Tag Archives: PC Board fabrication

Circuit Board Fabrication of Metal Core PCB’s

Circuit Board Fabrication of Metal Core PCB’s

The circuits boards composed of metallic cores is known as a metals PCB’s, and it is commonly utilized in LED devices. Metal Core PCB is harder to manufacture than FR-4 and can be more costly. Metal Core PCB (MCPCB) or Insulated Metal Substrate (IMS PCB) would be a technique created to address the FR4 substance’s thermodynamic constraints. If your boards must operate in a high-temperature condition, Metallic Core is a stronger option than FR4. Insulation Metal Substrate uses a unique insulator with a higher thermally conductance to offer electrically isolated among the copper and the metals cores.

Metal Core PCB Manufacturing is the process of designing and fabricating printed circuit boards (PCBs) with a metals core to be used with LED-based Solid States Illumination as well as other technologies that requires energy dispersion. Because adaptive elements could cause hotspots on an FR4 Printed Circuit Board, another type of cooling is required to ensure acceptable working conditions. Thermal vias underlying heat-generating elements (energy sources) can be used to transmit heat from the element (upper surface) to the base PCB layer, where it could be dissipated by a heat sink.

Manufacturing of Metal Core PCBs

Metal Core PCB Manufacturing offers a slew of advantages for a wide range of purposes. Because MCPCBs feature dielectric polymers layers as well as higher thermally conductance levels, they could attain a low heat resistance. Metal Core PCB Manufacture results in a solution that can transmit heat 9 times faster than a standard FR4 PCB. The laminates of MCPCBs disperse heat, ensuring that heat-generating aspects stay cooler. As a result, such elements have a longer working life and better efficiency.

The metal cores must first be drilled to enable layers transitions avoiding causing a short circuit in multilayered dielectric stacks. To begin, slightly larger holes are drilled into the metallic surface, which are then filled with insulation gel. The gel will be cured and solidified, allowing it to be plated with copper in the same way as a normal via can. The remainder of the stack is compressed and joined to the metallic surface, and then through-holes are machined in the stack up, which is then plated and cleaned.

Due to the existence of a metallic surface in the stack-up, metal-core PCBs should follow a specific method. If the circuit is a single-layer board with no layers transitioning back to a metal frame, the normal FR4 Circuit board fabrication procedure of pressing and bonding the insulating surface to the metal cores could be employed.

Purposes of Manufacturing of Metal Core PCBs

Metal Core PCB Manufacturing has a plethora of new uses as a result of the acceptance of new technology. This technique is effective for situations in which elements create a lot of heat and can’t be chilled utilizing traditional fans or other cooling techniques. MCPCBs are used in Solid States Lighting to assist achieve a higher level of luminosity with few LEDs.

Despite the numerous benefits of LED-based Solid State Lighting technology, they emit considerable quantities of heat. As a result, Metal Core PCB Manufacturing is beneficial for purposes such as:
● Automobiles Lights Fixtures in Basic
● Converters of energy (mechanical, telecom, energy accumulations, and great charge controls)
● Photovoltaic
● Security on the Street (brightness, streetlights, etc.)

Advantages of Metal Core Printed Circuits Boards

Metal cores PCBs have several capabilities over ordinary core components, including the capability to use a dielectric polymer with a high thermally conductance for decreased thermally impedance. A metal core PC Board can transport sound up to 9 times quicker than a normal FR4 lamination. The core materials used by MCPBC are great at dissipating heat and preserving essential heat-generating equipment cold, which can improve effectiveness, productivity, and lifespan. Benefits of Backlighting, the insulating impact of an iron core metal PCB, the brittle ceramic substance is replaced, suitable for putting on the wall, decreases labor and operational costs, and enhances product high thermal stability and structural qualities by replacing elements such as the heat sink all are the benefits of using Metal Core Printed Circuits Boards.

Whenever the energy from an LED was never adequately dissipated, problems happen; an LED’s lighting production is diminished, as well as degeneration when the heating stays stagnant in the LED packages. The goal of an MCPCB would be to effectively evacuate energy from across all current integrated circuits (not just LEDs). Among the ICs and the heating element, the aluminum bottom and thermal conducting insulating layers operate as bridging. Numerous heat sinks on top of surface-mounted equipment are eliminated since one singular heat sink was installed immediately to the metal foundation.

