Multilayer PCB Manufacturing

Product design, system speed requirements, microprocessors, and component scaling, and increased thermal performance are driving advances in PCB technology every day. Hemeixin’s technical and production capability and aggressive technology roadmap has kept pace with these changes and provides a scalable platform for growth.

• Layers (2-64)
• HDI PCB : 9+N+9 (Anylayer)
• Glass epoxy (GF) laminate, Tg – 180ºc Epoxy (IT180A, FR370HR etc)
• Polyimide rigid pcb laminate (Alron85N, Isola P95, Isola P96, Ventec VT901 etc)
• Low loss pcb material (I-Speed material, FR408HR, Megtron4, EM-888, N4000-13EP, N4000-13, TU-863+, TU-872lk, TU-872SLK, TU-872SLK SP etc)
• High Speed Digital PCB laminate: (I-Tera MT40 / RF, Tachyon-100G, Megtron6/R-5775, TU-883, TU-883SP, IT-968, IT968SE etc)
• RF PCB, Microwave pcb laminate: (RO4450F, Rogers 4350B, RO4835, RO4003, RO4533, Taconic TLY series, TLY-5, RF35, TSM-DS3, Astra MT77, RT/Duroid 5880, RO3203, RO3003 etc)
• MCPCB (Aluminum core or Copper Plates) laminate: Thermal conductivity:2.2~7 (W/m*k)
• Special process PCB: Countersink hole pcb, Press fit pcb, Semi flex pcb, Castellated holes pcb, Cavity pcb etc)
• Special Surface PCB: Selective gold plating pcb, Hard gold pcb, Gold fingers pcb, ENEPIG plating PCB
• Hybrid pcb , Blind and Buried Vias; Filled via capability
• Back drill: Min hole size 15.7mils Depth tolerance +/-6mils

What is a multiple layer pcb PCB?

Many printed circuit boards have one or two conductive layers, being built on either a double-sided or a single-sided substrate. A multi-layer PCB is designed and manufactured using several layers of base material. Generally speaking, any board featuring at least three conductive layers is included in this category.

It is a PCB made with three or more conductive copper layers. The conductive foil appears to be various layers of a multi-sided circuit board. The different inner layers are processed in pairs (on a core) and then bonded together using prepreg as the insulating layer. The layers are then placed in such a way that both sides of the PCB can be used to mount components with additional tracking/electrical connections on the inside of the board. Vias are used as a source of the electrical connections between the different layers of a multiple layer pcb PCB.

multiple layer pcb PCBs are constructed using a ‘sandwich’ model, featuring numerous double-sided conductive layers separated by a corresponding number of insulating material sheets. These must all be bonded and laminated together under high pressures and temperatures, such that no air gaps remain and the final PCB assembly is sufficiently robust.

Multiple layer pcb PCB Design Tips

Here are some multi-layer pcb design tips that may help:

• Route adjacent signal layers in opposite directions on the printed circuit board. If you have adjacent signal layers on layers 2 & 3, then route one horizontal and the other vertical. This will help to guard against broadside crosstalk problems.
• Use power and ground plane layers. Not only will this help distribute your power and ground evenly, but it will create a microstrip structure that will help your signal integrity.
• Reduce the size of inner signal layer thru-hole pads. Check if the fabrication shop will allow smaller inner layer pads for thru-hole parts and vias. If so, the reduced pad sizes will open up more routing channels.

The demand for multiple layer pcb printed circuit boards has been on the rise. The drive for electronics to be smaller, faster, and more powerful has made the multiple layer pcb PCB much more popular. The ability to create multiple layer pcb boards opens up a world of possibilities allowing the engineer to create more densely populated circuit boards which allows miniaturization. This is a huge benefit that double sided boards are not able to offer.

