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A Comprehensive Guide to Ceramic PCB Manufacturing Processes1. Introduction to Ceramic PCB Manufacturing ProcessesHTCC, DBC, Thick Film Ceramic PCB Manufacturing, LTCC, Thin Film Ceramic PCB Manufacturing, DPC, AMB, etc. are all manufacturing processes for ceramic substrates. Among them, DPC process and DBC process are two commonly used ceramic substrate manufacturing processes. Although they are both methods for making ceramic substrates, there are some important differences between them. Please continue reading and let us introduce them to you in detail. 2. How are ceramic substrates made?DPC (Direct Plated Copper)l Principle: DPC process refers to a process of directly plating copper on the surface of ceramics, which can be achieved by electroplating or hot plating. DBC process refers to a process of directly combining copper with ceramics, which is usually made by adding oxygen between copper and ceramics and combining them through chemical metallurgy. l Process: The ceramic substrate is pre-treated and cleaned, and a copper seed layer is sputtered on the ceramic substrate using a magnetron sputtering process. Then, the circuit pattern is realized through photolithography processes such as exposure, development, etching, and film removal. Finally, the thickness of the copper circuit is increased by electroplating or chemical plating. After removing the photoresist, the metallized circuit is completed. l Technical key: (1) The bonding strength between the metallized circuit layer and the ceramic substrate is the key to the reliability of the DPC ceramic substrate. Due to the large difference in thermal expansion coefficient between copper and ceramic, in order to reduce the interface stress, a transition layer needs to be added between the copper layer and the ceramic to improve the interface bonding strength. Since the bonding force between the transition layer and the ceramic is mainly based on diffusion adhesion and chemical bonds, metals with high activity and good diffusion such as Ti, Cr and Ni are often selected as transition layers (also as electroplating seed layers).(2) Electroplating holes is also a key technology for the preparation of DPC ceramic substrates. At present, most of the electroplating holes of DPC substrates use pulsed power supply. Its technical advantages include: easy to fill through holes and reduce plating defects in holes; the surface plating structure is dense and the thickness is uniform; higher current density can be used for electroplating to improve deposition efficiency. l Advantages: (1) Magnetron sputtering process (below 300℃℃) completely avoids the adverse effects of high temperature on materials or circuit structures, and also reduces the manufacturing process cost.(2) Thin film and photolithography technology are used to make the metal lines on the substrate more refined (line width size 20~30μm, line alignment accuracy error less than ±196), so DPC substrate is very suitable for electronic device packaging with high alignment accuracy requirements.(3) The surface roughness is less than 0.5um, which is more suitable for wire bonding, precision cooling chip packaging and other requirements. l Disadvantages: (1) The thickness of the electroplated copper layer is limited, and the electron microscope waste wave pollution is large(3) The bonding strength between the metal layer and the ceramic is low, and the reliability of the product is low during application. The process is complicated and the cost is high. l Application: LiDAR, laser emission segment, radio frequency device, sensor, precision micro cooling chip, aerospace and other fields  DBC (Direct Bonding Copper)l Principle: DBC is a technology used for surface metallization of ceramic materials, especially for bonded copper processing of alumina (Al2O3) and aluminum nitride (AlN) ceramics.This technology originated in the 1970s. Its basic principle is to introduce a certain amount of oxygen element on the surface of copper and ceramics, and then in the temperature range of 1000 to 1100 degrees Celsius, copper and oxygen react to form a eutectic phase Cu2O. This eutectic The liquid phase helps improve the wettability of copper on the ceramic surface, thereby achieving a metallurgical bond between the two. During the production process of DBC ceramic substrates, factors such as the oxidation time, oxidation temperature and oxygen partial pressure of the copper plate will have a significant impact on the bonding strength.DBC ceramic substrates are widely used in power semiconductor modules, solar panel components, and insulated gate bipolar transistors (IGBT) and other packaging devices. However, this method also has some shortcomings. For example, using the eutectic reaction of copper and oxygen at high temperatures requires high precision in equipment and processes, and the bonding strength of DBC has not yet met the needs of some specific application scenarios.l Process: Add oxygen element between copper and ceramics, and make it through chemical metallurgy. The Cu-0 eutectic liquid is obtained at a temperature of 