The fundamental feature of the materials is thermally expansions and contracting; nevertheless, various CTEs have varying thermal expansions. Aluminum and copper offer distinct advantages over standard FR4 in terms of thermal conductance, which can be as high as 0.83.0 W/c. The dimensions of a metal-based PCB are steadier than insulator substances in terms of directional durability. When aluminum PCB and aluminum sandwiches boards were heated from 30 °C to 140 °C, the size changed by 2.5 to 3.0%.

Thermal transmission is ten times faster than with a traditional stiff FR4 PCB. Heat dispersion is far preferable to that of ordinary FR4 structures. Increase power density could be achieved whereas equipment remains cool, extending element life and resilience. Dielectrics can be customized to meet your thermally and insulating needs. Systems with efficient cooling qualities can be driven harsher or de-rated for lower-cost materials.

It is possible to obtain the simplicity of both a heating sink and a PCB. That ensures you have not only the thermal properties of a heating element but also a PCB layout that is both cost-effective and small. This always allows for quick heat clearance from Led technology to avoid burns. By combining a dielectric polymeric covering with high thermal conductance levels, a decreased thermally resistivity could be achieved. The heat is dissipated by the laminates in the MCPCB, providing optimal heat managing and, as a result, longer operational life and improved productivity.

Metals PCB Layout and Variations

Aluminum cores PCBs, Copper cores PCBs, and Iron cores PCBs were the 3 types of metals PCBs now available on the marketplace, with Aluminium core PCBs being the most useful. The following is a common metal pcb fabrication.

1. Metallic Base

A metal-based PCB (MPCB) is made up of metallic substrates (such as aluminum, copper, or stainless), thermally conductive insulating, and copper circuits. MPCBs were employed in a wide range of industries because of their exceptional heat dispersion. They’re commonly found in power supplies, LED lights, and other places where heat is a significant problem.

2. Dielectric

The dielectric overlay is laminated along with a copper layer on the surfaces on an anodized, protected metals foundation. It is normally 50-200um thick and serves as an insulated covering. This could work as an insulating to avoid short-circuiting with the basis of the metal if it is too thick, and that will reduce heat dispersion. This could disperse heat efficiently if it is too thin, but it is simple to short-circuit.

3. Copper

To boost peeling resistance, the backside of the copper foil is chemically oxidized, and the surfaces were galvanized and brass plating. Copper was generally 0.5/1.0oz-in mass.

Why is it necessary to utilize a metals PCB?

Dissipation of Energy

Most double-sided and multi-layer PCBs were currently high-density, high-power boards with poor heat dissipation. Conventional platforms, including FR4 and CEM3, have poor heating conductivity because they are enclosed among levels, and heat could not be dispersed, resulting in a high-temperature breakdown of the components. Protected metals substances, which have a heat dispersion capability 5-10 times that of FR4, could address this issue.

Expansion Due to Heat

Resin, reinforcement materials (such as glass fiber), and copper foil make up traditional printable circuits boards. In the Z-axis dimension, the thermal expansion coefficient (CTE) of the substrates, whereas the CTE of copper, implying that the CTE of the metalized hole walls and the insulation ceiling of a typical Printed Circuit Board are vastly different. If the produced energy is not removed promptly, thermally expansions and contractions would shatter the metalized holes, resulting in faulty electronic devices.

That issue is exacerbated by SMT (Interface Mounting Technologies). Because the contact is made by solder directly across the metallic pads and the SMD, the CTE differential among the ceramics chips and the FR4 substrates was likely to induce connections fracturing over time. The metals PCB could efficiently control the thermal transfer issue, reducing thermal expansions and contracting and enhancing the electronics equipment’s lifetime and dependability.

Stabilization in Dimensions

In terms of dimensions, a metal PCB is far more dependable than a regular PCB. For instance, the dimension variation of an aluminum core metals PCB heated from 30°C to 140°C is 2.53%. High heat dissipating substances protect parts from overheating and damages, and a metals cores PCB or an aluminum cores PCB may be the best option because it effectively works as one giant heat sink.