The processes to manufacture multiple layer pcb printed circuit boards require specialized equipment and a significant commitment to operator training, not to mention the financial consideration. This explains why some fabricators have been slower to enter the multiple layer pcb manufacturing market than others. Hemeixin can provide the expanded capabilities to support advanced printed circuit board designs with demanding requirements including laser drilled microvias, cavity boards, heavy copper up to 30 oz., via-in-pad, microwave & RF boards, up to 40 layers and others.

6 layer pcb

Before starting a board, I think it’s important to consider the reasons one might want to use a 6-layer PCB. There are several reasons beyond simply adding more paths for signals. The most basic version of a 6-layer stackup will take the same approach as a SIG/PWR/GND/SIG stackup in a 4-layer board and just puts signal on two additional in the center of a stackup. In reality, a SIG/PWR/SIG/SIG/GND/SIG is the worst 6-layer PCB stackup from an EMC perspective, and it’s probably only appropriate for a board running at DC.

Some of the reasons I would opt for a 6-layer board over a 4-layer board include:

• You were using a 4-layer SIG+PWR/GND/GND/SIG+PWR stackup, and you need more room on the surface layer for components. Putting PWR and SIG in the inside layers gives more decoupling with a PWR/GND plane pair.
• For mixed signal boards, you can have an entire surface layer dedicated to the analog interfaces, and there will be an extra internal layer for slower digital routing.
• You’re using a high speed board that has high I/O count, and you want a good way to separate signals into different layers of the board. You can implement the same strategy as in #1.

In all these configurations, you’re only adding one additional signal layer, not two. The other layer is dedicated to a GND plane, power rails, or a full power plane. Your stackup will be the major determinant of EMC and signal integrity in your board, as well as your layout and routing strategy.

8 Layer PCB

In typical PCB designs, a single or double-layer PCB is used. Often, a double layer PCB is sufficient to handle the requirements of the project. Also, it is best to keep the PCB design simple to reduce the risks of unnecessary problems. But some circumstances call for a multilayer PCB design. Having an 8-layer PCB stackup is less common, but it’s a practice in some applications.

A multilayer PCB generally refers to a printed circuit board with 3 or more conductive layers. These conductive layers are sandwiched between prepregs and insulative core in a PCB stackup. Prepregs are raw insulated material, usually FR4 while the core has copper layers attached to it.

As electronics become smaller in size, and signals speed is getting faster, a multilayer PCB becomes a viable option. In a standard PCB layer stackup, there are at least 4 layers of copper for signal traces. This increases space on the outer layers for components.

The best way to ensure your 8 layer PCB will operate correctly is to start with a stackup and to get it qualified with your manufacturer. Different 8 layer PCB stackups are ideal for different applications, and the PCB stackup will be the biggest determinant of EMC and routing ability. However, there are some simple guidelines that can be followed to help ensure SI, PI, and EMC in your system.

10 Layer PCB

Rigid printed circuit boards are the talk of the day. These PCBs are being used in a wide range of applications, owing to the advantages that it offers. Compact design, and production of low electronic noise are the striking features of these circuit boards, which add to their increasing popularity in applications. It is always a good idea to source these PCBs from trusted, and experienced manufacturers. One such manufacturer, which you can trust is Hemeixin. We can help you design and manufacture a 10 layer FR4 rigid printed circuit board with full body gold finish.

Most of our clients prefer gold over other materials as a surface finish option because it offers operational stability, durability, and strength to the printed circuit boards. We use processes, such as electroplating, and immersion for adding gold as a surface finish. . FR4 is used as the base material for manufacturing these PCBs, owing to its beneficial features, such as resistance to fire, good mechanical strength, and an excellent electrical insulation. Thus, these FR4 rigid PCBs with full body gold surface finish are capable of delivering an exceptional performance for several years, with little or no maintenance required.

The 10 layer FR4 rigid PCBs that we manufacture have a board thickness of 1.6 mm, and a copper thickness of 1 OZ. The minimum hole size of these PCBs is 5 mil, whereas the minimum line width is 4 mil. These PCBs do not have silkscreen, but have a green solder mask. Other solder mask color options include black, white, blue, and red. The aspect ratio of these printed circuit boards is 10:1. Other material options for these printed circuit boards, include Nelco, Getek, PTFE, polyimide, CEM3, halogen-free, Rogers, and Teflon.