1065~1083℃, and then the intermediate phase (CuA102 or CuA12 O,) is obtained by the reaction, thus The chemical metallurgical combination of the Cu plate and the ceramic substrate is achieved, and finally pattern preparation is achieved through photolithography technology to form a circuit. l Technical key: In the preparation process of DBC substrate, it is necessary to strictly control the eutecticity and oxygen content. The oxidation time and gasification temperature are the two most important parameters. After the copper foil is pre-oxidized, the bonding interface can form enough CuxOy Phase wettability of A₂0₂ ceramics and copper foil has high bonding strength. If the copper foil has not been pre-oxidized, the wettability of CuOy will be poor, and a large number of voids and defects will remain at the bonding interface, which will lower the bonding temperature and thermal conductivity. . For the preparation of DBC substrates using AIN ceramics, the ceramic substrate needs to be pre-vaporized to first form an A202 film, and then react with the AIN foil for eutectic reaction. l Advantages: Since copper foil has good electrical and thermal conductivity, and alumina can effectively control the expansion of the Cu-Al2 O₂-Cu composite, the DBC substrate has a thermal expansion coefficient similar to that of silver oxide, so DBC has good thermal conductivity and insulation Strong performance and high reliability. The process flow is relatively simple and the cost is low l Disadvantages: (1) The preparation process utilizes the eutectic reaction between Cu and A202 at high temperature (1065°C), which requires high equipment and process control, making the substrate cost relatively high;(2) Since micropores are easily generated between the Al20 and Cu layers, the thermal shock resistance of the product is reduced. These shortcomings have become a bottleneck in the promotion of DBC substrates.(3) It can only produce single panels and cannot be used for through-hole conduction applications: it has been widely used in IGBT, LD and CPV packaging, consumer and low-end refrigeration chip markets. Especially because the copper foil is thick (100~600μm), it has obvious advantages in the field of IGBT and LD packaging. l Application: It has been widely used in IGBT, LD and CPV packaging, consumer and low-end refrigeration chip markets. Especially because the copper foil is thick (100~600μm), it has obvious advantages in the field of IGBT and LD packaging  

In the field of electronics manufacturing, IPC Level 2 represents the standard for producing reliable electronic products with good quality levels, while IPC Level 3 represents a more stringent standard specifically for mission-critical applications where failures can have catastrophic consequences and the highest levels of quality and reliability are required; In essence, Level 2 is considered "normal" quality, while Level 3 is suitable for highly sensitive applications such as military or medical equipment. IPC Level 2 products, i.e., dedicated service electronic products, include communications equipment, complex industrial and commercial equipment, and high-performance, long-life measuring instruments. The IPC Level 2 standard specifies that such products should not fail under general use environments. IPC Level 3 products, i.e., high-performance electronic products, include highly reliable, long-life military and civilian equipment that can operate continuously. Such products are absolutely not allowed to have interruption failures during use, and at the same time, reliable startup and operation of the equipment must be ensured in harsh environments. For example, medical life-saving equipment and all military equipment systems.Comparison ParametersIPC Level 2IPC Level 3Average copper thickness20um20umMinimum copper thickness18um20umCopper plating voidsl The number of cavities in the hole is no more than 1l The number of holes containing cavities is no more than 5%.l The length of the cavities is no more than 5% of the hole lengthl The circularity of the cavities is no more than 90 degreesl There is no more than 1 cavity in the hole,l The number of holes containing cavities does not exceed 5%,l The length of the cavity does not exceed 5% of the hole length,l The loop length of the cavity does not exceed 90 degreesGeneral rules for surface coatingl The overlap area of  exposed copper/plating is no more than 1.25mml The overlap area of  exposed copper/plating is no more than 1.25mmEtching logol Line width of legible characters can be reduced to 50%l The line edges of characters may be slightly irregularSilk screen or ink stamping logol As long as the characters are clear, the ink can be accumulated outside the character lines.l As long as the required orientation is still clear, the outline of the component orientation symbol can be partially removed.l The marking ink of the component hole pad shall not penetrate into the component mounting hole or cause the ring width to be less than the minimum ring width.l As long as the characters are clear, ink can accumulate outside the character linesStraw-type gapl Straw-like gaps appear along