Interested to know more about Metal Core PCB boards, or PC Board Assembly contact us at sales@pnconline.com.

PCB FABRICATION SUBSTRATES

PCB FABRICATION SUBSTRATES

What is PCB substrate?

Every home is required to have a solid foundation. A substrate is also required for every printed circuit board. The actual substance that contains the traces and elements is known as the PCB Fabrication substrate. The first step in creating a high-quality PCB is selecting the correct substrate. Structure and shape are required for a PCB. It also requires a platform or canvas on which to place all of its other components. The PCB’s performance is influenced by the substrate’s properties. A stiff substrate, for example, can improve the PCB’s strength and endurance. More design options are available with a flexible substrate.

The usage of a variety of substrates, ranging from solid fiberglass to flexible polymers, is becoming more common as the PCB industry evolves. Fiberglass has traditionally been the most prevalent type of substrate. It’s a low-cost, high-reliability material that gives the PCB a nice, stable foundation.

pcb board
pcb board

 Material of PCB substrate

It’s only reasonable that the materials you choose have an impact on your product’s performance. It’s the same with printed circuit boards, where selecting the correct PCB substrate materials can have a significant impact on the board’s performance, durability, and other characteristics.

printed circuit board
printed circuit board

Types of PCB substrate material

Following are the good material that we need for PCB substrate.

1. Copper foil:

PCB substrate materials are critical in defining the board’s endurance and quality. Manufacturers appear to be attempting to go towards fine lines and high density. You may be familiar with the term HDI PCB. This is the abbreviation of High-Density Interconnect Printed Circuit Board. To be classed in the HDI category ten years ago, a board had to have a line space (S) and line width (L) of less than 0.1mm. Today’s standards differ from one industry to the next. S and L on electronic devices are frequently set as low as 60m, and in advanced applications, they can even go as low as 40m. Once a thin copper foil substrate is applied, S and L can reach as low as 30m during circuit design development. The ideal thickness is between 9 and 12 meters.

The issue is that a thin copper-coated laminate can be costly and prone to flaws. It’s the most plausible explanation for why corporations use 18-meter-thick copper foil. However, if S and L are less than 20m, normal thickness copper foil may not be the best option.

pcborard
pcborard
 2. Dielectric Insulating Coatings:

The ability to build up is a key feature of HDI printed circuit boards. There’s a good probability you’ll be able to construct an appropriate circuit if you utilize resin-coated copper (RCC) or combine copper foil lamination with epoxy glass prepreg cloth. MSPA and SAP techniques have also been implemented by the manufacturers. By using an insulating dielectric film lamination with chemical copper plating, the copper conducting plane was created. The fundamental reason we can make acceptable circuits is because of the thin copper plane.

3. High heat protection and dissolution are required:

Electronic devices tend to generate more heat as the trend toward downsizing and high function continues; hence thermal management of electronic devices is becoming increasingly important. Thermal-conducting PCB research and development is one of the solutions to this problem. The main criteria for a PC Board to operate well in terms of heat resistance and dissipation are the substrate’s heat resistance and dissipation capacity. Improvements in thermal-conducting capabilities of PCBs are now being made through epoxy and filler additions; however this only works in a limited category. The most common way is to use IMS or metal core PCBs as a heating component. This system has several advantages over the typical radiator and fan, including a smaller amount and lower cost.

How to Select Substrate Materials for PCBs

You can choose between three distinct types of PCBs:

• Rigid
• Flexible
• Flex-rigid

The most important goal is to select a board that is ideal for your product. Many people strive for compact size and shape while overlooking performance. Polyimide film is a good choice since it is adaptable and can be used in a variety of applications, including black, white, and transparent. It also ensures a low coefficient of thermal expansion while keeping acceptable heat resistance. The Mylar substrate, on the other hand, is extremely flexible and resistant to external conditions. Furthermore, it is reasonably priced, which is why many consumers consider it. Flexible PCBs must attempt to achieve the same degree of frequency and speed performance as regular PCBs. Flexible boards can be made with advanced polyimide substrates and polytetrafluoroethylene.