At Hemeixin, we have a well-equipped facility, which enables us to manufacture high-quality PCBs in different designs specifications and capabilities. The 10 layer FR4 rigid PCBs with full body gold finish are of highest industry standards.

12 Layer PCB

Our 12 layer rigid PCB is designed to be used in high stress and temperature applications. Polyimide is used as one of the main materials as it is an organic material that provides immense heat resistance. Gold is used as the surface finish material because it helps the PCB remain stable even in harsh application environments. We have added heat sink so the PCB can dissipate heat easily in high temperature applications. This PCB has the capabilities to reach thermal stresses up to 288℃ & 20 Sec. Impedance control tolerance is at +/-10%. For custom PCB designs, we provide varied surface finish options such as carbon ink, lead free HASL, immersion tin and silver, and OSP.

There are certain applications in which, the printed circuit boards may get heated up, if proper heat dissipation is not done. Using a heat sink on the PCBs help dissipate the heat generates in the application efficiently. Equipped with a heat sink, our PCBs are specially designed to suit high temperature, and high-stress applications.

As the 12 layer rigid printed circuit boards comes with a heat sink, they have the capability to reach exceptional thermal stresses up to 288 °C and 20 Sec. The best property of these PCBs is that they have an exceptional ± 10% impedance control tolerance. You can get your PCB custom designed with a variety of surface finish options to choose from, including carbon ink, lead-free HASL, immersion tin and silver, and OSP. However, we recommend using gold as a surface finish, as it will help the PCB in delivering a consistent and stable performance even in unfriendly application environments. The base material used in these PCBs is 12L, FR4, TG170.

At Hemeixin, the quality of a product delivered is of utmost importance for us. Thus, the 12 layer rigid polyimide PCBs that we manufacture are of highest industry standards. Also, we make these high-quality printed circuit boards available at most competitive, and affordable prices in the China.

16 Layer PCB

A sixteen layer PCB provides ten layers of routing and is normally used for extremely dense designs. Generally, you see 16 layer PCB’s where the routing technology used in the EDA application doesn’t have ability to route the design to completion. “If it won’t route - just keep adding layers”. Although this is a common saying it is not good practice.
If a board won’t route to completion then there may be a number of reasons. Poor placement is often the course. Open routing channels, reduce the number of crossovers in the rats nets, place vias on a 25 MIL grid to allow through routing and basically help the router as much as possible.

There is really no limit to the number of layers that can be fabricated in a multilayer PCB(please check the capabilities of your fabricator first though). Of course, the board thickness increases as the layer count goes up to accommodate the minimum thickness of materials used. Also the aspect ratio (board thickness to smallest hole diameter) has to be considered.
Generally this is 10:1 for boards thicker then 100MIL. For example, a 200 MIL thick substrate has a minimum hole size of 20 MIL.

• When the outer layers have GND and PWR stack ups, these boards should be used for short trace runs or fan outs only. The second layer is the signal layer for the purpose of HDI. These should run traces from fine pitch ball grid arrays. For HDI uses, a producer accesses the second layer through controlled depth drilling by utilizing a laser drill.
• To get rid of or minimize warp-age, it is best to maintain the thickness of the laminate from the centerline of the PCB to between the layers. The laminate type and thickness must be set before doing the layout by CAD.
• To insure a control of impedance, it is very important to analyze the stack up with the board producer for determining copper weights, prepreg and core thickness before the board is laid out using CAD.
• Stackup layers 2 through 16 should use 1.6 mm FR 4 material. Stack ups 10 through 20 layers should use 1.8 mm FR4 material. Stackup layers 10-32 should use 2.3 mm FR4 material.
• The most common thicknesses for printed circuit boards are:

     0.8mm (0.031”) D. 1.8mm (0.070”)
     1.0mm (0.040”) E. 2.3mm (0.090”)
     1.6mm (0.062”) F. 3.2mm (0.125”)

High Layer Count PCB

High layer count PCBs, widely found in file servers, data storage, GPS technology, satellite systems, weather analysis and medical equipment are usually ≥12L with special performance requirement raw material.

