Vayu will grow exponentially over the next decade, to a full feature PCB manufacturing operation that is one of the most preferred PCB solution providers in India, with clients from all over the globe in a wide range of industries.
We are building our full feature PCB service with the latest equipment, efficient techniques to provide the highest quality, full feature PCB manufacturing and assembly for our clients. We hold ourselves to the highest standards of quality and efficiency and our clients coming to us from industries like military, aerospace, medical, telecommunications and education will bear testament to this fact, in the years to come.
What makes Vayu the preferred choice for full feature printed circuit board manufacturing? Variety of our offerings and the flexibility of our solutions. We can make just about any printed circuit board you can think of, from Flex PCBs to heavy copper PCBs to ceramic PCBs and more. Shape and size considerations are of no concern for us, nor is the size of your order.
We can supply you with RoHS-compliant boards, high-frequency features or high-temperature features – simply let us know what you need, and we’ll put our expert designers and fabricators to work creating boards just for you.
Vayu advantage – we have experts in every phase of PCB development. We are a start-to-finish, turnkey, full feature PCB manufacturing solution that can help you with the design, fabrication and assembly of your board, all the way through testing to packaging and shipping. When you’re working with Vayu for your printed circuit board manufacturing, you won’t be talking to three different companies to get everything done.
Our commonly used PCB materials include Standard FR4 Tg 140°C (Dielectric constant value 4.2), Tg 170°C, Tg180°C, Aluminum core (Domestic 1060), Copper Core, DuPont PI, DuPont (PI25UM), Domestic Shengyi PI, RO4003C, RO4350B, Ro3003, Ro3010, RT5880, etc.
Advanced PCB Manufacturing Options:
| Layer Count | Typical Value (mm) | Ultimate Value (mm) |
| 1-layer & 2-layer | 0.40 | 0.20 |
| 4-layer | 0.40 | 0.30 |
| 6-layer | 0.60 | 0.40 |
| 8-layer | 1.00 | 0.80 |
| 10-layer | 1.20 | 1.00 |
| 12-layer | 1.80 | 1.20 |
| 14-layer | 2.20 | 1.60 |
| 16-layer | 2.50 | 1.80 |
Clearance / Spacing
Clearance depends on your PCB finished copper weight. Note: 1oz=35μm. Below clearance are only for FR4 PCBs. For Aluminum PCBs, MCPCBs, Flex PCBs, Flex-rigid PCBs and other advanced circuit boards.
| Items | FR-4 PCBs | ||
| Finished Copper Weight | Clearance | Typical value (mil) | Ultimate value (mil) |
| 1oz | wire-to-wire wire-to-copper | 4.00 | 3.50 |
| wire-to-via | 8.00 | 6.00 | |
| wire-to-pad | 10.00 | 8.00 | |
| wire-to-text | 5.00 | 4.00 | |
| wire-to-the edge of PCB | 10.00 | 8.00 | |
| via-to-the edge of PCB pad-to-the edge of PCB | 12.00 | 10.00 | |
| 2oz | wire-to-wire wire-to-copper | 8.00 | 7.00 |
| wire-to-via | 10.00 | 9.00 | |
| wire-to-pad | 10.00 | 9.00 | |
| wire-to-text | 6.00 | 5.00 | |
| wire-to-the edge of PCB | 10.00 | 8.00 | |
| via-to-the edge of PCB pad-to-the edge of PCB | 12.00 | 10.00 | |
| 3oz | wire-to-wire wire-to-copper | 10.00 | 9.00 |
| wire-to-via | 14.00 | 13.00 | |
| wire-to-pad | 14.00 | 13.00 | |
| wire-to-text | 7.00 | 6.00 | |
| wire-to-the edge of PCB | 12.00 | 10.00 | |
| via-to-the edge of PCB pad-to-the edge of PCB | 12.00 | 10.00 | |
| 4oz | wire-to-wire wire-to-copper | 13.00 | 12.00 |
| wire-to-via | 16.00 | 15.00 | |
| wire-to-pad | 16.00 | 15.00 | |
| wire-to-text | 8.00 | 7.00 | |
| wire-to-the edge of PCB | 12.00 | 10.00 | |
| via-to-the edge of PCB pad-to-the edge of PCB | 12.00 | 10.00 | |
| 5oz | wire-to-wire wire-to-copper | 16.00 | 15.00 |
| wire-to-via | 20.00 | 19.00 | |
| wire-to-pad | 20.00 | 19.00 | |
| wire-to-text | 8.00 | 7.00 | |
| wire-to-the edge of PCB | 12.00 | 10.00 | |
| via-to-the edge of PCB pad-to-the edge of PCB | 12.00 | 10.00 | |
| 6oz | wire-to-wire wire-to-copper | 18.00 | 17.00 |
| wire-to-via | 24.00 | 23.00 | |
| wire-to-pad | 24.00 | 23.00 | |
| wire-to-text | 10.00 | 9.00 | |
| wire-to-the edge of PCB | 12.00 | 10.00 | |
| via-to-the edge of PCB pad-to-the edge of PCB | 12.00 | 10.00 | |
| Items | Typical value |
| Color | Green / White / Blue / Black / Red / Yellow |
| Solder mask thickness | 10μm – 12μm |
| Solder mask placement tolerance | ±1.5mil |
Silkscreen
| Items | Typical value |
| Character height | 30mil |
| Character width | 5mil |
Please contact us and we would be delighed to work with you.
