King Sun PCB

PCB Manufacturing

What Is Flexible PCB material?

Flexible PCB is a kind of soft printed board material which appeared in 1970s. The base material is made of polyimide or polyester film. Flexible PCB is good reliable and excellent flexible,and its output is close to the output of rigid pcb.FPC widely used in portable communication equipment, computers, printers and other fields.

In recent years, a two layer FCCL has been developed in order to reduce the thickness of flexible printed boards, improve flexibility, heat resistance and peel resistance to meet high performance and thin PCB. It does not require adhesives, and is directly composed of flexible insulating materials and copper foil. Due to the absence of acrylic binder, the thermal expansion coefficient of the substrate in the Z direction is small, and the dielectric loss of high-speed signal transmission is small. It is the preferred material for flexible substrates in rigid flex printed boards. However, at present, the supply of the substrate is not as large as that of the three layer substrate, and the cost is also high.

The main flexible sheet has copper clad foil polyester film, copper clad polyimide film, copper clad polyimide fluorocarbon film and thin epoxy glass coated copper sheet (thin FR – 4).

Copper-clad polyester film（PET）

The mechanical properties of copper-clad polyester film are better in tensile strength, dielectric constant and insulation resistance. It also has good anti-moisture and dimensional stability after moisture absorption. Disadvantages are poor heat resistance, large size change after heating, and lead bad welding.The working temperature is lower (below 105 degrees C). PET is only used in printed transmission lines without welding and flat cables in electronic machines.

Copper-clad polyimide film（PI）

The copper clad foil polyimide film has good electrical properties, mechanical properties, flame retardancy, chemical resistance and weather resistance. The most prominent feature is high heat resistance,the glass transition temperature of Tg is higher than 220. The disadvantage is that the hygroscopicity is high, and the shrinkage rate is high and the cost is high at high temperature or after moisture absorption, Pre bake to remove moisture before PCB welding. PI is suitable for flexible printed boards for high-speed circuit microstrip or strip line signal transmission, it’s also one of the most widely used substrates in flexible substrates.

Thin epoxy glass cloth copper clad plate

Thin epoxy glass cloth copper clad laminate is a flexible substrate developed in recent years. The thin FR-4 PCB is better than the traditional FCCL in moisture resistance performance of external insulation in addition to flexural performance, Dimension stability and other comprehensive properties. At present, it has been applied to banded IC package and the cost is lower than the PI board.

The other flexible PCB are different according to the demand. In recent years, a flexible copper clad plate with special materials has been developed, such as fluorocarbon film, aromatic polyamide paper, polysulfone film and liquid crystal polymer (LCP) film.

According to the manufacturing process, these flexible substrates are divided into two layers and three layers of flexible substrates. The difference between them is that the three layer method is made by traditional process method, that is compounded by copper foil, insulating film and binder. The two layer method is made up of insulating film and copper foil. It has several different manufacturing processes, but the common feature is no binder.

Compared with the three layer flexible substrate, the two layer method has the advantages of thin thickness, light weight, better flexibility and flame retardancy, easy impedance matching and good dimensional stability.

The two layer flexible plate is more suitable for the high speed circuit with impedance matching requirements for FPC, FPC with high density wiring, and the board of COF, TBA, CSP and other devices, and the flexible parts of the rigid flex of the printed board.

In the above two kinds of materials, it can be classified into general base material, high frequency and high speed PCB base material, high frequency circuit base material, high heat resistant base material, high dimensional stability and green environment type base material, etc.

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Multilayer PCB Manufacturing

Why Need Keep PCB Clean?

When troubleshooting non-functional or poor performance circuits, engineers can run simulations or other analysis tools to consider the circuit from the schematic level. If these methods can not solve the problem, even the best engineers may be stumped and frustrated or confused. To avoid a similar dead end, I’ll introduce you to a simple but very important tip: Keep PCB clean.

The surface cleanliness of printed boards is also known as ionic contamination. Cleanliness directly affects the surface insulation resistance of PCB and longlife of PCB.

Poor cleanliness and serious pollution of the ion will cause the weldability and surface insulation resistance of PCB to decrease. In wet environment,conductors will also cause corrosion and affect the life of printed boards.