Hemeixin offers a full range of rigid board constructions. It excels at high layer count / high technology boards.

MLBs with more than 64 layers, SBU with up to 9 sequential layers, stacked or staggered microvias, copper or resin filling, thick copper, embedded passives, thermal management and low CTE solutions, etc. are among our specialties.

LDI (laser direct imaging) is used for all our products.

Hemeixin has continually invested not only in the equipment and processes to allow the production of these high technology boards, but also in the latest test and inspection equipment to ensure the highest quality.

The company has also gone a stage further and invested in additional equipment such as resin fill, copper fill, Interconnect Stress Testing and a Scanning Electon Microscope to ensure maximum reliability.

With the shrinking component footprints and increasing component densities demanded by today's technology, sequential build-ups are often the only solution for the PCB construction.

Hemeixin have many years experience of producing these types of construction, incorporating buried, blind and micro vias in a range of sub-assembly combinations.

We have also invested in both copper fill and resin processes, and these combined with our in-house IST testing ensure that the reliability of these constructions meets the demands of lead-free assembly and of our military and reliability dependent customers.

High Layer Count PCB features are:

• FR4 / Polyimide / High Speed / Special Materials
• Micro via / Blind via / Buried via
• Stacked vias
• Thermal management
• CTE management
• Controlled Impedance
• Standard micro via
• Copper filled micro via
• Stacked micro via (9 layers +)
• Resin filled buried and through vias
• Resin filled and copper capped buried and through vias
• Controlled expansion
• Thermal management
• Buried resistance
• Buried capacitance
• Embedded active component technology

What is High Speed PCB Design?

In the modern world, complexity of electronic products has increased due to the demand for higher performance such as faster data transfers, better image processing, higher computing power, and greater functionality. This has resulted in higher component count in PCBs, higher signal frequencies of the order of 5GHz and more, high-speed interfaces such as HDMI, DDR-3/4, Gigabit ethernet, and HDI (High Density Interconnect) PCB technologies having blind and buried microvias. In the future, the demand for even higher performance from computers, mobiles, and communication devices would require PCBs to be designed to cope with even higher speed of operation and higher component densities.

Most PCBs can be considered to be at risk of some type of signal integrity problem that is normally associated with high speed digital design. High speed PCB design and layout focuses on creating circuit board designs that are less susceptible to signal integrity, power integrity, and EMI/EMC problems. While no design is ever totally free of these problems, by following these high speed board design guidelines they can be reduced to the point where they are unnoticeable and do not create performance problems in the final product.

High Speed PCB Design Considerations

There are special considerations one needs to take when designing a high-speed PCB:

1. All high-speed interconnections need to be designed as transmission lines and not just as point to point interconnections to reduce signal distortion, crosstalk and electromagnetic radiation.
2. All causes of signal degradations need to be kept under control within acceptable limits.
3. Adequate PCB technology is to be chosen so as to meet the demands of component density, wiring density, communication protocols, and complex devices.
4. All causes of unacceptable levels of electromagnetic radiation need to be kept under control.
5. Adequate power integrity has to be maintained in spite of high-frequency noise on power and ground rails in high-speed circuits – ensuring adequate power supply voltages are maintained at all the electronic devices and components for them to function properly.
6. Adequate and special PCB routing schemes need to be adopted to meet the demands of component density, wiring density, communication protocols, and complex devices.

The first three of the above points are usually covered under the disciplines called Signal Integrity and PCB stackup design, the fourth point is covered under the discipline called EMI, the fifth is covered under Power Integrity, and the sixth under Special layout routing techniques.

We will now discuss these in requisite details in the following sections.