The layer count of PCB determines its manufacturing technology difficulty and PCB manufacturing cost. PCB boards can be briefly classified into two categories: single-layer (single-sided) PCB and double-layer (double-sided) PCB. When it comes to high-end electronic products, a couple of signal layers can be added to the inside of PCB apart from surface routing due to some limitations in terms of board real estate and board design. During the manufacturing procedure, after routing for each layer has been finished with positioning and lamination completed, multiple layers of signals will be pressed into a single board that is called multilayer PCB. Therefore, a multilayer PCB refers to any piece of circuit board containing more than two layers of signals. Multilayer PCBs can be multilayer rigid PCB, multilayer flex PCB and flex-rigid multilayer PCB.
Due to the increasing use of IC (Integrated Circuit) package, interconnection lines become so dense that multi-substrate boards become necessary. In addition, some design problems, like noise, stray capacitance, crosstalk etc., are so protruding that should be solved through multilayer resolution. As a result, multilayer PCB design has to make sure that signal lines should be minimized and parallel circuits should be avoided, which is apparently difficult to be obtained in either single-sided or double-sided design. Therefore, multilayer printed circuit boards come into being for the acquisition of perfect performance of circuits.
The original aim of multilayer PCB is to provide more freedom in terms of routing for circuits that are complex and/or sensitive to noise. There are at least three layers in a multi layer circuit board and two layers are external with the left layer(s) synthesized inside insulating plate. The electrical connection in a multilayer PCB derives from plated through hole on the cross section of circuit board.
• Smaller size
• Lower weight
• Higher speed of signal transmission
• Constantly low impedance
• Better shielding effect
• Higher assembly density
| Item | Capability |
|---|---|
| Material | FR4 Tg 140C/150C FR4 High Tg 170C/180C FR4 Halogen-Free FR4 Halogen-Free & High Tg |
| Board Type | Multilayer Rigid PCB Multilayer Flex PCB Rigid-Flex Multilayer PCB |
| Layer Count | 1-32layers |
| Board Dimension | 6mm*6mm – 600mm*700mm |
| Board Thickness | 0.6mm – 3.2mm |
| Copper Weight | 0.5oz – 6oz |
| Min. Spacing/Tracing | 3mil/3mil |
| Surface Finish | HASL (lead & lead-free) ENIG Immersion Silver/Tin OSP |
| Min. Annular Ring | 3mil |
| Aspect Ratio | 10:1 |
| Min. Drilling Hole Diameter | 6mil, 4mil (laser drill) |
| Other Techniques | Blind/Buried Via Gold Fingers Press Fit Via in Pad Electrical Test |
Multilayer PCB boards can be served in so many industries including consumer electronics, medical care, aerospace, telecommunications, military, automotive, wearables, IoT etc. based on its benefits. Vayu has been striving to provide high-quality multilayer PCBs for customers with full concerns in terms of design, cost and lead time. Contact us to find reliable experts of multilayer PCB manufacturing!
The development of manufacturing technologies and evolution of fabrication process allow PCB manufacturers to print custom designed PCBs within days. While our regular turnaround time for printed circuit boards is fast and above standard for the industry, we understand that there are times when just fast isn’t fast enough. By offering PCB expedited service, we ensure you meet all deadlines (even when your schedule suddenly tightens up) and get quick turn PCBs with time to spare.
Lead time, at Vayu, refers to the time for PCB fabrication. It’s counted from the second day following order payment receipt and file confirmation (holidays and weekends are not included).
Generally speaking, our lead time depends on the PCB design’s complexity and your custom requirements. We can manufacture a large quantity of circuit boards within 30 working days. If you’re in no particular hurry to get printed circuit boards and would like to reduce costs, just choose a more generous lead time.
PCB is the most important part of electronics. Alternately, the acronym has also accounted for printed wiring boards and printed wiring cards, which are essentially the same thing. Due to the crucial role of these boards in everything from computers to calculators, PC board material selection should be undertaken with care and knowledge for electrical necessities of a given piece of equipment.
Before the development of the PCB, circuit board materials were mostly covered by nests of entangled, overlapping wires that could easily fail at certain junctures. They could also short circuit once age took hold and certain wires started to crack. As could be expected, the manual process that went into the wiring of these early boards was confusing and painstaking.
As an increasing variety of everyday electronic components began to rely on circuit boards, the race was on to develop simpler, more compact alternatives, and this led to the development of the material, PCB. With PCB materials, circuits can be routed between a host of different components. The metal that facilitates the transfer of current between the board and any attached components is known as solder, which also serves a dual purpose with its adhesive qualities.
