic for shipping, that’s why there are so many trading companies and factories in shenzhen and NingBo. Besides, to cooperate with a good shipping agent is also a necessity.

Operational type: as we all konw, for trading company, they will charge extra commission based on exw factory price for their service, so it is not cost-effective to choose trading company. So for many factories with their own trading team will have advantage in price when face to a same vendor.

Price: it is always the main factor that will affect a purchaser’s decision, so your quotation must be reasonable and 100% right, otherwise you may lose a potential and valuable customer. Besides, if your customer is doubted about your quotation, you should be confident in your price and don’t be too easy to compromise. However if they doubted for 2 or more times, you should have a double check if there’s any wrong in your quotation.

Facility: I am now working in Wonderful PCB(HK) Limited, and we have many clients from all over the world come to our factory to have a visit, many of them are glad to give us orders in spot, why? The scale, the tidy environment, and professional equipment impressed them.

Certification: for some customers, they have few chance to come to China to have a visit of the factory, so they can only evaluate by certifications, among all the certifications, UL is always the most important one. What’s UL? It is the abbreviation of Underwriter Laboratories Inc., which is the most authoritative institute in America and also a non-governmental institution for safety test and authentication in the world. The UL serial number marked in HDI PCB represents that this type of PCB has been accredited with UL certification in America. Normally, the test for PCB is about flame retardancy test and it can be classified into different levels(105 degree,130degree etc.), but the UL certification won’t be distributed, but you can search it in UL website and confirm by UL number.

Above all, as a pcb supplier, if you konw all the factors clearly and try to improve youeself in these aspects, you will be the best one sooner or later.

Printed Circuit Board (PCB) Manufacturing Quality Management

We go through strict test in our manufacturing processes for a quality control. For new orders, we initially check layout by using an automated testing machine to ensure the layout does not have any problems on routing, placement, or any other layout problems. We compare the layout and the net list to PCB design limitations and the rules. Limitations have been determined for routing widths and clearances. So we must make sure there are no overlapping, untraced connecting pins, incorrect layer placements. If any error, we immediately contact the customer to solve out and confirmation. We must ensure the PCB is capable of being manufactured.

Flying Probe Test

For small quantity, we provide the Flying Probe Test. It does not need test fixtures. Using the Flying Probe test, we ensure PCB has no short or open circuits, as well as verify that the PCB nets correspond to the design. The Flying Probe test possesses few limitations on access. It can test PCBs with almost an unlimited amount of nets. In general, the Flying Probe test will catch errors. For example, the failure rate of the PCBs is generally less than one percent.

Fixture Test

Fixture Test has many small and spring loaded pogo pins that are inserted into holes on an epoxy phenolic glass cloth laminated sheet. These are lined up with tooling pins. These pins connect with the PCB test points. Every one of the pogo pins will connect to the device of the PCB that is going to be tested. Upon initiating the device-under-test via the fixture test, many separate test points will be connected for testing. This test ensures there are no shorted or opened circuits, and will also ensure the PCB nets correspond with the design nets. This test generally maintains the PCB failure rate to less than one-tenth of one percent.

Automated Optical Inspections

Automated optical inspections (AOI) provide an internal quality check of the inside layers of PCBs with multiple layers. This type of inspection performs a vision scan of the PCB surface using scanners so the entire area of the HDI PCB can be checked. The primary advantage of AOI is that it is highly reliable and accurate and a more sophisticated type of testing than visual inspection testing. For a basic board inspection, AOI can test for the following failures:


Line width out of rules specifications
Spacing errors outside of rules specifications.
Excessive amount of Cu.
Missing pads when they are required
Shorted circuit paths
Traces or pads that were partially or fully severed.
Holes that are broken out, which is usually caused by a hole that has been drilled beyond its target pad.

Materials of Flexible PCB

Each element of the flex circuit construction must be able to consistently meet the demands placed upon it for the life of the product. In addition, the material must work reliably in concert with the other elements of the flexible circuit construction to assure ease of manufacture and reliability. Following are brief descriptions of the basic elements of flex circuit construction and their functions.

The base material is the flexible polymer film which provides the foundation for the laminate. Under normal circumstances, the flex circuit base material provides most primary physical and electrical properties of the flexible circuit. In the case of adhesiveless circuit constructions, the base material provides all of the characteristic properties. While a wide range of thickness is possible, most flexible films are provided in a narrow range of relatively thin dimension from 12 µm to 125 µm (1/2 mil to 5 mils) but thinner and thicker material are possible. Thinner materials are of course more flexible and for most material, stiffness increase is proportional to the cube of thickness. Thus for example, means that if the thickness is doubled, the material becomes eight times stiffer and will only deflect 1/8 as much under the same load. There are a number of different materials used as base films including: polyester (PET), polyimide (PI), polyethylene napthalate (PEN), Polyetherimide (PEI), along with various fluropolymers (FEP) and copolymers. Polyimide films are most prevalent owing to their blend of advantageous electrical, mechanical, chemical and thermal properties.