How to Control the Impedance?

The factors that influence impedance are the PCB materials dielectric, the trace thickness, width and height from the ground plane.

The designer should make sure that the manufacturer has the ability to provide the right pattern size, position, and tolerance. The board might turn out to be useless if these parameters aren’t achieved.

The two types of commonly implemented impedance controls are:

Controlled dielectric thickness:

The designer provides the controlled dielectric stack-up to the manufacturer. Since impedance traces are not specified here, the manufacturing focus is completely upon building a board within +/- 10% tolerance of the specified dielectric thickness from layer to layer.

Impedance control:

Here the impedance is controlled through the dielectric thickness, the trace width, and space. The manufacturer performs a test to ensure that the desired impedance can be achieved using TDR coupons. Some adjustments are made depending upon results from the first articles in order to meet the designer’s needs and the boards are manufactured within the specified tolerance.

High speed PCB Stackup Design

High-speed designs demand critical signal integrity requirements and crafting a PCB with the right stack-up becomes part of the overall signal integrity equation. The selection of the PCB materials for impedance, dissipation, and other signal characteristics along with the right order and number of layers of the materials, need to be considered.

A stack-up, also known as build-up, is the construction of a multilayer PCB in a sequential order. Almost 99% of the time, the stack-ups will be symmetrical. The stack-ups are made up of cores, prepregs and copper foils. The majority of the products fall under 62-mil board thickness.

The PCB construction depends on the component packages used in the design, required signal trace density, and impedance matching requirements. For the high-speed PCBs, using a multilayer PCB with buried ground and power supply planes is mandatory. Solid copper planes allow designers to keep the device ground and power connections short. Further, the ground plane offers low inductance return paths for the high-speed signals.

Planning High Speed PCB Stackup

An accurately stacked PCB substrate will effectively reduce electromagnetic emissions, crosstalk, and improve the signal integrity of the product. A poorly arranged stack-up might increase EMI emissions, crosstalk and also the device becomes more susceptible to external noise. These issues can cause faulty operation due to timing glitches and interference which dramatically reduces the performance of the product.

With the right stack-up, the designer can suppress the noise at the source rather than correcting the issues after the product is built. PCBs involving multiple planes enable signals to be routed in microstrip or stripline controlled impedance transmission line configurations. The signals are tightly coupled to the ground or power planes and improve signal integrity by reducing crosstalk.

In high-speed PCBs, the ground and power planes perform three significant functions:

• Controls crosstalk amongst signals
• Deliver stable reference voltages for exchanging digital signals
• Distribute power supply to all the logic devices

While choosing a multilayer stack-up the designer should consider the following:

• A signal layer should always be placed right next to a plane.
• The signal layers should be tightly coupled (<10 MIL) to their adjacent planes.
• A power plane or a ground plane can be incorporated for the return path of a signal.
• Determine the return path of the signals. The high-frequency signals take the path of least inductance.

Selecting High-Speed PCB Materials

The most common PCB material is FR4. This material is used in most electronic applications. However, when it comes to high-frequency signals, especially in the microwave domain, FR4 is not suitable.

When designing PCB circuits at microwave frequencies, the key characteristics that define circuit laminate performance for microwave/RF printed-circuit boards include:

• Dielectric constant(Dk)
• Dissipation factor (Df)
• Coefficient of thermal expansion (CTE)
• Thermal coefficient of dielectric constant (TCDk)
• Thermal conductivity

The high-frequency material perhaps most familiar to users of PCB laminates is polytetrafluoroethylene (PTFE) which is a synthetic thermoplastic fluoropolymer that has excellent dielectric properties at microwave frequencies. Rogers materials are also commonly used.