PCB generally consists of four layers, which are heat laminated together into a single layer. The different types of PCB materials used in PCB from top to bottom includes Silkscreen, Soldermask, Copper and Substrate.
The last of those layers, substrate, is made of fiberglass and is also known as FR4, with the FR letters standing for “fire retardant.” This substrate layer provides a solid foundation for PCBs, though the thickness can vary according to the uses of a given board.
A cheaper range of boards also exist on the market that don’t utilize the same aforementioned PCB substrate materials, but instead consist of phenolics or epoxies. Due to the thermal sensitivity of these boards, they tend to lose their lamination easily. These cheaper boards are often easy to identify by the smell they give off when being soldered.
PCB second layer is copper, which is laminated onto the substrate with a mixture of heat and adhesive. The copper layer is thin, and on some boards there are two such layers – one above and one below the substrate. PCBs with only one layer of copper tend to be used for cheaper electronics devices.
The massively-used copper clad laminate (CCL) can be classified into different categories according to different classification standards including reinforcing material, used resin adhesive, flammability, CCL performance. The brief classification of CCL is shown in the following table.
| Classification Standard | Material | |
|---|---|---|
| Reinforcing Material | Paper base class | PF resin (XPC, FR1, FR2) Epoxy resin (FE-3) Polyester resin |
| Glass fiber cloth base class | Epoxy resin (FR4, FR5) | |
| Composite epoxy material (CEM) | / | |
| Lamination multilayer base class | / | |
| Special material base class | BT, PI, PPO, MS | |
| Flammability | Flame-proof type | UL94-VO, UL94-V1 |
| Non-flameproof type | UL-94-HB | |
| CCL Performance | CCL with ordinary performance | / |
| CCL with low dielectric constant | / | |
| CCL with high heat resistance | / | |
| CCL with low coefficient of thermal expansion | / | |
Above the green soldermask is the silkscreen layer, which adds letters and numerical indicators that make a PCB readable to tech programmers. This, in turn, makes it easier for electronics assemblers to place each PCB in the proper place and in the right direction on each component. The silkscreen layer is usually white, though colors such as red, yellow, gray and black are also sometimes used.
Besides knowing how PCB is layered, you should know technical terms accompanies the use of PCBs:
• Annular ring. The copper ring that surrounds the holes on a PCB.
• DRC. An acronym for design rule check. Essentially, DRC is a practice whereby the design of a PCB is checked for its functionality. Details that are checked include the width of the traces and drill holes.
• Drill hit. Used to describe all holes on a PCB, whether correct or misplaced. In some cases, a hole might be slightly incorrect due to dull drilling equipment used during the production.
• Finger. Metal exposed along the board edge that serves as connecting points between two PCBs. Fingers are most often found on old video games and memory cards.
• Mouse bits. A PCB section overly drilled to the point where it threatens the board’s structural integrity.
• Pad. An area of exposed metal on a PCB, onto which a soldered piece is generally applied.
• Panel. A large circuit board consisting of smaller boards, which are eventually separated for individual use.
• Paste stencil. A metal stencil on a board, onto which paste is placed for soldering.
• Plane. A larger section of exposed copper on a PCB, which is marked by borders but lacks a path.
• Plated through hole. A hole that goes straight through a PCB, usually for the purpose of connecting another component. The hole is plated and usually features an annular ring.
• Slot. Any hole that isn’t circular. PCBs with slots are often high priced due to the production costs of creating odd-shaped holes on a circuit board. Slots are typically not plated.
• Surface mount. A method whereby external parts are mounted directly to PCB without through holes.
• Trace. An ongoing line of copper across a PCB.
• V-score. A place where the board has been partially cut. This can render a PCB vulnerable to snapping.
• Via. A hole through which signals travel between layers. Tented versions are covered with protective soldermask, while the untented vias are used for connector attachments.
The number that precedes a layer refers to the exact number of conducting layers, be it a routing or plane layer – the two layer types. Layers tend to have the number 1, or any of the next four even numbers: 2, 4, 6, 8. Layer boards sometimes have odd numbers, but these are rare and would make hardly any difference. For example, the PCB base material in a 5 layer or 6 layer board would be virtually identical.
The two layer types have different functions. Routing layers feature tracks. Plane layers serve as power connectors and feature copper planes. Plane layers also feature islands that determine the signaling purpose of a board, be it 3.3 V or 5 V.
FR4 is code name for glass-reinforced epoxy laminated sheets. Due to its strength, as well as its ability to withstand moisture and fire, FR4 is one of the most popular ones among all the PCB material types.
Additional PCB Design Considerations: ‘
A figure such as 1.6 mm is used to indicate the thickness of a layer board. On 4 layer boards, 1.6 mm is the standard measure. Boards with greater thickness, for example, will offer more support when heavy connecting objects need to be supported.
The standard level of copper thickness on plane layers is 35 microns. Alternately, copper thickness is sometimes indicated in ounces or grams. It’s best to go for higher than normal copper thickness on boards that support a lot of applications.