Especially for the high density wiring board with small wire and small spacing, the effect is more obvious, so it must be cleaned strictly before and after the coating of the printed board to meet the cleanliness requirements.

Cleanliness is to clean the surface of the printed board of the unprinted solder mask film by chemical extraction (usually using isopropanol water extract with a resistivity greater than 6Mg2cm). The resistivity of the extracted solution should be greater than 2MQcm, or equivalent to 156ugcm2 sodium chloride equivalent. We should pay attention to the cleaning and operation of the environment in order to prevent the second time pollution from affecting the results of the determination.

Some materials used during PCB assembly or modification can cause serious circuit functional problems if the PCB is not properly cleaned. One of the most common problems in this type of phenomenon is flux.

Flux is a chemical used to help solder components to the PCB. Unfortunately, if it is not removed after soldering, the flux will deteriorate the surface insulation resistance of the PCB, which will seriously degrade the circuit performance in the process.

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prepreg

What Is Prepreg In PCB Manufacturing

Prepreg, also known as pre impregnated material or bond sheet, it’s the main laminating material used in multilayer printed boards manufacturer. It is a type of thin sheet material made up of resins and reinforced. Reinforcement materials can be divided into glass cloth and other composite materials. Resins include epoxy resin, polyimide, cyanate ester and BT resin.

Prepreg is the solidified state of resin sheet.because the resin is an organic polymer material. In the process of production, the curing state of the resin is usually divided into three stages of A.B and C.

The A phase is a liquid resin that can flow completely at room temperature.

The B phase is partially cross linked with epoxy resin in semi curing state, and it can be restored to liquid state under heating conditions.

The C phase is all the crosslinking of the resin, which softens under heating and pressure, but can not become a liquid again. This is the final state of the transformation of prepreg sheet after the press of the multilayer printed board.

Prepreg is a pre impregnating material that solidified the resin into the B stage.

The prepreg used for laminating laminate should be the same or compatible with the thin base material used. For example, the use of the common FR4 base material should adopt the FR4 prepreg sheet, and the glass transition temperature (Tg) should be the same, which is beneficial to the process control and the quality of the product.

At present, most of the prepreg used in Multilayer PCB manufacture is glass cloth as reinforcing material. Therefore, the following will mainly discuss glass cloth reinforced prepreg.

The glass cloth reinforced prepreg sheet is a thin material made of resin bonded fabric, impregnated with resin liquid, and then prebaked to make the resin into the B stage. In order to improve the binding force between the glass cloth and the resin, a special coupling agent is applied to surface treatment on the surface of the glass cloth used in prepreg sheet after degreasing. It is usually possible to purchase prepreg directly in the market without self – preparation.

The length direction of the glass cloth is called radial, and the warp knitting yarn is called “warp”. The direction perpendicular to the warp is zonal, and the corresponding yarn is called “weft”. The number of units per warp and weft in different kinds of glass cloth is different. Therefore, prepreg types have 106, 1080, 2112, 2113, 2116, 2165, 1500, 7628 and other specifications according to the thickness of the yarn. The corresponding thickness of each glass cloth is different after lamination.

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2LPCBDESIGN

The most common Gerber file problems and solutions for PCB design

Printed circuit boards are a key element of various businesses, especially in the digital age when electronic technology is so important in many different areas. Different types of printed circuit boards also come in different types, depending on the needs of a particular company or industry, may have different materials, shapes and sizes. PCB designers continue to try to find faster, stronger, more efficient circuit board development methods.

However, all these printed circuit boards and PCB designs have one thing in common, that is, they rely on high-quality Gerber files. The Gerber file is a digital blueprint of the PCB and is the layer-by-layer input of the PCB manufacturer’s detailed manufacturing and manufacturing processes. Gerber file errors can be catastrophic to the PCB manufacturer, resulting in manufacturing errors and premature failure of the printed circuit board or failing to work at optimal levels.Avoid Gerber file issues to ensure the integrity and accuracy of these files, which is crucial to ensure that every printed circuit board is out of line with the specifications. The following are some of the most common Gerber file problems encountered by PCB manufacturers and what they can do about them.