High-Speed PCB Routing, Signal Integrity, and Power Integrity

Signal integrity starts with designing to a specific impedance value in your board and maintaining that during layout and routing. Some other strategies to ensure signal integrity include:

• Aim for shorter routes between components to ensure high speed signals
• Try to minimize routing through vias, ideally only using two vias into and out of an internal layer
• Eliminate stubs on ultra-high speed lines (e.g., 10G+ Ethernet) with backdrilling
• Pay attention to the need for any termination resistors to prevent signal reflection; look at datasheets to see if on-die termination is present
• Consult with your fabricator on which materials and processes can help you avoid fiber weave effects
• Use a rough crosstalk calculation or simulation to determine appropriate spacing between nets in your circuit board layout
• Keep a list of the buses and nets that require length matching so that tuning structures can be applied to eliminate skew

These important points can be encoded as design rules for your routing tools, which will help ensure you comply with best practices on high speed design.

High Speed PCB Routing

The design rules you set in your high speed design project will ensure you meet impedance, spacing, and length targets as you route your design. In addition, important rules in differential pair routing can be enforced in your routing, specifically minimized length mismatches to prevent skew and enforced spacing between traces to ensure differential impedance targets are met. The best routing tools will allow you to encode your trace geometry limits as design rules so you can ensure performance.

One of the most important points in high speed PCB routing is placement of ground planes near your traces. The layer stack should be constructed to have ground planes in layers adjacent to impedance controlled signals so that consistent impedance is maintained and that a clear return path is defined in the PCB layout. Traces should not be routed over gaps or splits in ground planes in order to avoid an impedance discontinuity that creates an EMI problem. Ground plane placement isn’t limited to ensuring signal integrity, it also plays a role in power integrity and ensuring stable power delivery.

Power Integrity

Ensuring stable power delivery to high speed components is critical in PCB design as power integrity problems often masquerade as signal integrity problems. They also create unnecessary radiation from interconnects and buses as transients create strong oscillations that radiate strongly. To ensure stable power delivery, use decoupling capacitor groups with a range of self-resonances to ensure the design will have low impedance over the broadest possible bandwidth. Using a power and ground plane pair on adjacent layers provides additional capacitance to help keep PDN impedance low.

High Temperature PCB Manufacturing

WHERE DOES THE HEAT COME FROM IN A PCB HIGH-TEMPERATURE SITUATION?

Another reason why high-temperature laminates are so important when working with PCBs is that potentially damaging heat can come from almost anywhere, with unpredictable effects. If you assume heat will not be a problem for your PCBs, you may be in for a rude awakening. If you’re not clear on exactly where your potentially damaging heat effects may be coming from, some possible heat sources include:

• Heat created by a component mounted to the circuit board, such as gallium nitride transistors added to boost power levels of RF/microwave systems.
• Heat generated by an element external to the circuit board — for example, in automotive electronic systems.
• Heat built up due to use of the circuit board in an improperly ventilated environment.

Rather than try to anticipate where heat sources will come from, if there is any chance you will be using your PCB in a high-temperature environment, you want to make sure you are using circuit materials designed to resist the effects of high temperature, including high-temperature laminates.

High Temperature Polyimide PCB Material

The most common high temperature polyimide materials include:

• ARLON： ARLON 85N
• VENTEC: VT-901
• ISOLA： P95
• ISOLA： P96

High Temperature Polyimide PCB Processes

Hemeixin custom manufactured many double-sided, high-temperature printed circuit boards (PCBs) for a client from the Telecom/IT Industry. These PCBs are capable of withstanding continuous operating temperatures of 250° Celsius.

Some of the processes used to manufacture these boards included:

• Shearing all raw material to size
• Drilling all necessary holes
• Copper plating
• Chemical etching to remove excess copper material
• Primary imaging

In addition to these processes, hot air solder leveling was also performed, adding an extra layer of protective metal over the copper surface. Holding tolerances as close as ±.005″, the finished PCBs were constructed from polyimide laminate and measured 10.5″x 3″. Meeting stringent industry standards and client specifications, we delivered all finished units to our consumer’s facility in Worldwide. The units fulfilled our customer’s high expectations for both quality and high temperature reliability.