Tracks aren’t meant to transfer power, but this can sometimes happen when signals don’t properly handle frequencies. If the problem isn’t kept in check, the tracks could end up losing major amounts of power. To get as much power as possible moved from one side of a track to the other, the layout of the track must account for transmission equations.
Generally, two inches is the right track distance on layer boards that consist of copper-tracked FR4 PCB material, providing that the signal time is one nanosecond. However, you must consider the effects of transmission line for high track lengths, particularly if signal integrity is crucial. The Internet is full of programs and spreadsheets that are designed to help people make proper impedance calculations for specific layer boards.
On most boards, vias are empty, and you can usually see right through them. Nonetheless, there are various circumstances under which vias can be filled. For starters, it’s necessary for the vias to be filled when it comes to forming protective barriers from dust and other impurities. Secondly, vias might be filled to boost the carrying capacity of a current, in which case conducting materials might be used. Another reason that vias might be filled is to level a board.
Vias are typically filled with ball grid array (BGA) pieces. If contact occurs between a BGA pin and an inner layer, solder could slip through the via and onto a different layer. Therefore, the vias are filled to ensure solder doesn’t leak to another layer, and the integrity of contacts are maintained as intended.
One of the more troublesome occurrences on a layer board is when a contact breaks in and out at some point along the board. The more this happens, the sooner that part of the board is liable to give out entirely. The average home electronics user will experience this problem when one of the buttons on a calculator stops working. Each button presses down on a particular part of a layer board, and when one spot gets faulty, the button that correlates to that spot cannot send its signal.
Another way contacts can be rubbed out in certain spots is when a secondary card slot is put onto a motherboard. If the card is poorly handled, one of the spots along the card could get damaged and fail to work from there on out. The best way to protect the surfaces of board that make contact with one another is with the use of a gold layer, which serves as a life-enhancing barrier. Gold can be costly, however, and its use in the tabs adds another step in the process of PCB fabrication.
PCB Soldermask:
The color that most people are familiar with when it comes to motherboards is green, the color of soldermask. Though not nearly as common, soldermask also sometimes appears in other colors, such as red or blue. Soldermask is also known by the acronym LPISM, which stands for liquid photo imageable soldermask. The purpose of soldermask is to prevent the leakage of liquid solder. In recent years, incidences of this have become more common due to a lack of soldermask. By most accounts, however, users generally prefer boards that have soldermask over boards that don’t.
Once soldermask has been applied to PCB, the PCB is subjected to molten solder. As this process occurs, exposed surfaces of copper become solderized. The whole process is known as hot air solder leveling (HASL). As SMD chips are soldered, the board is heated to the point where solder takes on a molten form and the components are put into their proper place. As the solder dries, components also become soldered. HASL usually includes lead as one of the compounds in the solder, though lead-free options also exist.
The spacing of track width is indicated by a dash. For instance, when you see the figure 6/6 mils, that would specify 6 mils as the minimum track width, as well as the minimum track spacing. Therefore, all spacings on the board in question should either meet or exceed 6 mils. For those unfamiliar, mils units are used to determine distances on PCB materials. Width and spacing are especially important when it comes to boards that are designed to handle high amounts of current.
When a PCB board is multilayered, various tracks cannot be examined visually for their accessibility. Therefore, a test is performed that places probes at the end of tracks to verify all of the signals are reachable. The test is carried out with applications of volts from one end. If these voltages are sensed from the other side, the tracks are deemed to be in working condition. While the test is not always essential on boards with only one or two layers, it’s still recommended if you truly care about quality.
Vias that connect inner and outer layers are known as blind vias. The name is results from the fact that because such vias can only be spotted from one side. Vias that connect two or more inner layers are known as buried vias, which cannot be spotted from the outside on either side. On boards that contain blind and buried vias, via filling is often used. This keeps the outside surface more secure and helps lower the possibility of solder slipping through and penetrating the inner vias.
Material Selections Affecting Cost:
PCB typically costs more when it contains features such as gold tabs, blind or buried vias, or via filling. Likewise, PCB with line / width spacing below 6 mils also tends to cost more. The reason for these higher prices is the alternate process that goes into the production of unusual PCB boards. By the same token, certain PCB production turn out to be not nearly as profitable or successful when low mils or inner vias are featured, and the higher price is set to recoup losses. Fabricators exist that produce PCB with line / width measurements as low as 3 mils, but this is generally not recommended unless it’s your only option for a particular component.
Power and Heat Impact on PCB Material Selection:
Out of all the factors that impact PCBs, two of the most intensive are power and heat. Therefore, it’s crucial to determine the thresholds for each, which can be done by assessing the thermal conductivity of a PCB. This defines how wattage power is turned into temperature through the length of the material. However, there are no established industry-wide values for thermal conductivity.
For example, Rogers Corp. carries a PCB material, RT/duroid 5880, that is often applied in EW and communications. The dielectric constant of this material is low, as it’s a composite material that contains micro–fibrous glass elements. These microfibers aim to boost strength of the fiber in the material.