Empty Gerber files: Believe it or not, designers can create Gerber files or “zero-byte” files without any information. No matter who reads the file, it does not know whether the file is completely irrelevant or if there is accidental deletion. The designer must check each Gerber file to ensure it contains useful information before sending it.

Missing or incomplete documents: This is almost the opposite problem. Manufacturers need to understand each of the specifications associated with the printed circuit board, from the size of the plated through holes to the size of the board. Any missing information may cause the board to be inconsistent with the required specifications. It is important to ensure that every necessary Gerber file is ready and accessible.

Bad file tags: Although not a catastrophic error, it is strongly recommended that designers name all Gerber files according to the manufacturer’s known naming conventions. In this way, the manufacturer can immediately find the Gerber files he or she needs without worrying about whether they have the correct documents.

Too Many Aperture Lists: Gerber Files Ideally there should be a list of apertures containing all the details the manufacturer needs for the tools required for each stage of production. Multiple aperture lists can be confusing, reducing manufacturing speed and potentially increasing the chance of errors. Also note that designers create aperture lists in formats other than Gerber files, which can also lead to confusion.

Composite layer design error: If the designer’s software creates a composite layer when generating a single layer design specification, it is important to combine the images to create a Gerber file for each layer to avoid errors.

Gerber file errors are the most unforgiving of all the potential problems your printed circuit board may encounter. While most PCB design errors can be avoided with more careful and focused work, Gerber file errors are the easiest mistakes to avoid. Given that the consequences of Gerber file problems can be so expensive and time consuming, you simply can’t allow them to happen. Some ways to help you avoid Gerber file problems include:

Use Gerber file viewer to check Gerber files
Print template to ensure correct specifications
Use high-definition CAD software
Follow best quality assurance practices throughout the design process

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PCB solder question-feature

10 Tips For SMT Processing

SMT is abbreviation of surface mount technology and is currently the most popular technology and process in the electronics assembly industry. Surface Mount Technology (SMT) is called surface mount or surface mount technology. It is a method of mounting a leadless or short lead surface mount component (SMC/SMD for short) on the surface of a Printed Circuit Board (PCB) or other substrate. Reflow soldering or dip soldering and other methods of solder assembly circuit assembly technology.

SMT processing

Single panel:

(1) Simultaneous solder paste placement and plug-in pads;

(2) Stick SMC/SMD;

(3) Insert TMC/TMD;

(4) Reflow soldering.

Double panel:

(1) Paste-reflow process, complete welding of double-sided chip components;

(2) Then apply solder paste on the through hole component pad on side B;

(3) Invert the PCB and insert the via hole component;

(4) Third reflow.

Ten tips for SMT Processing

  • In general, the temperature specified by SMT processing workshop is 25±3°C;
  • When solder paste is printed, the required materials and tools are solder paste, steel plate, scraper, wiping paper, dustless paper, cleaning agent, and mixing knife;
  • The commonly used Sn paste alloy composition is Sn/Pb alloy, and the alloy ratio is 63/37;
  • The main components of the solder paste are divided into two major parts of tin powder and flux.
  • The main role of flux in welding is to remove oxides, destroy the surface tension of molten tin, and prevent reoxidation.
  • The ratio of the volume of tin powder particles and Flux (flux) in the solder paste is about 1:1, and the weight ratio is about 9:1;
  • The principle of access to warehouse materials is first-in-first-out;
  • When the paste is used in Kaifeng, it must go through two important processes to warm and stir;
  • The common production methods for steel plates are: etching, laser, electroforming, etc.;
  • The full name of SMT is Surface mount (or mounting) technology, which means surface mount technology.
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PCB material-feature

PCB Material Classification and Selection

When designing a PCB to factory fabrication, how to choose PCB material?

PCB material classification:

According to different materials (the most commonly used classification method)

Paper substrate (FR-1, FR-2, FR-3)

Epoxy glass cloth substrate (FR-4, FR-5)

Composite Substrates (CEM-1, CEM-3)

HDI sheet (RCC)

Special substrates (metal substrates, ceramic substrates, thermoplastic substrates, etc.)