the side edges of the conductive pattern. The reduction in the wire spacing caused by the straw-like gaps has not yet fallen below the minimum specified requirement, and the straw-like gaps have not yet extended to the entire edge of the conductive pattern.l No straw gapWire spacingl Any combination of defects such as rough copper spikes on the edge of the conductor causes the reduction of the conductor spacing in an isolated area to be no greater than 30% of the minimum conductor spacing.l Any combination of defects such as rough copper thorns on the edge of the conductor causes the reduction of the conductor spacing in the isolated area to be no more than 20% of the minimum conductor spacing.Outer ring width of support holel The loop is not greater than 90 degrees and meets the minimum lateral spacing requirements.l If the reduction in the wire width at the connection area between the pad and the wire is not greater than 20% of the nominal minimum wire width in the engineering drawing or production base, a loop is allowed to be broken by 90 degrees. The wire connection should be no less than 0.05mm or the minimum line width, whichever is smaller.l The hole is not located in the center of the pad, but the ring width is not less than 0.05mm (0.0020in)l The ring width in the isolated area is allowed to be reduced by 20% due to defects such as pits, pits, notches, pinholes or oblique holes.Annular width of unsupported holel The hole ring width is not broken.l The ring width in any direction shall not be less than 0.15 mm (0.00591 in). For the hole ring in the oblique area, due to the presence of pits, pits, notches, pinholes or oblique holes, the minimum outer ring width is allowed to be reduced by 20%.Negative Etchbackl Negative etch less than 0.025mml Negative etch is less than 0.013mmInner ring widthl The ring is not more than 90 degreesl The minimum ring width is not less than 0.025mmWickingl Wicking effect is no greater than 0.10mm (0.0040in).l Wicking effect is no greater than 0.08mmWicking effect of isolation holesl Wicking effect is no greater than 0.10mm (0.0040in).l Wicking effect is no greater than 0.08mmCovering layer coveragel There are weldable holes within at least 270 degrees of the circumferencel The minimum weldable annular ring width around the entire circumference is 0.13mm (0.00512in).Overlap of clearance holes between cover and reinforcement platel There is a weldable annular ring over at least 270 degrees of the circumference.l The minimum weldable hole ring width on the entire circumference is 0.13mm.l For non-supported holes, the weldable hole ring width is not less than 0.25mm.Connection between metal core and plated hole walll The separation at the interconnection should not exceed 20% of the thickness of the metal core. If a copper-clad metal core is used, there should be no separation at the copper interconnection.l No separation at interconnection 

In the field of electronics manufacturing, IPC Level 2 represents the standard for producing reliable electronic products with good quality levels, while IPC Level 3 represents a more stringent standard specifically for mission-critical applications where failures can have catastrophic consequences and the highest levels of quality and reliability are required; In essence, Level 2 is considered "normal" quality, while Level 3 is suitable for highly sensitive applications such as military or medical equipment. IPC Level 2 products, i.e., dedicated service electronic products, include communications equipment, complex industrial and commercial equipment, and high-performance, long-life measuring instruments. The IPC Level 2 standard specifies that such products should not fail under general use environments. IPC Level 3 products, i.e., high-performance electronic products, include highly reliable, long-life military and civilian equipment that can operate continuously. Such products are absolutely not allowed to have interruption failures during use, and at the same time, reliable startup and operation of the equipment must be ensured in harsh environments. For example, medical life-saving equipment and all military equipment systems.Comparison ParametersIPC Level 2IPC Level 3Average copper thickness20um20umMinimum copper thickness18um20umCopper plating voidsl The number of cavities in the hole is no more than 1l The number of holes containing cavities is no more than 5%.l The length of the cavities is no more than 5% of the hole lengthl The circularity of the cavities is no more than 90 degreesl There is no more than 1 cavity in the hole,l The number of holes containing cavities does not exceed 5%,l The length of the cavity does not exceed 5% of the hole length,l The loop length of the cavity does not exceed 90 degreesGeneral rules for surface coatingl The overlap area of  exposed copper/plating is no more than 1.25mml The overlap area of  exposed copper/plating is no more than 1.25mmEtching logol Line width of legible characters can be reduced to 50%l The line edges of characters may be slightly irregularSilk screen or ink stamping logol As long as the characters are clear, the ink can be