Although the PCB is ideal for applications utilize high frequencies, the material’s low thermal conductivity, made it easily heat, which can be a huge drawback in heat-intensive applications.
PCB Materials and Industry Applications:
For applications in the military and the aerospace, automobile and medical industries, PCBs are manufactured in single as well as double-sided varieties, some of which are copper clad and others that use aluminum. In each of these industries, the material is used for maximum performance in specific areas. As such, PCB core materials are selected their lightweight quality in certain industries or for their ability to handle high amounts of power in others. As such, when performance aptitudes are taken into account, it’s crucial to determine which functions need to be compared with one another when selecting PCB raw materials, since material levels correlate to performance levels.
Flex and Rigid-Flex Boards:
In recent years, flex and rigid-flex boards have grown in popularity because of the options they allow for in a variety of uses. Basically, they can be bent, folded and even wrapped around objects, so they can be used to achieve applications that would never be possible with flat circuit boards. For example, a flex board might be used for a piece of equipment that would require a board to fold at an angle and still carry current from one end to the other without the need for connecting panels.
The majority of flex boards on the market consist of Kapton, a polyimide film that was originated by the DuPont Corporation. The film boasts qualities such as heat resistance, dimensional consistency and a dielectric constant of only 3.6.
Kapton comes in three Pyralux versions:
• Flame retardant (FR)
• Non-flame retardant (NFR)
• Adhesive-less / high performance (AP)
When it comes to selecting PCB board materials, quality is of utmost importance in the construction of any type of board, whether it’s intended for home electronics or industrial equipment. A component that contains a printed circuit board could be large or small, cheap or expensive, but what matters most is that the item in question offers superior performance for the full duration of its expected lifespan.
While there are several types of PCB materials that go into a given board, product reliability is ultimately what consumers and businesses are looking for in products that use circuit boards. Of course, it’s also crucial that PCB board materials are strong enough to hold together, even if a component accidentally gets dropped or knocked sideways.
On computerized equipment, for example, durable PCBs ensure hardware updates can be made without doing damage to the pre-existing PCB board materials. The same applies to electronics devices, microwaves and other household devices that rely on PCB technology to stay in working condition. Even at electronic public facilities such as ATMs, PCBs must work without fail so buttons will work and commands will be understood without delay.
Vayu offers a full range of PCB fab and assembly services. Thanks to our experience and innovative technologies, we are capable of handling different laminate materials and substrate materials including FR4, Rogers etc. that are the most popular and widely applied. Our services have been used by engineers across industrial sectors, with unique objectives when it comes to the operation and functionality of components that use PCB.
PCB panelization is one of the most essential modern tools we have when it comes to PCB manufacturing efficiency. PCB panelization can not only improve the production efficiency of PCs and reduce delivery time, but also solve many logistics problems by using PCB panels correctly, including how to manufacture smaller printed circuit boards or boards with unusual shapes. When it comes to PCB assembly, panelization allows manufacturers to reduce labor costs and more easily control the quality of the product.
Vayu Expertise in PCB Panelization
In the area of PCB panel fabrication and panel assembly, you can be confident when you choose Vayu
. With more than a decade of experience, we’ve seen it all and have the knowledge and skills to meet all your PCB panelization needs.
There are four types of PCB panelization:
• Order Panelization: Order panelization is the most popular type of panelization because you can use it in all circumstances, which means you can apply it to the most manufacturing situations. Order panelization also creates few operating difficulties and does not affect printing quality.
• Rotation Panelization: There are some situations where standard order panelization will waste more space than necessary. We can avoid this by rotating the board either 90 or 180 degrees. This type of panelization is known as rotation panelization, for obvious reasons.
• Double-Side Panelization: Another space-saving panelization innovation is double-side panelization, where we panelize both sides of the PCB on one side as a panel. Double-side panelization is suitable for mass manufacturing — it saves specimen curve material and increases SMT overall efficiency while lowering manufacturing costs.
• Combination Panelization: Also known as characteristic panelization, this is a form of panelization involving combining different types of printed circuit board. Learn more about the different kinds of panelization, their benefits and drawbacks and the best situations in which to apply them here.
What is V Scoring?
V Scoring is the creation of the V-shaped breaking lines that connect printed circuit boards so you can separate them easily, a process that further increases efficiency. When it comes to V scoring, it’s important to cut to an equal depth, one-third on top and one-third on the bottom, leaving the middle part – “the web” – connected. Not all boards are necessarily suitable for V scoring. Vayu requires panels to be at least 0.6mm thick for V scoring.
If you’re ready to enjoy all the benefits of PCB panelization, Vayu can help you get started with entirely free panel file generation. Benefit from our manufacturing experience and highly-qualified engineering team with this service.
To learn more about PCB panels, V scoring, PCB panelization methods, your panelization requirements or anything else about our PCB services, please get in touch with us.