Divided by resin

Phenolphthalein resin board

Epoxy board

Polyester resin board

BT resin board

PI resin board

According to the flame retardant performance

Flame retardant type (UL94-VO, UL94-V1)

Non-flame retardant type (UL94-HB grade)

The principle of PCB material use

  • For general electronic products, use FR4 epoxy glass fiber substrate
  • For the use of high ambient temperature or flexible circuit boards, polyimide glass fiber substrates are used.
  • For high-frequency circuits, you need to use PTFE glass fiber substrate;
  • For electronic products with high heat dissipation requirements, metal substrates should be used.

Factors to consider when selecting PCB materials

  • Substrate with higher glass transition temperature (Tg) should be properly selected, Tg should be higher than the operating temperature of the circuit
  • Low coefficient of thermal expansion (CTE) is required. Because the thermal expansion coefficients of X, Y, and thickness directions are inconsistent, the PCB may be easily deformed, and in severe cases, the metalized holes may be broken and the components may be damaged.
  • High heat when required. General requirements PCB can have 250 °C / 50S heat resistance.
  • Good flatness is required. SMT PcB warpage requirements <00075mm/mm.
  • In terms of electrical properties, high-frequency circuits require materials with high dielectric constant and low dielectric loss. Insulation resistance, voltage strength, arc resistance must meet product requirements.

What are the normal of PCB materials?

King Sun standing FR-4 sheet specifications:

Material Type Base Laminate Thickness (+/-)
1 0.2+/-0.038mm (Copper H/H,1/1oz)
2 0.25+/-0.038mm (Copper H/H,1/1oz)
3 0.36+/-0.05mm (Copper H/H,1/1oz)
4 0.41+/-0.05mm (Copper H/H,1/1oz)
5 0.51+/-0.064mm (Copper H/H,1/1oz)
6 0.61+/-0.064mm (Copper H/H,1/1oz)
7 0.71+/-0.064mm (Copper H/H,1/1oz)
8 0.8+/-0.1mm (Copper H/H,1/1oz)
9 0.9+/-0.1mm (Copper H/H,1/1oz)
10 1.0+/-0.1mm (Copper H/H,1/1oz)
11 1.2+/-0.13mm (Copper H/H,1/1oz)
12 1.5+/-0.13mm (Copper H/H,1/1oz)

Remark:

1) The thickness of the sheet is 0.8mm or less and the thickness of the base copper is not more than 0.8mm.

2) The above sheet thickness tolerance is IPC-4101 CLASS B/L. If the design requires the use of tighter tolerance grade sheets, a “Special Material Order Notice” must be issued to the relevant department for purchase.

3) The above sheet suppliers commonly used by our company are KB (Jianyu), NANYA (South Asia), VENTEC (Tenghui) and SHENYI (shengyi), among which the six specifications of NANYA are 36”x48” , 40”x48. ”, 42”x48”, 36.5”x48.5”, 40.5”x48.5” and 42.5”x48.5”, other suppliers’ specifications are 36”x48”, 40”x48”, 42”x48”,37 “x49″, 41″x49″ and 43″x49”.

4) The base copper thickness of our company is H/HOZ and 1/1OZ. If we exceed this range, we need to issue a “special order notice” to relevant departments.

 5) FR-4 sheets with sheet thicknesses other than this range, eg 0.15 ± 0.025mm (without copper),0.1±0.018mm (without copper), 1.9±0.18mm (with copper), 2.3±0.18mm (with copper)

In the company can produce and can be purchased, but ME need to “special materials order book” to the relevant departments.

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via in pad PCB

What Is PCB Via And Types Of Filling

PCB vias are the electrical connections between layers. Vias are handled in the following ways:

PCB vias be covered:

Standard: Over-line holes must be covered, normal screen-printed solder resisted, no special plug-hole treatment;

Plug, part of the hole is not plugged, must accept the mouth of the yellow, but does not receive the ring exposed copper.

Project Document Requirements: Normal Solder Mask

PCB vias be covered and not filled

Standard: Over-line holes must be covered, normal screen-printed solder resisted, no special plug-hole treatment;

Plug, part of the hole is not plugged, must accept the mouth of the yellow, but does not receive the ring exposed copper.

Project Document Requirements: Normal Solder Mask.