Flexible boards are used in a variety of industries, including medicine, smartphones, and gadgets. As a result, the market has been implementing innovations in flexible and ultra-thin multi-layer boards (0.2-0.4mm). You can expect flexible boards to achieve speeds of up to 5Gbps at this time, but you’ll need to choose a substrate material with a low Dk/Df. It’s also a good idea to utilize conductors with a thickness of above 100m, as this will aid with current and power handling.

Best PCB substrate type

A substrate and printed wires are the two main components of a PCB (the copper traces). Substrates that divide the layers are required for multi-layer boards. The substrate works as physical support for the circuit components and printed wires, as well as providing electrical insulation between conductive portions. PCB Substrates are non-conducting materials. They act as a laminated electrical insulator between circuits for this purpose. An electrical insulator is a material that does not conduct electricity because its internal electric charge does not flow freely. As a result, plated through holes are used to connect traces on opposite layers on each layer of circuitry.

A substrate and laminate are commonly used as the foundation or base of a printed circuit board (PCB). The performance of the PCB is determined by the type of laminate and substrate used. As a result, choosing the proper types of PCB material for the job is crucial to getting the greatest results. Any PCB design guide should include such features:

 Working
 Durability
 Cost-effectiveness

The material you choose for your PCB can have an impact on its short- and long-term functionality, along with your contractor’s capacity to build it. You can’t blame the contractor if you buy substandard materials and they fail when your contractor tries to make the board. When maximum performance isn’t a must-have feature for a PCB, lightweight polyester material is typically a fine option. As long as lightweight polyester is utilized in conjunction with printed electronics (PE) technology, there are at least two reasons to choose it in these circumstances. Printed electronics with lightweight polyester have these features:

Cost-effective Lightweight polyester produces less waste, necessitates fewer manufacturing steps, and eliminates the need for desalination and purification.

Adaptability Flexible printed circuits (FPCs) are available, but the level of “bendability” that makes them so appealing is costly to accomplish. PE with lightweight polyester maintains flexibility at a far cheaper cost.

Traditional PCBs, on the other hand, is still the top choice for high-performance applications, and the materials used in their construction should be determined by the type of board required. For example:

 Manage frequencies ranging from 500MHz to 2GHz
 Allow for high power and, as a result, high temperatures
 Be “intense” and complicated
 Manage microwave and above-microwave frequencies

The board’s application decides the substrates and laminates to utilize to a considerable extent. There are five types of substrates, each with its own set of features for specialized purposes.

1. FR-4

Fiberglass substrates are comprised of woven fiberglass that has been impregnated with only a flame-retardant substance. The material is rigid and can be drilled, cut, or machined, although tungsten carbide tools are required due to the abrasive nature of the fiberglass. An FR-4 substrate is more resistant to cracking or breaking than an FR-2 substrate and is typically seen in higher-end devices.

2. RF
Low dielectric polymers are employed in RF substrates, which are used in printed circuit boards for high-power radio frequency applications. Despite its low mechanical qualities, the substrate exhibits remarkable electrical performance.

3. FR-2
This extremely low substrate is comprised of impregnated paper, also known as Phenolic, and is simple to the machine over a fiberglass substrate. Flame Resistant is denoted by the letter “FR.” This substrate is commonly encountered in lower-cost consumer devices.

4. Flex
Flex circuits are those that are meant to be very flexible or slightly flexible. As substrates, thin, flexible polymers are used. Although the manufacturing process is more complicated than utilizing rigid substrates, it provides benefits that rigid substrates cannot, such as reducing space by bending the circuit board to fit a specific place or where repetitive action is essential. A low-thermal resistance substrate is required for power electronics. A ceramic core or metalcore substrate has the essential properties to accommodate larger copper tracks and the high electrical currents that these circuit boards require.

Final Thoughts

Every substrate has its uniqueness and you get to know almost every substrate detail in this write-up. Interested to know more about our facilities at PNC? Contact us at sales@pnconline.com

HDI Printed Circuit Board

HDI Printed Circuit Board

HDI boards, another of the highest technology in PCBs, also are accessible at Incredible. HDI Panels have blind and hidden visas and typically include MicroVAX of .006mm or below in size. They feature a greater circuit complexity than ordinary circuit boards.