accumulated outside the character lines.l As long as the required orientation is still clear, the outline of the component orientation symbol can be partially removed.l The marking ink of the component hole pad shall not penetrate into the component mounting hole or cause the ring width to be less than the minimum ring width.l As long as the characters are clear, ink can accumulate outside the character linesStraw-type gapl Straw-like gaps appear along the side edges of the conductive pattern. The reduction in the wire spacing caused by the straw-like gaps has not yet fallen below the minimum specified requirement, and the straw-like gaps have not yet extended to the entire edge of the conductive pattern.l No straw gapWire spacingl Any combination of defects such as rough copper spikes on the edge of the conductor causes the reduction of the conductor spacing in an isolated area to be no greater than 30% of the minimum conductor spacing.l Any combination of defects such as rough copper thorns on the edge of the conductor causes the reduction of the conductor spacing in the isolated area to be no more than 20% of the minimum conductor spacing.Outer ring width of support holel The loop is not greater than 90 degrees and meets the minimum lateral spacing requirements.l If the reduction in the wire width at the connection area between the pad and the wire is not greater than 20% of the nominal minimum wire width in the engineering drawing or production base, a loop is allowed to be broken by 90 degrees. The wire connection should be no less than 0.05mm or the minimum line width, whichever is smaller.l The hole is not located in the center of the pad, but the ring width is not less than 0.05mm (0.0020in)l The ring width in the isolated area is allowed to be reduced by 20% due to defects such as pits, pits, notches, pinholes or oblique holes.Annular width of unsupported holel The hole ring width is not broken.l The ring width in any direction shall not be less than 0.15 mm (0.00591 in). For the hole ring in the oblique area, due to the presence of pits, pits, notches, pinholes or oblique holes, the minimum outer ring width is allowed to be reduced by 20%.Negative Etchbackl Negative etch less than 0.025mml Negative etch is less than 0.013mmInner ring widthl The ring is not more than 90 degreesl The minimum ring width is not less than 0.025mmWickingl Wicking effect is no greater than 0.10mm (0.0040in).l Wicking effect is no greater than 0.08mmWicking effect of isolation holesl Wicking effect is no greater than 0.10mm (0.0040in).l Wicking effect is no greater than 0.08mmCovering layer coveragel There are weldable holes within at least 270 degrees of the circumferencel The minimum weldable annular ring width around the entire circumference is 0.13mm (0.00512in).Overlap of clearance holes between cover and reinforcement platel There is a weldable annular ring over at least 270 degrees of the circumference.l The minimum weldable hole ring width on the entire circumference is 0.13mm.l For non-supported holes, the weldable hole ring width is not less than 0.25mm.Connection between metal core and plated hole walll The separation at the interconnection should not exceed 20% of the thickness of the metal core. If a copper-clad metal core is used, there should be no separation at the copper interconnection.l No separation at interconnection 

 As surface mount technology (SMT) becomes the mainstay of the electronics industry, printed circuit boards (PCBs) are moving away from traditional organic laminates as substrate materials to materials with extremely high reliability, density, and precision. This requirement comes from the need to make electronic products thinner, smaller, and more functional than before.PCB ceramics, as a new type of circuit material, have received great attention from the industry. In addition to being very effective in providing solutions for the miniaturization of modern electronic products, ceramic PCBs also have many excellent functional properties that make them suitable for many fields, including LED lighting, semiconductor coolers, high-power semiconductor modules, power control circuits, electronic heaters, smart power devices, power hybrid circuits, high-frequency switching power supplies, automotive electronics, solid-state relays, military electronics, aerospace, communications, etc.The high thermal conductivity of ceramic PCBs is the main reason why the industry prefers to use them. FR-4 PCBs usually require heat dissipation vias, inner metal planes, heat dissipation platforms, and active cooling devices such as fans to take heat away from hot components. Ceramic PCBs do not require any of these components except in extreme cases, because PCBs can easily transfer heat to active cooling components, thermal landings, or device packaging.While thermally conductive materials are also generally good electrical conductors, ceramic materials are different in that their electrical conductivity is low enough for manufacturers to use them as PCB substrates. In addition, manufacturers use doping to adjust the conductivity of ceramic boards.Other advantages of low thermal expansion coefficient and high surface hardness increase the appeal of ceramic materials. Although ceramic PCBs are more expensive than boards made from traditional materials, the benefits of ceramic PCBs far outweigh the extra expense. Most industries prefer to use these expensive ceramic boards more out of necessity.  