PCB vias be covered in pad not covered the vias

Standard: The wire holes must be covered, the normal whole board should be silk screened, no special plug holes should be handled; some holes must be plugged, some holes should not be plugged, and the hole ring should be exposed to copper ±2mils after opening the window according to the customer’s documents.

Project Document Requirements: Normal Solder Mask

PCB vias be not covered

Standard: All the wire holes are opened for window processing; some oil holes and plug holes are allowed in the holes, but holes are not allowed.

There is ink on the ring.

Project Document Requirements: Normal Solder Mask

PCB vias partially be covered

Standard: The area must be covered with a guideline, normal screen printing and soldering, no special plugging;

Part of the hole in the area of the hole is covered and part of the hole is not plugged. The hole must be yellowed, but not

Receiver ring exposed copper.

Project Document Requirements: Normal Solder Mask.

PCB vias partially be filled

Standard: It is necessary to make a hole in the designated area wire hole; in this area, the via hole is not allowed to transmit white light (allowing green light to pass through), but part of the hole mouth must be yellowed, but the copper ring is not received. .

Project Document Requirements: filled vias film

PCB vias filling

We can produce 2 types of channel fills:

  • Through hole filling resin
  • Through-hole filling solder resist.

Through hole filling resin

Use a special machine ITC THP 30 to fill the special hole blocking resin TAIYO THP-100 DX1 heat-curing permanent hole filling material. The additional production steps required for resin via filling are performed before the 2-layer PCB production process. In the case of multiple layers, this is after pressing.

Process overview:

  • Only drill holes that need to be blocked
  • Clean: Plasma and brushing
  • Black hole
  • Apply dry resist
  • Only through hole imaging
  • Through Hole Plating (PTH)
  • Stripping resist
  • If you need to brush your teeth
  • Baking: 150°C 1 hour
  • Blocked by resin
  • Baking: 150°C 1.5 hours
  • Brush your teeth

After these steps, the normal PCB production process begins or continues: drilling other PTH holes, as well as a normal outer production process.

IPC-4761 is classified by protection type. This resin-filled Via fill process always results in “Type VII – Fill and Cap” vias.

Note: This via fill resin type is suitable for Via-in-Pad applications.

Through-hole filling solder resist

The solder paste to be filled is filled with the solder resist as the filling material. This Via Filling technology uses a drilled ALU plate to push common solder mask ink in through holes to the filler. This is a screen printing process. This is a step before the normal solder mask process.

important:

Filling is always done from the top of the board

Solder vias filled with solder mask always give a reverse solder mask pad, and dimensions are added by tool size + 0.10mm.

In other words, this type of Via Filling will always cover the solder mask at the top and bottom.

Note: This pass-through with solder mask type fillers is not suitable for use on pads.

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solder mask peeling off-feature

Embedded Packaging Apply In PCB Industry

Increased demand for high density, versatility, and miniaturization brings new challenges to packaging and substrates. Many new packaging technologies have emerged, including embedded packaging technology. Embedded packaging technology is to embed passive components such as resistors, capacitors, inductors and even active devices such as IC in printed circuit boards. This approach can shorten the length of lines between components, improve electrical characteristics, and increase the effective printed circuit board package area. Reducing the number of solder joints on the printed circuit board surface, thereby increasing the reliability of the package and reducing the cost, is an ideal high-density packaging technology.

According to Kingsun engineers, early embedded technology was mainly used on PCBs and now also on package substrates. Embedding passive devices such as resistors and capacitors in the PCB is already a very mature technology. The embedded technology is transferred from the PCB to the substrate, which is more difficult to implement because the finer substrate and thinner breakdown thickness require more manufacturing processing capability and higher precision. However, due to the same technical principle, its passive devices embedded in the substrate have also rapidly achieved mass production.

There are mainly two kinds of passive components such as embedded resistors and capacitors in the substrate. One is planar inlay, also called film-type buried, Only a few micrometers of resistance and capacitance materials are embedded in the board, and corresponding resistance or capacitance patterns are created through a series of processes such as pattern transfer and acid etching. Another method is to separate embedded resistors and capacitors such as 01005, 0201, 0402 and other ultra-thin package specifications directly through the SMT process and fill-hole interconnection process into the substrate. There is no limitation on the number of embedded components in the embedded package. The size of the package is mainly based on the area of the package. If the area is sufficient, it can be buried. Although this approach will increase the packaging cost, it may not necessarily increase the cost of the entire product, because it can save the cost of component purchases and SMT placement, and it will also improve the performance.