What is HDI PCB?

HDI stands for High-Density Interconnector. Any SATA connector with a greater wire volume per square meter than a regular board is termed HDI circuit board. HDI PCBs feature narrower gaps and outlines, more minor visa and grab pads, and increased connecting pad frequency. It is beneficial in boosting electrochemical characteristics and lowering the shape and volume of the device. HDI PCB is the superior alternative for the supervisor/ and pricey laminated PCBs.

HDI PCB
HDI PCB

The circuit should have different characteristics for high-speed signal electrical demands The thickness of the board should be increased by downsizing and configurations of the electrical components. The board is also highlighted with outstanding high density, thanks to the assembly procedures for leadless, fine pitched packaging, and simultaneous chip connection.

Difference between standard PC Board and HDI PCBs

HDI naturally offered superior system reliability than non-HDI since the use of tiny blind and entered visas reduces all stretching capacities and inductivities. Because there are no gaps, MicroVAX resistance is near the trace frequency. The straying capacitance of a typical passage is substantially larger, resulting in more impedance irregularity than a sensor. The following are some of the main distinctions between HDIs and regular PCBs:

Typical PCBs:

  • Less than HDI
  • Bigger and heavier panels
  • Through-holes
  • Thermal mechanics
  • Higher layer numbers
  • May experience low-pitch performance issues

HDI PCB:

  • Higher square inch component concentration
  • Smaller, thinner, more useful PCBs
  • Blind, concealed, and MicroVAX solution
  • Direct optical drilling
  • Medium access number
  • increased pin count and small pitch compatibility packages

Layout for HDI?

High-density (HDI) interconnection design refers to a series of strategies to design a PCB where trace widths typically decrease around eight miles (0.2 mm). These strategies are meant to guarantee that your plates remain compact, and element count is increased to a greater density of systems into a single panel. Not all circuits need HDI designing approaches for a myriad of purposes, whereas certain parts require HDI approaches for effective routing.

An HDI board needs smaller vias to achieve layer transformations, especially for BGA great devices and more lines per mm2. For exemplary pitch modules, the following common characteristics are included in an HDI structure:

HDI
HDI

Ø Smaller vias:

For layer changeover, HDI boards typically employ microvias or laser-bound, delusional, and stagger vias. Such pathways have a lower refresh rate than usual pathways. Their widths are lower, and their practical depth is consequently limited to employ these Vias using fine-tuning components.

Ø Diluted traces:

The smaller trails used in HDI panels are necessary to link the vias on every layer and the in-pad vias. These smaller traces permit increased trace frequency, the name HDI.

Ø Count of higher layer:

the constructed of non-HDI panels with large layer numbers, but when dealing with high pin frequency electronics, HDI layer numbers may quickly exceed 20 may be more layers.

Ø Lower levels of signal:

For high frequency or high tides, HDI circuits are not utilized. The elevated field strength between adjoining lines causes ESDs, and high tides create an excessive increase in conductive temperature.

Looking at the above criteria and IPC requirements, you may determine whether a board is transitioning to the HDI system, which requires HDI design and routing technology. The current permissible aspect ratio for through-the-hole vias is 8:2 as per IPC-2321A/IPC-2422 regulations (aperture = via detail diameter). This indicates that the lowest drill diameter for a cross hole through a normal thickness of 1,56 mm PCB amounts to 0,197 mm or ~8 miles. As your Via has to be shorter to enable fine pitch parts, certain HDI specialized modules must be used through layouts and smaller traces.

HDI PCB advantages:

The virtual world becomes sophisticated day by day, while the hardware involved becomes much smaller. There are various benefits of HDI PCBs, beginning with greater connectors in smaller regions. As a consequence, boards may be miniaturized in diverse fields.

Your devices are not hefty anymore. They’re smart and attractive. You can operate on your notebook and keep your company going on a trip. You may also view your smartphone’s favorite action film, some quite strong compared to your computers. Or you may connect in and then get into the rhythm with your wireless earbuds. The human race loves technology, and it has become a part of everyone’s life. All electrical equipment was built for mobility at this time. Electronic gadgets for recreation purposes are developed. All this was feasible because the parts and PCBs within the electronic gadgets were miniaturized.

