Metal Base Heat Dissipation Board
The most important recent advances metal core PCB manufacturers have made in PCB board industry are the development of new board substrates. It can withstand high temperatures, along with metal cores for improved heat transfer, and selectively apply thicker copper to specific tracks, pads or planes to increase current carrying capacity. Getting the most out of these advances requires a deeper understanding of how boards in general are made.
What is a Metal Core PCB?
This is a special Printed Circuit Board that contains a metal core. This metal core facilitates the dissipation of heat generated by circuits and surface-mounted components, enabling finer circuit patterns and high-density chip packaging.
Metal Heat Dissipation Board
What is a Metal Heat Dissipation Board?
The metal heat dissipation board is a printed circuit board with enhanced heat dissipation. It is used when efficient heat dissipation is required, such as LED lighting, power devices, and parts that generate a large amount of heat.
Types of Metal Heat Dissipation Boards
You can select a structure in which a base substrate that forms a circuit on a metal such as aluminum or copper, a core substrate that sandwiches the metal inside the substrate, or a part of the copper base or copper core has direct contact with the circuit formation.
The thermal conductivity of the insulating layer has a great effect on improving heat dissipation with a metal heat dissipation board.
Metal Core Board Production Method
It is a manufacturing method of a metal core substrate in which insulating layers are laminated and integrated on both the front and back surfaces of a core plate with holes, and then a metal core substrate is manufactured and separated into each metal core substrate by external processing.
In the drilling process of making a hole in the core plate, a dividing portion that divides the inside and outside of the virtual outer machining line that is cut in the subsequent outer machining process with a gap as a boundary, and the divided portions are separated from each other. Connecting parts that connect the inside and outside across the virtual outer shape processing line are formed alternately and continuously.
Metal Core PCB Board Manufacturers Laminating Method
In the laminating step of laminating, the resin constituting the insulating layer is filled in the divided portion.
In the subsequent stage from the laminating step, at least a part of the connecting portion is removed by drilling, and a dividing step is performed in which the connecting portion is divided into the inside and the outside with a gap as a boundary.
In the outer shape processing process for performing the outer shape processing, the metal core substrate is separated by cutting at the outer shape processing position.
An insulating coating portion made of a resin constituting the insulating layer and covering the end face of the core plate is formed on the outside of the end face of the core plate that has formed the divided portion of the core plate.
How do Metal Core PCB Board Manufacturers Make MCPCB Boards?
The metal core substrate is manufactured by putting a copper-clad laminate manufactured by laminating and integrating an insulating layer and a copper foil from the inner layer side on both the front and back surfaces of a core plate having a predetermined hole into a line.
In the line, through holes are formed, plated, and patterns are formed on the copper-clad laminate (work), and multiple products (wiring patterns are formed on the copper-clad laminate) are formed on one work. Metal core printed wiring board) is formed. These products are individually separated by external processing, and the production is completed after undergoing a predetermined inspection or the like.
In the outer shape processing, the laminated portion of the core plate and the insulating layer, which are laminated and integrated into one sheet, is cut. Therefore, when the end face gets wet due to moisture absorption or dew condensation, it is considered that the insulation property with the wiring pattern 104 on the surface layer may deteriorate. Therefore, especially when the inner layer is used as electrical wiring, migration measures are required.
In addition, since the outer shape is processed on a part of the core plate, there is an inconvenience that burrs and sagging occur. This is because mold processing is generally used for external shape processing.
That is, router processing, which is another method of external shape processing, is a method of cutting by tracing the end face of the work material with a circular bit like a drill with a blade on the side surface, so that a large amount of material can be processed in a short time.
Although there is a drawback that the processing cannot be performed, the mold processing is a method of punching using a die and a punch, and has an advantage of high productivity, so that the mold processing is often used.
How to Form Insulating Layers on Metal Core Substrate?
The first means for that purpose is a metal core substrate obtained by forming insulating layers on both the front and back surfaces of the core plate to form the metal core substrate and then separating the metal core substrate by outer shape processing, and the outer shape processing is performed.
At least a part of the outer peripheral edge portion has an end face of the core plate recessed inward from the end face position of the outer peripheral edge portion and an insulating coating portion made of a resin constituting the insulating layer and covering the end face of the core plate. It is a metal core substrate on which an insulating structure is formed.
The second means for solving the problem is to manufacture a metal core substrate in which insulating layers are laminated and integrated on both the front and back surfaces of a core plate having holes, and then a metal core substrate is manufactured and separated into each metal core substrate by external processing.
In the drilling step of drilling a hole in the core plate, a dividing portion that divides the inside and outside of the virtual outer machining line that is cut in the subsequent outer machining step with a gap as a boundary.
Then, in the subsequent stage of the laminating step, at least a part of the connecting portion is removed by drilling, and a dividing step of dividing into inside and outside with a gap at the boundary of the virtual outer shape processing line is performed, and the outer shape processing is performed.
In the process, the metal core substrate is cut at the external processing position and separated into each metal core substrate, and the end surface of the core plate is made of a resin constituting the insulating layer on the outside of the end surface of the core plate that constitutes the divided portion of the core plate. It is a method of manufacturing a metal core substrate that forms an insulating coating portion that covers.