The development of modern electronics has been increasingly pushing PCBs towards such demands as miniaturization, light weight, high speed, better functionality and reliability, and longer lifetime, which results in the popularity of multilayer PCBs. Combined by a type of semi-solid adhesive which is called “prepreg”, two or more single and/or double-sided PCBs are stacked together to generate multilayer PCBs through reliable predefined mutual connection between them. There are three or more conductive layers in one multilayer PCB with two layers outside and one layer synthesized in the insulation board. With the increase of PCB complexities and densities, it’s possible for some issues to take place such as noise, stray capacitance and cross talk when layer arrangement gets inefficient design.
Planning optimal multilayer stack-up is one of the most important elements in determining the Electromagnetic Compatibility (EMC) performance of a product. A well-designed layer stack-up can both minimize the radiation and can stop circuit from being interfered by external noise sources. Well-stacked PCB substrates can also reduce signal cross talk and impedance mismatch issues. However, an inferior stack-up may get EMI (Electromagnetic Interference) radiation rising, because reflections and ringing in the system as a result of impedance mismatch can dramatically lower products’ performance and reliability. This article then focuses on layer stack up definition, its designing rules and essential considerations.
What is Stack-up?
Stack-up refers to the arrangement of copper layers and insulating layers that make up a PCB prior to board layout design. While a layer stack-up allows you to get more circuitry on a single board through the various PCB board layers, the structure of PCB stackup design confers many other advantages:
• A PCB layer stack can help you minimize your circuit’s vulnerability to external noise as well as minimize radiation and reduce impedance and crosstalk concerns on high-speed PCB layouts.
• A good layer PCB stack-up can also help you balance your need for low-cost, efficient manufacturing methods with concerns about signal integrity issues
• The right PCB layer stack can enhance the Electromagnetic Compatibility of your design as well.
It will very often be to your benefit to pursue a stacked PCB configuration for your printed circuit board-based applications.
For multilayer PCBs, general layers include ground plane (GND plane), power plane (PWR plane), and inner signal layers. Here’s a sample of an 8-layer PCB stackup.
PCB Layer Stackup – Vayu:
In accordance with this figure, it’s obviously clear to indicate layer distribution in PCBs conforms to a symmetrical or balanced structure. Apart from layer distribution, the spacing between layers should be taken seriously as well. To meet the requirement of miniaturization, minimum trace spacing must be obtained while planning layer stack-up. The space between layers can be either core or prepreg. Multilayer boards usually consist of at least one or more cores and prepregs. Cores are made up of a copper-plated glass-reinforced epoxy laminate sheets. The thickness of core is in the range from 0.1mm to 0.3mm.
Prepreg is the common term for a reinforcing fabric which has been pre-impregnated with a resin system. This resin system (typically epoxy) already includes the proper curing agent. The main function of prepreg is to stack all layers into a whole board by high temperature. The following table shows physical and chemical attributes of main categories of Prepreg, that is, 7628, 2116 and 1080.
Actually, thickness of each type of prepreg isn’t always stable and adjustments will be made to meet specific PCB thickness demand. Some factors have to be taken into consideration when determining the count of prepreg including thickness of inner layer, product design thickness requirement or manufacturing technology requirement, features of prepreg, practical performance and the actual thickness after stack-up trial. Below image indicates a sample 4-layer PCB whose layer distribution and thickness are depicted.
In this example, as copper thickness is stable, PCB maker will adjust thickness of prepreg and core to meet thickness need. There’re 2 methods to be compatible with the adjustment mentioned above.
• Interlayer offset. Resin recession groove is used in board side design instead of choked flow pad. In regards with stack-up positioning, hot melting plus rivet plus dowel method can be used to solve stack-up offset problem.
• Stack-up measling. In the process of board arrangement, silicon pads can be added, together with the assistance of epoxy plate so that pressure will remain balanced, which can both help eliminating stack-up measles and effectively control the uniformity of board thickness.
Based on chemical and physical attributes of prepreg, you have access to estimate thickness or copper weight of final circuit board through an easy calculation.
To obtain specific thickness of prepreg, different types of prepregshave to be combined together to achieve required thickness. For example, the thickness of 0.14mm derives from combination of two sheets of 1080 prepregs while that of 0.19mm from combination of 2116 and 1080 prepregs.
Vayu’s Standard PCB Layer Stack-up:
Vayu provides multilayer circuit boards with layers in the range from 4 to 32 layers, board thickness from 0.4mm to 3.2mm, copper thickness from 18μm to 210μm (0.5oz to 6oz), inner layer copper thickness from 18μm to 70μm (0.5oz to 2oz), and minimal spacing between layers to 3mil.
Following images present Vayu’s commonly used stack-up for Standard PCB service. The actual layer stack-up will be determined by PCB material and many other elements. If you have special requirements on PCB layer stackup, please send your circuit board thickness and layer count by email. We’ll share corresponding stack-up accordingly.
Note: Our PCB Prototype Service offers limited possibilities on custom layer stackup. If your application asks for specific layer stack-up, we recommend Standard PCB Service.