Ceramic PCB Technology  Ceramic PC8s primarily use a metal core. There is no single type of ceramic material. The term refers to a class of materials with similar physical properties and chemical structures. Aluminum nitride boards offer the highest thermal conductivity, but the material is expensive. Aluminum oxide boards are cheaper, but have lower thermal conductivity. However, ceramic PCBs have significantly better thermal performance than conventional metal core printed circuit boards because they do not require an electrical insulation layer between the core and the circuit traces.Manufacturers also offer other choices for the metal substrate of ceramic PCBs, such as nitride, oxide, and silicon carbide. Although many manufacturers offer copper or gold, silver is the common material for connecting traces on each layer. Manufacturers use a layer-by-layer screen printing process to place metal components or substrates.The bonding between ceramic and metal foil is high, and the surface flatness is high. Manufacturers use medium or low-power F CO2 lasers to drill through holes with high precision, high speed, and high efficiency. After transferring the circuit pattern to the gold foil using photolithography, manufacturers pre-plate a layer of lead-tin resist on the pattern and chemically etch away the unprotected parts to form the circuit. Removing the tin-lead layer requires cleaning with a nitric acid solution.After printing and stacking the ceramic layers, the manufacturer fires the entire stack in an oven, and the firing temperature for baking ceramic boards is usually less than 1000C. The lower firing temperature matches the sintering temperature of metal traces, which makes the low-temperature baking process suitable for using gold/silver as metal traces on ceramic PCBs.Unlike traditional circuit boards, ceramic PCBs do not use OSP, HASL or any other traditional surface finish. However, if there is a possibility of silver corrosion, gold can be plated on the exposed pads.    Ceramic pcb vs mcpcb  The advantage of ceramic substrates over metal substrates is that they have good thermal conductivity, heat dissipation and insulation. Ceramic substrates are inorganic substrates, while metal substrates are organic substrates, with different thermal conductivities; the thermal conductivity of metal substrates is less than 5W, while that of ceramic substrates is 30~180W, which is a huge difference; therefore, ceramic substrates have better thermal conductivity than metal substrates. Ceramic substrates have better insulation than metal substrates. Ceramic substrates are insulated by themselves, and no insulation layer is required, and the insulation effect is good. Ceramic substrates have better thermal conductivity, heat dissipation and insulation performance than metal substrates. Aluminum oxide (Al2O3) is widely used because of its low cost. However, it is a less good thermal conductor (24-28 W/mK), but is still better than most IMS (metal core) PCBs because it does not require a dielectric layer between the circuit and the core. If necessary, silver (Ag)-filled through-holes can still improve thermal performance. The board is usually thicker (0.5mm-1.5mm). Aluminum oxide can also be made transparent, click here for more information on transparent PCBs.Aluminum Nitride (AlN) has better thermal performance (>170 W/mK), but is also more expensive. Additionally, Ag or Au traces and vias can further improve thermal performance.Circuits can be printed using either copper (Cu) or silver (Ag), depending on the application and requirements. Copper is available with both DBC/DPC as well as thick film screen printing processes, while silver is only available with the second manufacturing option. We recommend using copper in 1-2 layer applications from low to high volume applications. Silver is recommended when doing multiple layers and only for medium to high volumes due to the higher tooling costs. If you are unsure of what material to specify, please feel free to contact us.When using copper metallization, solder mask and surface finish can be used similarly to normal PCBs. However, for silver thick film designs, we only offer glass solder mask, which is recommended for high temperature designs. For high sulfur environments where silver corrosion can be an issue, we offer gold plating as a solution to protect exposed pads.Due to its dielectric and thermal conductive properties, components can be placed directly on ceramic boards, and heat can flow through them more easily compared to FR4 and metal core boards. Furthermore, since (buried) vias are possible, multilayer boards can also be made into ceramic PCBs, becoming a real alternative to FR4/CEM3 and metal core PCBs.For a complete comparison with FR4/CEM3 and metal core boards, we refer to the table below.