High Density Interconnect PCB, with microvia≤0.15mm， use fine feature technology to connect components in small packages. HDI’s smaller geometry allows for higher wiring density. The electrical performance is greatly improved because of control on lower parasitic, minimal stubs, removal of decoupling capacitors and lower crosstalk. RFI and EMI is much lower due to ground planes being closer together, distributed capacitance is closer.

Many electronic applications are seeing a need for increasingly faster frequencies. As frequency increases, the margin for error and/or deviations in the pcb is significantly reduced. The use of high frequency material like PTFE substrates, blind vias and tightly controlled etch tolerances are required to achieve such high frequencies.

High layer count PCBs, widely found in file servers, data storage, GPS technology, satellite systems, weather analysis and medical equipment are usually ≥12L with special performance requirement raw material.  

Metal Core PCB Manufacturing

MCPCB, A metal-based PCB, is comprised of a metal substrate (ie Aluminum, Copper or Stainless Steel ect.,), thermal dissipating dielectric and the copper circuit. Due to its superior heat dissipation, MPCBs are used for a wide array of applications. You can find them in power supplies, LED lighting or anywhere that heat is a major factor.

The conventional PCBs have electrical connection on the normal FR-4 material through the vias. After a long-term development, it has evolved from single-layer to double-layer, multi-layer PCBs.

Countersink Holes PCB Manufacturing

What information is required to fabricate a countersink holes pcb?

Countersinks most commonly will have either an 82 degree or 90 degree angle so a primary consideration is the desired angle. Additionally, you would need to specify the diameter of the smaller hole, and either the maximum diameter or the depth of the countersink. And, whether that hole is to be plated or non-plated. In most cases, these are non-plated but there could be situations where you may be grounding to a chassis and would need to have plating in the hole.

Selective Gold Plating PCB Manufacturing

Why build selective gold plating pcb?

The hard gold finish basically offers tough resistance to friction compared to other finishes. It is used to create gold fingers on circuit boards. This finish is the best option when a PCB is designed to be inserted into another board, such as RAM. Hard gold is extremely durable, thus can withstand repeated usage. This finish is expensive and has poor solderability, hence, it is not applied on solderable surfaces.

For any areas on a circuit board that will require wire bonding or touch pads, ENIG is often a good choice. Organic solderability preservative (OSP) is good match for the ENIG finish, as it is lower in cost and will not harm the gold. The process of combining OSP and ENIG is referred to as “SENIG” or selective ENIG. The problem with using the ENIG and OSP process for manufacturing is the potential corrosion of the nickel used in the product. The nickel used must be highly resistant to corrosion, as the processing of the OSP finish leaves it vulnerable.

Whenever there is a requirement to plate specific areas on the board with hard gold, you can opt for selective gold plating. The process of selective gold plating is a bit different. For this reason, it is necessary to specify your requirements while raising a quotation.

Press-Fit Holes PCB Manufacturing

What are Press-Fit Holes?

Press-fit holes are plated through holes with tighter tolerances than the standard +/-0.10mm. Press-fit holes fit the leads of connectors that will not be soldered but pressed into the holes. To accommodate lead and hole to tightly fit together, the tolerances are well defined and more tight than standard.

The typical tolerances for the PTH depends on the type of connector, which is specified by the connector manufacturer.

Therefore it is of utmost importance that these tolerances are well defined in your PCB data and that the parameter “Press fit” is checked in the order details.

SEMI FLEX PCB Manufacturing

Why use SEMI FLEX PCB ?

SEMI-FLEX is flex to install. Unlike polyamide, the FR4 core is not capable of continuous flexing.

With simple depth-milling a standard printed circuit board can be prepared for flexible installations.  So called "semi-flexible" printed circuits are offering a cost-efficient solution. They save connectors and increase reliability while decreasing size of the application and time needed for assembly. Semi-flexible PCBs are the perfect solution if you have flex-to-install requirements only and there is no dynamic bending during operation.