Importance of Substrate in PCB
Printed Circuit Boards (PCBs) are made from a wide variety of materials and popular formats when high reliability, insulation strength and thermal performance are required. Such is FR-4, in which the substrate is woven glass fabric impregnated with epoxy resin.
When the substrate is fully cured with copper foil laminated to the top and bottom, it is called a core. If the epoxy is not cured and copper is only on one side, then it is called a prepreg and it is hot-pressed with a core to form a multilayer board.
There are two things that most limit a PCB’s top temperature rating. This is the difference in Coefficients of Thermal Expansion, CTE, between the copper and the substrate, and it must be adjusted with the adhesive connecting the two and the type of substrate.
The standard epoxy used in FR-4 has a glass transition temperature, Tg, of 130 C, from which it becomes rigid to significantly more flexible and worse, also experiences a dramatic increase in CTE. Long-term operation near, much less Tg will ultimately lead to board failure due to cracks and tear marks, interlayer shorts and even complete delamination of copper from the substrate.
Although leaded solder requires heating up to 225 C during infrared reflow soldering in order to completely moisturize the joints.
How does Mcpcb Board Control Heat Management?
Metal core PCBs (more formally known as insulated metal substrates) take a different approach to temperature control, improving the thermal conductivity of the board itself. This allows the board to more efficiently transfers heat from components to the environment, reducing the size of additional heat sinks or even eliminating them entirely.
The metal core board uses a metal plate as the core of the FR-4 board. The metal plate is much thicker than the copper foil used for footprints – typically 0.8mm to 1.6mm, and most commonly aluminum or copper.
Why Do Metal Core PCB Manufacturers Choose MCPCB Board?
Because the metal core pcb provides significant stiffness, a very thin dielectric layer can be used between it and the copper layer to provide electrical insulation at much higher thermal conductivity than the FR-4 equivalent fiberglass and epoxy thicknesses. The end result is a dramatic increase in thermal conductivity from a typical value of 0.25 W / mK (watts per meter Kelvin) for the FR-4 to 3 W / mK for a single sided metal core board.
However, much of this advantage in improved thermal conductivity is lost when switching to a double-sided board. Another potential problem is that the core itself is electrically conductive, so it is more difficult to provide good electrical insulation between it and the through holes or through holes of the component.
Some board manufacturers lay all alternating layers of copper and dielectric film on one side of the core to maintain a low thermal resistance between the core and heat sink and bypass the problem of through insulation.
This is due to the higher thermal resistance between the fuel component and the core. Thus, metal core PCBs is best reserved for relatively simple power electronics devices that don’t need to worry too much about signal integrity issues or maintain tight control over parasitic inductances and capacitances.
Boards that can withstand higher temperatures or dissipate heat more efficiently are certainly welcome improvements for power electronics engineers, but the big Kahuna is the ability to carry more current for a given route width, and that is what heavy copper PCBs are.
Three Ways to Increase the Thickness of Copper on PCB
There are three ways to increase the thickness of copper on a PCB:
- Use thicker foil for the blank board.
- Applying additional copper to the board after etching;
- Applying additional copper only on traces and gaskets, which actually carry a large current.
The first approach quickly becomes untenable with increasing copper thickness. Starting with 0.7mm pure copper foil. Then etching it onto the substrate to form individual tracks will take a long time, and will also result in heavy undercutting.
What Happens If We Apply More Copper?
Therefore, applying more copper to an already drilled and etched board appears to be the preferred process, although the main caveat here is that copper will also deposit on the sidewalls of the tracks and through holes, reducing the distance between the tracks and possibly blocking the holes. Hence, for heavy and extreme copper boards, more generous footprint rules are required.
Associated with this is the problem that the minimum size of spacers, traces and vias increases with the weight of the finished copper until it becomes impossible to accommodate smaller components.
However, both of the above problems are improved, if not eliminated, by selectively applying heavy copper to only those traces that need it. The board can now have, say, 10 oz copper for the power circuit and 1 oz copper for support circuits that need to be in close proximity, such as gate drivers, feedback shaping.
It is the ideal solution for three main issues: no PCB CAD software, no solder paste stencil printers, no gripping machines. Never before have you had to deal with different copper thicknesses on the same board in placement. Depends on CAD software and PnP machine. The final drawback is the price of selective heavy copper, and at least one board supplier warns that the cost can be frustrating for all but military and aerospace applications.
However, the potential reduction in assembly labor (excluding solder paste application), along with improved heat dissipation and tighter integration of power and support circuits, could outweigh the higher cost of selective heavy copper to such an extent that it is compelling even for the infamous costs.
Why do Metal Core PCB Manufacturers Require Modern Technology in PCB Board Manufacturing?
Modern technology cannot be imagined without printed circuit boards (PCBs), which not only replaced the harnesses of connecting wires and sockets for fastening electrical radio products (ERI) in electronic devices, but also created a new culture of development and design of equipment, and with it – new industrial technologies.