In developing all electrical devices, the PCB sector plays a vital role. Maybe this will be a pacemaker or chipset at a software’s workstation; PCB allowed the creation of critical digital equipment.

1.   Fantastic flexibility:

HDI circuits are appropriate for those who focus on weight, economy, dependability, and efficiency.

2.   Easy installation:

The integration of blind visas and MicroVAX reduces the space need.

3.   Better integrity of signal:

HDI includes technology through inside and blind. This helps to bring the circuits closer together, which reduces the length of the signal route. The HDI feature reduces through stubs and decreases signal distortions, and improves system performance. It enhances the signal integrity considerably owing to shorter signal routes.

4.   Signal Credibility:

Stubs and their impact on signals and data transmission rate reduction

5.   High certainty:

Stacked visas give these panels fantastic protection against harsh environments.

6.   Cost-effective:

The capability of a normal 8-layer PCB may be lowered without losing quality to work in a real HDI board.

Why using HDI:

HDI boards are particularly attractive to portable, mobile, and portable electronics due to their slim, dependable performance and tiny size. These heavier, small molecules and extra transistors interact with the layout of and improve skills to increase the performance of the Printed Circuit Board and the finished result for which it is employed.

Electrical signals require reduced time to travel with equipment closer to one side. The elevated design of HDI panels decreases the signal increases and the capacitance, reducing the impact on surrounding pins and pipes. Additional circuits provide not only an improved user experience but also greater performance.

Focusing on HDI architecture reduces the time and expense of growing prototypes, shortens lead times, and provides a substantial cost advantage.

o   Automotive:

Automobile makers are very attracted by compact PCBs because they can also save room in the car. The merging of technological gadgets to create better driving dynamics was the emphasis of carmakers on future automobiles from firms like Tesla.

o   Medicare:

The HDI PCB influences the medical sector. Medical equipment is frequently HDI since it can integrate into compact devices such as implants, laboratories, and imagery. Medical devices play a key part in illness diagnosis and support life. Ex: defibrillators, patient monitoring equipment.

The inside section of the patients may be viewed, and the correct diagnosis may be obtained using the tiny camera dimensions. The cameras are becoming smaller, yet the quality of the image is not affected. The HDI PCB was developed to enable these advances to be accommodated.

The sensors that have to be placed from equal angles, which some people consider discouraging, have decreased in size with a higher quality of images. Doing a colonoscopy will no longer hurt a lot.

Tablets and smartphones:

All cellphones are ELIC-built HDI PCBs (Each Layer Connectivity). Smaller transportable electronic gadgets are responsible for generating thinner HDI PCBs.

o   Aerospace and military:

HDI is included in secure systems and other critical equipment such as missiles and defensive systems. The HDI PCBs are appropriate for severe and dangerous settings, making them perfect for aircraft and medical operations.

o   Wearable devices:

HDI has become a key consumer player by launching Apple Watch and other accessories such as VR headsets. Digital devices have become popular with the youthful generation because of their outstanding utility.

HDI board types:

A range of vertical goods includes HDI boards, such as missile guidance makers and essential devices and diagnostic devices. The lightweight of HDI panels is also excellent for the aerospace industry and smaller laptops and smartphones.

These are some renowned circuit boards of HDI manufactured.

  • Using surface-to-surface vias
  • Confluence through vias and entered vias
  • Multiple layers of HDI contained through
  • A passive substratum without electronic components
  • Coreless design by using layer sets
  • Alternate coreless buildings by using layer groups

Final Thoughts

HDI circuits are appropriate and preferable for most applications relating to aviation, consumer items, electronic components. Due to its powerful connection of stacked vias, HDI boards with many layers provide greater durability even in intensive environments.

The decrease in pressure gradient creates more room for designers to work, opening up the bare PCB to both edges for design. More closely located smaller components generate greater interfaces, enabling faster communication capability and a significant decrease in bridging delays and loss of signal.