A commonly-used Layer Stackup for 4-layer PCBs
A commonly-used Layer Stackup for 6-layer PCBs
A commonly-used Layer Stackup for 8-layer PCBs
A commonly-used Layer Stackup for 10-layer PCBs
A commonly-used Layer Stackup for 12-layer PCBs
Choose Vayu for Your PCB Layer Stack-Up Needs:
If you like the idea of PCB stack-up for your electronic applications, the BEST place you need to go for layer stack up is Vayu. We offers full-service turnkey solution for all things concerning PCBs. We can help you with:
• Develop your layer stackup in PCB design
• Fabricate your stack PCBs
• Create prototypes to test your designs for any possible flaws
• Do full PCB runs
With our team having over ten years of experience in the area of printed circuit boards manufacturing, you are sure that Vayu is a name you can rely on for your multi-layer PCBs and all your PCB-related needs. We excel at speed of order turnaround, quality and value to an extent that other fabricators of printed circuit boards cannot match. Our standard PCBs meet the stringent IPC2 standard of quality, and our company is fully ISO9001:2008 compliant.
Due to environmental concerns, Vayu provides PCB full services conforming to RoHS regulations that require rigorous concentration of 6 hazardous substances including Lead (Pb), Mercury (Hg), Cadmium (Cd), Hexavalent Chromium (Cr VI), Polybrominated Biphenyls (PBB) and Polybrominated Diphenyl Ethers (PBDE) in the manufacturing of electronic and electrical products. Among the 6 types of substances, lead is the most widely applied as it plays a fundamental role in electronic plating. Therefore, lead-free solutions are the optimal prescription for RoHS-compatible PCB assembly.
Generally speaking, lead free PCB manufacturing primarily comes in lead-free solder technology and lead-free components and materials.
As a lead-free PCB manufacturer, Vayu applies lead-free solder technologies including solder ball formation technology, electro plating technology, solder dipping technology and barrel plating technology, which ensures us successfully deal with problems, tin whiskers for example, that affect reliability of products and to implement lead-free surface finishes like HASL, ENIG, ImAg, etc. on bare boards (PCBs) and assembled printed circuit boards (PCBAs).
Furthermore, we select lead-free materials that can withstand high temperature as replacement of traditional solder material. Moreover, flux in lead-free solder should be much more active than the rosin flux in traditional solder
In addition, components involved in lead-free PCB assembly have to meet the requirements for lead-free compliance accounting for reliability and suitability of final products. Owing to more than 10 years’ experience in this field, we have maintained such long-term and friendly cooperation relationship between renowned component manufacturers and distributors around the world that we’ re capable of procuring high quality lead-free components for our customers filled with environmental concerns.
With the increasing trend of miniaturization of electronic products and applications of finer pitch devices, vias become extremely popular since they are an effective solution responsible for electrical connection between traces from different layers in a printed circuit board. Vias can be classified into three main types: Through-hole Vias, Blind Vias and Buried Vias, each of which implements different attributes and functions contributing to the overall optimal performance of PCBs or even electronic products.
Via-in-pad (VIP) technology basically refers to the technology by which via is placed directly beneath component contact pad, especially BGA pad with finer pitch array packages. In other words, VIP technology leads to vias plated or hidden under BGA pad, requiring PCB manufacturer should plug via with resin prior to carrying out copper plating on the via to make it invisible.
Compared with blind vias and buried vias, VIP technology features more merits:
• Fit for fine pitch BGAs;
• Leading to higher density of PCBs and promoting space saving;
• Performing better in thermal management, beneficial for heat dissipation;
• Defeating constraints of high-speed designs such as low inductance;
• Sharing a flat surface with component attachment;
• Making PCB footprints smaller and routing further and better;
Vayu Manufactures Custom PCBs with Low Via in Pad Cost:
In accordance with Vayu’s electronic PCB manufacturing capabilities and equipment, here is a table showing our requirement for vias in pad.
| Value Type | Min. Diameter | Min. Pad | Min. Solder Mask Opening | Min. Soldering Bridge |
|---|---|---|---|---|
| Standard value | 200μm | 400μm | 50μm | 100μm |
| Ultimate value | 100μm | 300μm | 50μm | 100μm |
Owing to those advantages, via in pad is widely applied in small-scale PCBs, especially those requiring limited space for BGAs and focusing on heat transferring and high-speed designs. Although blind vias and buried vias are beneficial for density improvement and PCB real estate saving, as far as heat management and high-speed design elements are concerned, via in pad is still the best choice. With cost considered, different projects lead to different cost. So if vias are involved in your project and you fail to pick up which type, reach out to us for an optimal soution.
Vayu will implement circuit boards fabrication procedures stringently conforming to IPC-compliant guidelines and regulations in order to ensure their highest reliability and best performance in our clients’ projects. Therefore, we have to cater to tight tolerances in PCB manufacturing process.