In addition to embedding passive components such as resistors, capacitors, and inductors, our company is actively developing embedded IC technology that directly embeds the die into the substrate to carry out board-level packaging, which is more complicated than embedding passive components. After long-term technology accumulation and innovation, the company has already produced samples of IC-embedded substrates. The next step is to jointly develop with customers and define the final products according to their needs.

The demand for high-density and miniaturized packaging continues to increase. It is expected that the market for built-in component substrates will continue to expand. The emergence of embedded technology contains the possibility of major changes in the industrial structure and industrial structure. From material factories, IC foundries, IC design companies, to printed circuit board/substrate manufacturers, packaging manufacturers, and system manufacturers, that is, upstream and downstream of the industrial chain. Collaboration is indispensable. According to industry insiders, “The development of embedded technology has had a great impact on the original device suppliers. At this time, they need to change, for example, their devices need to meet the embedded conditions. New technologies will surely break the inherent pattern. It is very important for enterprises to timely understand the changes in the market and timely transition. ”

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ENEPIG or plating gold for COB bonding PCB

ENEPIG Or Plating Gold For COB Bonding PCB

COB wire bonding is a wire bonding method in the chip production process. It is generally used to connect the internal circuit of the chip and a package pin or a gold-plated copper foil of the circuit board before packaging with a gold wire or aluminum wire.COB wire bonding is generate high frequency vibrations through ultrasound under the influence of pressure and vibration,metal surfaces to be welded rub against each other and oxide film is destroyed and plastic deformation occurs, the two pure metal surfaces come in close contact to achieve an atomic distance, resulting in a strong mechanical connection. After bonding, the chip is encapsulated with vinyl.

COB wire bonding process

1.Expanding crystal.

The expansion machine is used to evenly expand the entire LED wafer film provided by the manufacturer, so that the LED crystal grains that are closely arranged on the surface of the film are pulled apart to facilitate the thorn crystal.

2.Adhesive.

The expanded crystal expansion ring is placed on the surface of the back-glued machine where the silver paste layer has been scraped, and the silver paste is backed. Point silver paste. Suitable for bulk LED chips. Use a dispenser to spot the appropriate amount of silver paste on the PCB.

3.The expanded crystal ring prepared with the silver paste is put into the gill frame, and the LED chip is stabbed on the PCB circuit board by the operator under a microscope.

4. Put the PCB of Crystal into a thermal cycle oven and stand for a while at constant temperature. After the silver paste is cured, it shall be taken out (not for a long time, otherwise, the LED chip coating will bake yellow, ie, it will be oxidized and cause difficulties for bonding). If there is a LED chip bond, the above steps are required; if only the IC chip is bound, the above steps are cancelled.

5.Sticky chip.

Use the dispensing machine to place a suitable amount of red glue (or black glue) on the PCB’s IC board position, and then use an antistatic device (vacuum suction pen or sub) to place the bare IC chip correctly on the red or black glue.

6.Drying.

Place the sticky die in a heat-circulating oven and place it on a large flat heating plate for a while at a constant temperature. It can also be cured naturally (a long time).

7.Wire Bonding (threading).

Using an aluminum/gold wire bonder to bridge the wafer (LED die or IC chip) to the corresponding pad aluminum wire on the PCB, ie the inner lead of the COB.

8.Pretest.

Use dedicated inspection tools (different equipment for different uses of COB, simple high-precision regulated power supply) to detect the COB board and rework the failed board.

9.Dispensing.

The dispensing machine is used to place a good amount of AB rubber to the well-established LED die. The IC is encapsulated with vinyl and then packaged according to customer requirements.

10.Curing

Put the sealed PCB printed circuit board into a thermocycling oven and keep it at a constant temperature. Different drying time can be set according to the requirements.

11.After the test.

The packaged PCBs are then tested for electrical performance using dedicated inspection tools to distinguish between good and bad.