The HDI model enables the 8-layer hollow Printed Circuit Board to be reduced to a 4-layer HDI microplate, with fewer layers capable of providing the same or superior performance. This decrease significantly reduces material prices, making HDI innovation for electronics makers more economic. The higher efficiency of micro HDI PCBs makes them dependable even in demanding settings.

At PNC, you will get your HDI circuits done at an affordable rate. Contact us at sales@pnconline.com.

HDI_Printed_Circuit_Board_1280x300

What’s a HDI Printed Circuit Board?

HDI stands for High Density Interconnect. HDI PCBs have finer traces and trace spacing, laser drilled micro vias and higher connection pad density. Its two chief advantages are that it permits the use of fine pitch BGAs and it reduces the number of PCB layers required because the finer traces and smaller vias allow more circuitry in a smaller area.

Narrow trace widths mean higher circuit density

At PNC standard PC Board fabrication uses a minimum trace width of 5 mil, with a 5 mil space between traces (5/5mil) PNC’s HDI trace widths can be as narrow as 3 mil with 3 mil spacing.  These finer traces allow 160% more traces in the same real estate. 3/3mil spacing will also allow two traces to escape between pads of a standard BGA, meaning less PCB layers are needed to fan out the pins from the BGA.

Microvias are the enabling technology for HDI

Narrow trace widths used in HDI PC Board are a result of the gradual refinement of photolithography and etching technology.  Microvias on the other hand, are a revolutionary innovation driven by the development of high powered lasers that can be controlled accurately enough to ablate a 3 mil hole through the surface layer of copper and underlying laminate, without damaging the underlying layer of copper.

The minimum hole size for PNC’s laser drilled microvias are 3 mil and the minimum pad diameter for the microvia is 7 mil.  Pads for laser drilled holes can be smaller than for mechanically drilled holes because of the location accuracy of the laser drilled hole.  There is no mechanical deflection of the drill bit to account for.  The laser drilled holes can be fully copper filled and planarized flat, so they can be used as pads for fine pitched BGAs with 0.4mm or smaller spacing. Using microvias as pads allows the signal trace to fan out by going straight down and out to an inner layer of the printed circuit board.

The biggest limitation with microvias is the aspect ratio of the holes.  Where a drilled through hole can have a 10:1 depth to diameter aspect ratio, a laser drill can achieve no more than around a 1:1 aspect ratio.  This means that the smallest microvia can only connect two adjacent copper layers. A larger diameter microvia can penetrate two layers. To connect deeper layers, the designer must stack vias one directly atop another.

Laser drilling of the microvias changes the way PCBs are fabricated and gives the designer flexibility that they do not have with through hole vias.  In a standard drilled PCB, via holes are drilled and plated after the PCB fabrication stack-up is completed.  Because the microvias can only bridge two or three copper layers, the microvias must be drilled and plated at each lamination step.  This means that microvias can be fully buried between layers, stacked or staggered to allow the microvia to connect multiple layers of the stack up.

The major space saving advantage of the microvia technology is that vias can just connect traces that need to be connected, rather than taking up real estate all the way through the PCB the way a through hole via does.

The Printed Circuit Board designers at PNC take advantage of this by locating the power and ground layers at the top of the stack up.  Since all active components access power and ground, sometimes through multiple pins, having the power and ground layers directly below the component layer allows all those connections to be made directly by microvias.  This leaves the component layers and layers beneath the power and ground layers completely unobstructed for signal routing. This has the added advantage of reducing parasitic capacitance because it eliminates the circuit stubs caused by plated through holes.

Two sided boards are typically fabricated with a combination of through holes and microvias.   Though holes can be drilled just through the core, connecting the stacks on the top and bottom of the board from the lowest layer, or through holes can be drilled through the entire stack directly connecting the traces on the top and bottom component layers.

 

HDI PCBs are a necessity when using fine pitched BGAs, but they can also reduce cost on PCBs without fine pitched BGAs because of the reduced layer count.  On your next PCB design, talk to the experts at PNC.  They can help you determine if HDI technology is can reduce your PCB cost by reducing layer count and shrinking the PCB size.