Adhesives are used as the bonding medium for creating a laminate. When it comes to temperature resistance, the adhesive is also typically is the performance limiting element of a laminate especially when polyimide is the base material. Because of the earlier difficulties associated with polyimide adhesives, many polyimide flex circuits presently employ adhesive systems of different polymer families. However some newer thermoplastic polyimide adhesives are making important in-roads. As with the base films, adhesives come in different thickness. Thickness selection is typically a function of the application. For example, different adhesive thickness is commonly used in the creation of cover layers in order to meet the fill demands of different copper foil thickness which may be encountered.

A metal foil is most commonly used as the conductive element of a flexible laminate. The metal foil is the material from which the circuit paths are normally etched. A wide variety of metal foils of varying thickness are available from which to choose and create a flex circuit, however copper foils, serve the vast majority of all flexible circuit applications. Copper’s excellent balance of cost and physical and electrical performance attributes make it an excellent choice. There are actually many different types of copper foil. The IPC identifies eight different types of copper foil for printed circuits divided into two much broader categories, electrodeposited and wrought, each having four sub-types.) As a result, there are a number of different types of copper foil available for flex circuit applications to serve the varied purposes of different end products. With most copper foil, a thin surface treatment is commonly applied to one side of the foil to improve its adhesion to the base film. Copper foils are of two basic types: wrought (rolled) and electrodeposited and their properties are quite different. Rolled and annealed foils are the most common choice, however thinner films which are electroplated are becoming increasingly popular.

In certain non standard cases, the circuit manufacturer may be called upon to create a specialty laminate by using a specified alternative metal foil, such as a special copper alloy or other metal foil in the construction. This is accomplished by laminating the foil to a base film with or without an adhesive depending on the nature and properties of the base film.

CEM-3 CCL dimension Stability Improvment Method

This article introduce brifely to improve the dimensional stability of CEM-3CCL by adjusting the proportions of the different length of the glass fiber glass fiber paper.

A conventional fiber glass paper is  typically adhesive bonded by fiber glass material with diameter 9-10μm and length of about 13mm. This kind of fiber glass paper (CEM-3CCL), will warping deformation in the process, especially when heat.

Thermal expansion coefficient of the resin (60-90 * 10-6cm / cm.0C)  is larger than glass fiber (5 * 10-6cm / cm.0C). Conventional glass fiber paper, due to the smaller density and larger gap,  there will be fill of more plastic resin content. which caused the dimensional change inevitably large during the heat treatment when processing.

Filling the voids by the 7mm below short glass fiber to improve the density of  fiberglass paper. When the fiberglass paper glued,  the amount of resin will be reduced and the content will be uniformity. Therefore improved the dimensional stability of CEM-3CCL.

In the glass fiber paper, the short glass fiber 7mm or less, should account for more than 20%, while more than 8mm glass fiber, should account for more than 40%. If 7mm below short fiber glass less than 20% short glass fiber, glass fiber paper does not meet the requirements of density improvement, CCL dimensional stability, the effect is not obvious. If more than 8mm glass fibers of less than 40%, the tensile strength of the nonwoven fabric decreased, CEM-3the glass sheet is prone to break in the manufacturing process.

According to the requirements of Table 1, and adjust the ratio of glass fiber paper with different length of the glass fibers. Through the papermaking machine, epoxy resin as a binder, the binder content of 10% is made of glass fiber paper. Fiberglass resin content of the above-mentioned paper carried on the glue, the adhesive sheet are shown in Table 1.

Fiberglass paper with adhesive sheet as a core material, fiberglass cloth for fabric adhesive sheet having a thickness of 1.6mm CEM-3. Characteristics of the product are shown in Table 1. (author: Wendy)

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Tabal 1 CEM-3 CCL Features Comparison

Example		1	2	3
Fiber glass ratio in the paper	13mm	40	85	100
	6mm	60	15	0
Resin Content（％）		86.5	90.4	92.2
Board Feature	Thermal Expanding（*10-6）	14	24	27
	Dimension Shrinkage（％）	0.04	0.06	0.07
	warpage（mm)	0.7	1.6	1.8