PP production has long been a major industry, one of those that determine technological progress. The volume of production of printed circuit boards in the US in value terms reaches 8.2 billion dollars, and in the world market as a whole – 27.3 billion dollars.
PCB manufacturing using traditional technology is always associated with the presence of harmful emissions into the environment. When manufacturing 1 dm2 of a printed circuit board, 0.4 kg of salts, acids, alkalis, dissolved in 100 liters of water, goes into waste to be collected.
In the manufacture of PP, materials of 82 names are used (among them – such expensive ones as foil-clad fiberglass, copper, etc.), a significant proportion of which goes to production waste.
The Role of Traditional PCB Manufacturing Technology
Traditional technology does not allow solving a number of serious problems, such as, for example, providing heat removal from the ERI, which determines the reliability of the equipment and an increase in the density of the elements of the PCB pattern.
With the development of traditional PCB technology, domestic manufacturers have faced problems that cannot be solved by purely quantitative changes, without applying a qualitative approach. Thus, for example, the widespread displacement of components with pins located around the perimeter of the package, components with a matrix arrangement of pins has led to an increase in the number of board layers and the use of “microvia“.
In addition, the use of lead-free soldering technology has dramatically increased the requirements for the materials used. Boards that meet the new requirements are produced in China by only a few enterprises, so complex boards will most likely have to be purchased abroad.
Currently, research and development work is underway aimed at overcoming these difficulties by improving traditional technology. However, this approach does not allow us to fundamentally solve the problem.
So, the cost of wastewater treatment is 5% of the working capital, while the absence of emergency discharges is not guaranteed. In the USA, Japan and Europe, firms spend up to $ 0.8 billion a year on the creation and maintenance of treatment facilities.
The problem of recycling waste foil-clad plastics formed during the production of PP, as well as spent PP in China, is not solved at all.
The costs of increasing integration by increasing the resolution of the PCB pattern are inadequate to the result obtained; since the traditional technology has practically reached the limit in terms of pattern resolution (the width of the conductors and the gaps between them is 0.1 and 0.2 mm, respectively). The presence of interlayer connecting holes inherent in traditional technology leads to the fact that the PCB area is far from being fully utilized.
The Most Important Technical Solutions that Allow Metal Core PCB Manufacturers to be Implemented are:
- Replacement of foil-clad fiberglass with an insulated metal base;
- Replacement of plated interconnecting holes with metal interconnecting posts;
- Obtaining a conductive pattern by flat machine grinding of a metallized relief;
- A way to ensure high flatness of the metal core of the PP (non-flatness is no more than 1 micron), which is preserved during the process of manufacturing the PP;
- A group method for making any holes in the core of the PP and cutting the PP along the contour by electrochemical milling without burrs and deformation of the base (process speed – 0.5 mm / min);
- Temperature-resistant compound-photoresist , which allows metallization of a conductive pattern at temperatures up to 175 ° C and combines the properties of a photoresist and a durable insulating compound. Moreover, the compound-photoresist after the implementation of the photolithographic function of forming the pattern remains on the PCB as a structural material in the form of a matrix enclosing a conductive pattern;
- Highly porous grinding wheels that allow grinding soft metals (copper, nickel, aluminum, etc.) and polymers at the same time.
Efficiency of Metal Core PCB Bord Manufacturers Technology
Tests of PCBs manufactured using metal core pcb board manufacturers technology have confirmed their full compliance with the requirements of existing standards. The new design of the PCB and the technology of its manufacture have a number of consumer qualities, which ensure their decisive superiority over PCBs made by traditional technology.
1. Pattern undercutting is excluded (in traditional technology, lateral undercutting of conductors is inevitable, which is of a probabilistic local nature, which does not allow organizing reliable mass production of conductors with a width of less than 150 microns). It should also be borne in mind that the use of a protector-protected thin foil (5–9 µm) to obtain narrower conductors, which reduces lateral undercutting, increases the cost of the PCB.
2.The new technology and design of the board make it possible to almost completely eliminate interconnecting holes with contact pads and replace them with transition posts with a contact pad size up to 150 microns.
This, in combination with narrow conductors and gaps, makes it possible to reduce the dimensions of the PCB by 2–2.5 times or by 2–3 times to reduce the number of layers, as well as to shorten the length of communication lines and thereby increase the speed of the device.
3.The presence of a metal core makes it possible to reduce the temperature of the ERI, depending on the dissipated power, by 30–50 ° С and thereby avoid the use of a cooling fan in many cases.
What is the Function of Metal Plate on Board?
Finally, the use of a metal plate glued to the board, which removes heat from the ERI located on the PCB, essentially turns the double-sided PCB into a multilayer one. It not only does not solve the problem of heat removal (due to the presence of a fiberglass layer between the plate and the heat-generating element), but also leads to a sharp (4–5 times) rise in the cost of the product and complication of the technological process.
The studies carried out by the authors have shown that it is possible to create a PCB of a new design using a fundamentally new technology that eliminates the listed problems. The technology is based on a method of obtaining a conductive pattern by grinding with an abrasive wheel, therefore it was named PRIMA (obtaining a pattern by a mechanical abrasive method).