BGA-HDI

Better BGA routing on a Printed Circuit Board with High Density Interconnect

One of the technologies that have allowed electronic products to shrink in size and provide increasingly higher performance is the ball grid array (BGA) IC package. The BGA allows higher density PC Board layouts because of simple geometry. The number of pins that can be accommodated on the perimeter of a quad pack increases linearly with package size. The number of connections that can be accommodated on a BGA increases with the square of the package size. BGA packages now routinely exceed 1000 connections, and the ball pitch has shrunk from 1.0 mm to .8 mm to a growing number of devices now available in the micro-BGA format with a ball pitch of .65 mm, .5 mm and smaller.

The decrease in BGA ball pitch would not have been possible without the improvements in PCB fabrication. These improvements, collectively called High Density Interconnects or HDI, give companies like PNC the capability of creating traces as narrow as 0.0762 mm (3 mil) and vias with annual rings as small as .25 mm (10 mil) HDI PCB fabrication has given designers greater flexibility in routing BGA devices down to a pitch of .65 mm The HDI technology is essential for devices with ball pitches less than .65mm

Routing the hundreds of connections from a typical BGA is called BGA breakout, and it can be a major layout challenge. For this reason, many designers place the BGAs into the layout first and fan-out the connections from each pad to a stub trace. This allows the designer to adjust the routing of individual pins under the BGA without rerouting the entire PC BOARD. Another reason the BGA should be placed first is that the BGA breakout will likely dictate the number of layers needed in the PCB stack-up.

The breakouts are typically a repeating pattern, with the traces for each row of balls around the perimeter routed similarly. Most BGA manufacturers will provide sample breakouts, and some high-end tools will automate this breakout process. Most BGAs use similar fanout approaches, the fanout differing only in the package specific routings for power and ground. With standard PC Board fabrication technology there really are not a lot of fanout options. Here is the typical approach used for BGAs with pitches down to .65 mm highlighting some of the advantages of PNC’s HDI fabrication technology

Routing the first perimeter row of the BGA is easy; the traces come straight out from the pads.

The traces for the second row pass between the pads of the first row. If the ball pitch is greater than .8 mm an HDI PCB fabricator with the capability of creating 3mm pitch traces can fit two 3mm traces with 3mm spacing between the pads in the outer row. This allows the first three perimeter rows of pads to be routed on the top layer.

Subsequent rows are routed using a feature called a dogbone. The dogbone has a pad at one end and a via at the other, separated by short trace. This prevents the via from wicking solder from the ball pad, starving the solder joint. It is also recommended to cover or “tent” the dogbone via with solder mask. The dogbone is typically oriented at 45 ° so that the via can be located in the center of each four pad grid. The via takes the signal trace to the next level where it is routed out between the other vias, similar to what was done on the top layer.

the following number of board layers typical are needed for each perimeter row of pads

board layers
board layers

This table demonstrates that using an HDI Circuit board fabrication process, even for a 1.0 mm or .8mm pitch BGA can result in the need for fewer signal layers, because two traces can be passed between each pad. The HDI fabrication process also allows the dogbones to be placed in line with the grid instead of diagonally, which allows two traces to pass between vias on the 2nd and 3rd layers

For smaller pitch devices PNC’s HDI fabrication techniques become essential. For ball pitch spacing of .65 mm and .5 mm the only way to create a fanout is using the 3 mil traces and 10.68 mill dia. vias allowed by HDI. The 3 mil trace and 3 mil trace spacing allows a single trace to just fit between .5 mm pitch pads.

The latest micro BGAs used in devices like phones and smartwatches have pitch spacing below .4 mm. The pitch spacing is so close that traces no longer fit between the pads. BGA breakout requires via in pad techniques, with the filled microvias routing the signals straight down and then out. Depending on the number of perimeter rows, blind and buried vias may also be needed.

If you are using a BGA in your design, using HDI design rules for fabrication can simplify the breakout and reduce the number of PCB layers needed. PNC engineers can help you understand what is possible with HDI Printed Circuit board fabrication.
The last thing to know about designing with BGAs is that process yield, and reliability are very process dependent. When selecting a
Pga Capabilities
it pays to select PNC. PNC has the equipment and expertise to manufacture your most challenging BGA designs.