Production of a semi-flexible PCB is identical with the manufacturing process of standard printed circuits. Semi-flexilbe boards can be produced as single-layer, double-layer or multilayer PCBs. With the exemption of a special solder mask that sustains bending, the materials are also identical to standard printed circuits. The only difference happens at the end of the production process when dedicated bending areas are milled down by z-axis routing. The remaining material can be bend and is thin enough to only carry the copper traces and little base material.

However it will bend a limited number of times at a controlled radius and to any angle.

This makes it an ideal solution where you need to mount two PCB’s in a unit at an angle to each other. Instead of using connectors and cables or a composite flex-rigid PCB, you can design a single FR4 SEMI-FLEX PCB which can be safely bent a sufficient number of times to allow installation and subsequent maintenance as needed.

Hard Gold PCB Manufacturing

Why hard gold pcb?

For the Hard Gold Plating, the entire panel is covered by tape. Only the part that requires the application of a surface finish is removed. Unlike ENIG, in this case, the copper thickness can vary by controlling the duration of the plating cycle. The nickel is first electrodeposited, then the gold is deposited according to the customer's request. The gold thickness provides an excellent shelf life but also one of the most expensive surfaces finishing options. To sum things up, Hard Gold Plating surface finish has mechanical properties, excellent shelf life and provides a flat surface. There are also drawbacks such as high cost, poor solderability and the process is complex.

Often a PCB is used in combination with a membrane switch where the underlying gold must withstand many actuation forces of a keypad.  The gold plating on tabs of a keypad is usually defined by the engineer at 200-300 micro inches. Hard gold is meant to survive many actuation forces or insertion and removal up to 1,000 actuations or more.

To better understand the longevity, think of your keyboard or calculator. Each depression to make a contact must hold up to long usage. This type of gold plating is electroplated or electrolytic plated by using an electrical charge as opposed to a purely chemical reaction. Thickness may be controlled by varying the plating cycle time. Thickness is usually between .000015”-.000050” standard processing.

Flash electrolytic is a thin coating of hard gold. Unlike thicker hard gold coatings, flash gold remains solderable for SMT assembly because its coating thickness is approximately 10% as thick as hard tab gold. Like ENIG, its thickness range is limited – typically .0000015”-.000003” thick.

Gold Fingers PCB Manufacturing

How to choose surface finish for gold fingers pcb?

Hemeixinpcb offers two types of gold finish: Electroless Nickel Immersion Gold (ENIG) as a surface finish for the whole PCB, and hard plated gold over plated nickel for edge-connector fingers. Electroless gold gives excellent solderability, but the chemical deposition process means that it is too soft and too thin to withstand repeated abrasion. Electroplated gold is thicker and harder making it ideal for edge-connector contacts for PCBs which will be repeatedly plugged in and removed.

Hard gold finish, also known as electrolytic hard gold, is made of a layer of gold with hardeners that will maximize durability. Using an electrolytic process, it is plated over a nickel barrier coating. The thickness of this plating varies according to the duration of the plating cycle.

The plating procedure uses gold because gold has high corrosion resistance, high electrical conductivity, and can be alloyed with cobalt or nickel to develop resistance to wear and tear. Gold plating can range in thickness from 3µ” to 50µ”.

Castellated Holes PCB Manufacturing

Why are castellated hole?

A popular trend among manufacturers is board-to-board soldering. This technique allows companies to produce integrated modules (often containing dozens of parts) on a single board that can be built into another assembly during production. One easy way to produce a PCB that is destined to be mounted to another PCB is to create castellated mounting holes. These are also known as "castellated vias" or "castellations."

Plated half-holes (or castellated holes) are predominantly used for board-on-board connections, mostly where two printed circuit boards with different technologies are combined. E.g. the combination of complex microcontroler modules with common, individually designed PCBs.

The board-on-board PCBs therefore need plated half-holes, which serve as SMD connection pads. Through directly connecting the PCBs together, the whole system is considerably thinner than a comparable connection with multi-pin connectors.

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