Specific tolerances for each detail of PCB printing are listed in the following tables.
| Via Type | Via Diameter | Tolerance |
|---|---|---|
| PTH (Plated Thru-hole) | ≤0.8mm | ±0.08mm |
| >0.8mm, <2.5mm | ±0.1mm | |
| >2.5mm, ≤6.3mm | ±0.15mm | |
| >6.3mm | ±0.2mm | |
| NPTH (Non-plated Thru-hole) | ≤0.8mm, >0.8mm, ≤6.3mm | ±0.05mm |
| >6.3mm | ±0.2mm | |
| Paper based PCB | ≤0.8mm | ±0.1mm |
| >0.8mm | ±0.2mm | |
| PTH slots | <10.0mm | ±0.2mm |
| ≥10.0mm | ±0.3mm | |
| NPTH slots | <10.0mm | ±0.15mm |
| ≥10.0mm | ±0.2mm |
| Dimension | Range | Tolerance |
|---|---|---|
| Board thickness (finished) | ≤1.0mm | ±0.10mm |
| ≤1.6mm, >1.0mm | ±0.14mm | |
| ≤2.0mm, >1.6mm | ±0.18mm | |
| ≤2.4mm, >2.0mm | ±0.22mm | |
| ≤3.0mm, >2.4mm | ±0.25mm | |
| >3.0mm | ±10% | |
| Lamination thickness | / | ±8% |
| Board size (finished) | / | ±0.1mm-±0.3mm |
| Item | Specific Aspect | Tolerance |
|---|---|---|
| Hole location tolerances | Drilling | ±0.18mm |
| Milling | ±0.15mm | |
| V-cut | V-cut remain thickness | ±0.1mm |
| Bevelling | Bevelling angle | ±5° |
| Edge milling | Ordinary parts | ±0.13mm-±0.4mm |
| Internal slot | ±0.20mm | |
| Card slot | ±0.15mm | |
| Countersink counterbore | Depth | ±0.20mm |
| Angle | ±5° |
Note: Tolerances listed in tables above are for illustration purposes only.
Electrical test mainly comes in circuit Continuity and Isolation test. Due to increasing density of board traces, electrical test is covering from increasingly higher difficulties so that the advent of new types of test technologies is embraced for compatibility with the development of PCB industry.
• Continuity test refers to a process to check whether resistance value between nodes within the same netlist is less than continuity threshold so as to verify disconnections that are usually called opens.
• Isolation test refers to a process to check whether resistance value between nodes of different nets is more than isolation threshold so as to verify shorts.
As the improvement of electronic technologies and increasing complexities of electronic products, gone are the days when only visual inspection is relied on since visual inspection only works relatively well for double-layer PCBs or multi-layer PCBs prior to lamination. Nowadays, with the development of vias such as blind/buried vias, it’s difficult for visual inspection to reach that far.
In Vayu, two primary electrical test methods are being applied: Bed of Nails Fixture Test and Flying Probe Test. For either method, guidelines in accordance with IPC 9252 are rigorously adhered to so that reliability of end products will be fully guaranteed.
Bed of Nails Fixture Test:
Bed of nails fixture test, also called a calm shell or universal grid, is implemented through dozens of stiff testing fixtures just like what its name is described.
Fixtures with springs are connected to each test point on each circuit board. Springs are capable of equipping each test point with pressure of 100g to 200g to ensure excellent contact of test points. Such fixtures that are arranged in a matrix manifest themselves as a bed of nails. Controlled by test software, programming should be carried out on test points and test signals, through which testers are allowed to obtain information concerning all test points. To implement this test, fixtures will be selected and assembled according to distribution and positions of test nodes or points on a board.
Flying Probe Test:
Depending on moving probes to test electrical performance of each net on a bare circuit board, flying probe tester is actually an upgrading version of bed of nails tester. With fixtures replaced by probes that can move at a high speed, the min test pitch of a flying probe tester can be as small as 0.2mm.
During testing, unit under test (UUT) is conveyed to the inside of tester through belt or other transfer systems. Probes are then fixed to make them contact with test pad and vias. In this case, a single component of UUT can be tested through connection between multiplexing system, drivers and sensors.
Flying probe test is responsible for testing of shorts, opens and component values. Furthermore, a camera is equipped on the tester to find lost components and inspect components in terms of their shape, polarity and capacitance. Therefore, it is fit for both bare PCB fabrication and electronic assembly.
Either bed of nails fixture test or flying probe test, the tested items mainly cover from opens, shorts, capacitance to resistance in a circuit on each bare board. In addition, some reports can be summarized through testing results including cross section, solderability, peel strength etc. so that ideal performance and all functions of bare boards can be totally realized in your practical projects.
Free PCB Inspection Will Be Carried Out on All PCBs Manufactured by Vayu:
As an India PCB Manufacturer, Vayu will strive for the high quality of printed circuit boards while keeping the PCB production cost-effective. 100% electrical test has to be performed on each piece of PCB boards prior to their playing a real role in customers’ projects just to guarantee the smooth implementation of optimal performance and functions, which has been a crucial link in our PCB fabrication process.