What kind of PCB surface fit for COB wire bonding?

Thick gold plating can provide excellent bonding performance, but due to the high cost of plating thick gold and poor soldering performance, many projects are hindered. In the deposition reaction of nickel-palladium-gold ENEPIG in the replacement of gold, the electroless palladium layer protects the nickel layer from excessive corrosion by the replacement gold. Excellent resistance to storage time, solder joint reliability, good wire bonding ability, low cost, etc. Gradually replaced electroplating thick gold process. Ordinary gold plating and gold layers are required to be very thick, basically 0.3 microns or more, to meet the requirements of bonding. The ENEPIG PCB can be satisfied with only 0.1 micron palladium and 0.1 micron gold.

The ENEPIG PCB process is similar to ENIG process in that a chemical palladium bath (reduced palladium) is added between chemical nickel and chemical gold. ENEPIG process: Degreasing-àMicro-etching-à Pickling-àPre-immersion-àActivated palladium-àChemical nickel (reduction)-àChemical palladium (reduction)-àChemical gold (substitution). Chemical Immersion Gold currently has many problems with black nickel, as well as diffusion after heating. The addition of a dense layer of palladium in the middle can effectively prevent the diffusion to black nickel and nickel.

Comparatively multiple carrier board used on the BGA carrier ,One side is the bonding wire, and the other side is the need for soldering. Both of the two side gold plating thickness requirements are not the same. Bonding requires a thick gold layer, approximately 0.3 microns or more, The solder only needs about 0.05 microns. The gold layer is thick and good but the solder strength is problematic, thin gold layer solder is OK but wire bonding is not OK. Therefore, the previous processes are covered with dry film, and two different gold plating specifications are required to meet the requirements. Now with the same thickness specifications on both sides of ENEPIG, it can meet bonding and meet the requirements of solder. At present, the palladium and gold film thicknesses of about 0.08 μm or more are sufficient to meet the bonding and soldering requirements.

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PCB solder question-feature

4 Things PCB Design Engineer Should Know

Design requirements for PCB：

PCB design shoud be right

This is the most basic and important requirement of PCB design. It is necessary to accurately connect the electrical schematic diagram and avoid the two simple and fatal errors of “short circuit” and “open circuit”. This basic requirement is not easy to do in manual design and PCB in simple CAD software. The general products have to be modified by more than two rounds of trial production. The CAD software with strong functions has inspection function, which can ensure the correctness of electrical connection.

PCB design should be reliability

This is the higher level of the PCB design,not all correct circuit board have good reliability. For example, unreasonable selection of PCB material, improper thickness and installation, improper layout and wiring of components, etc., may lead to PCB’s failure to work reliably, early failure even can’t continuing work. It is much easier to design a multi-layer board than a single or double side board, but it is not as reliable as a single or double sided board. From the reliability point of view, the simpler the structure, the smaller the use of the panel, the less the number of layers, the higher the reliability.

PCB design should be rationality

This is a deeper and more difficult requirement in PCB design. A printed board component, from the manufacturing, inspection, assembly and commissioning of the printed board to the assembly and commissioning of the whole machine until the use of the printed board, is closely related to the rationality of the printed board. For example, the shape of the board is not well chosen, the processing is difficult, the lead hole is too small to assemble, and it is difficult to leave the pilot. Every difficulty can lead to higher cost and longer working hours. And every cause of difficulty comes from the designer’s fault. There is no absolute rational design, only the process of rationalization. It requires the designer’s sense of responsibility and rigorous style of work, as well as the experience of summarizing and improving in practice.

PCB design shoud consider economics

This is a goal that is not hard to achieve and difficult to achieve, but must be achieved. It is not difficult to say that the board should be selected at a low price, and the size of the boards should be as small as possible. Direct welding wires should be connected, and the cheapest surface should be applied to choose the lowest price PCB manufacturer. The price of PCB manufacturing will fall, But don’t forget that these cheap choices may result in poor manufacturability and reliability and increase manufacturing costs and maintenance costs, The overall economy is not good, so it’s not easy. “Must” is the principle of market competition. Competition is merciless. A product with advanced principles and high technology may be aborted for economic reasons.

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