The Ultimate Guide to Ceramic PCBs

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Nov 4, 2019|Technological Advancements and Materials

Ceramic circuit boards offer a host of benefits over traditional printed circuit boards (PCBs). Due to its high thermal conductivity and minimal expansion coefficient (CTE), ceramic circuit boards are more versatile, less complex, and offer superior performance compared to regular PCBs.

Want to find out more about ceramic PCBs and how they can make a positive addition to your company’s overall system costs? In this article, we cover everything there is to know about ceramic PCBs, the various types available, and their respective use cases.

Pros & Cons of Ceramic PCBs

Pros:

• Excellent thermal conductivity
• Resists chemical erosion
• Compatible mechanical intensity
• Easy high-density tracing implementation
• CTA component compatibility

Cons:

• Higher cost than standard PCBs
• Lower availability
• Fragile handling

Types of Ceramic PCBs

High Temperature

Perhaps the most popular type of ceramic PCB is the high-temperature PCB. Ceramic circuit boards designed for high temperatures are often referred to as High-Temperature Co-fired Ceramic (HTCC) circuits. These circuits are constructed by mixing adhesive, lubricant, solvent, plasticizer, and aluminum oxide to create raw ceramics.

With the raw ceramic material produced, the material is then coated, and circuit tracing is implemented on tungsten or molybdenum metals. Once implemented, the circuits are baked between 1600 and 1700 degrees Celsius for up to 48 hours after lamination. All HTCC baking is done in a gaseous environment, such as in hydrogen gas.

Low Temperature

Unlike HTCCs, low-temperature co-fired ceramic PCBs are produced by combining crystal glass with an adhesive substance on sheet metal with gold paste. Then, the circuit is cut and laminated before placed in a gaseous oven at roughly 900 degrees Celsius.

Low-temperature co-fired ceramic PCBs benefit from less warpage and improved shrink tolerance. In other words, they have a superior mechanical intensity and thermal conductivity compared to HTCCs and other types of ceramic PCBs. The thermal benefit of LTCCs provides an advantage when working with heat-emitting products, like LED lights.

Thick Film Ceramic

Thick film ceramic circuits involve gold and dielectric pastes that are implemented on a ceramic base material. Once implemented, the pastes and baked at a temperature of 1000 degrees Celsius or below. This variety of PCB is popular among major printed circuit board manufacturers due to the high cost of gold conductor paste.

The main benefit of thick film ceramic material over traditional PCBs is that thick film ceramic prevents copper from oxidizing. Therefore, a ceramic PCB manufacturer can benefit from choosing thick-film ceramic circuits if they are concerned about oxidation.

We’re often asked, “how many layers is a ceramic PCB?” However, the answer depends on the type of ceramic PCB used. The minimum number of layers utilized in a ceramic PCB is two, but there may be several more depending on the product’s properties. A trace width calculator can help manufacturers understand the specifications of their PCB design.

Use Cases for Ceramic PCBs

Memory Modules

One of the key application fields of ceramic PCBs has to do with memory modules. These PCBs have memory integrated circuits that are commonly used in the production of DDR SDRAM and other computer components related to memory. All RAM used in personal computers requires ceramic substrate PCBs with integrated memory modules.

Receiving & Transmission Modules

The production of radar technology is made possible by ceramic PCBs. The American firm Westinghouse was the first to create transmission and receiving modules using multi-layer ceramic PCBs due to their high thermal conductivity and compatible CTE. Unlike regular PCBs, ceramic circuits are the only kind that are useful in the creation of transmission modules.

Multilayer Interconnect Board

One of the key selling points of ceramic PCBs is that they have a greater capacity than regular circuit boards. In other words, ceramic PCBs can hold more components using the same amount of surface area than a conventional PCB. Therefore, ceramic PCBs have a greater number of potential applications using a multi-layer interconnect board.

Analog/Digital PCB

Various computing firms have used low-temperature ceramic circuit (LTCC) boards to create superior analog and digital boards with superior circuit tracing. Personal computer companies have utilized LTCCs to create a host of lightweight circuits that reduce the total weight of the product and minimize crosstalk interference.

Solar Panels

HTCCs and LTCCs alike are used in the manufacturing of solar panels and other photovoltaic (PV) electrical panels. PV panels utilize multilayered ceramic board technology to ensure longevity and adequate thermal conductivity.

Electric Power Transmitter

Wireless power transfer and charging modules are becoming increasingly common consumer electronics devices. These devices are constructed using ceramic PCB technology because of their unique thermal properties and heat-dissipation ceramic substrate.

Ceramic circuit boards are used to create an electromagnetic field with which to transfer energy between a receiver and a transmitter. Induction coils facilitate the transfer of electricity from the original electromagnetic field and convert it into an electrical current for the receiver circuit. Often, the receiver circuit is made of ceramic-based PCB materials.

Semiconductor Cooler

More and more electronic devices are becoming miniaturized. Behind the miniaturization of consumer electronics are semiconductor chips, which are getting smaller and smaller every year. Semiconductor chips use micro-fabrication technology to allow for higher integration at high speeds while maintaining optimal tracing capabilities.

Traditional PCBs cannot facilitate the number of circuit functions required of modern-day semiconductor chips. However, the advent of ceramic-based semiconductor circuits has led to superior integration and performance among miniature circuit assembly. Therefore, ceramic PCB substrates are often considered the future of semiconductor technology

High Power LED

Ceramic substrates provide an optimal submount for high power LED lights. Unlike conventional PCBs, ceramic circuits use thick film technology to maximize thermal efficiency. The result is that the heat produced by the LED light (LEDs are roughly 70% heat) does not impact the circuit operational efficiency.

In other words, only ceramic circuits offer the level of thermal efficiency required for LED light production. When LEDs are built on ceramic circuits, thermal interface materials, also known as heat sinks, are not required. Therefore, there are fewer materials needed to produce and maintain LED light if the manufacturer uses ceramic circuitry.

Manufacturing Process of Ceramic PCBs

Step 1: The Design

The unique design of your ceramic PCB is the beginning of the manufacturing process. You can use design software to create the exact model that you need or use a trace width calculator to help you come up with the details for the inner and outer layers.

Step 2: Printing the Design

Print the design of your PCB on the board using a plotter printer. The printer will produce a film that provides layer details.

Step 3: Creating the Substrate

The substrate will then pass through an oven for the semi-curing process. This allows copper to pre-bind to both sides of the layer. Then, this layer will be etched away to reveal the printed design of the films.

Step 4: Printing of inner layers

A photo-sensitive film is then mounted to the board. As this is bathed in ultraviolet light, it will harden and the blueprints will be aligned with the actual print of the board.

Step 5: Ultraviolet Light

Bathe the board in ultraviolet light after aligning the resist and the laminate. This will harden the photoresist. The board is then washed in an alkaline solution that cleans it of any unwanted copper.

Step 6: Layer-up and Bond

The layers enter the fusion stage, where the out layers are joined with the substrate. The layer and bonding steps require metal clamps and a steel table, where the layers are securely fitted into pins attached to the table. Ensure they fit appropriately so they do not shift during alignment. Then, place the prepreg layer over the alignment resin. Before placing the copper sheet, fit the substrate layer over the prepreg layer. You can then fit more sheets of prepreg over the copper layer, where the aluminum foil and a copper press plate will complete the stack. This leads us to the pressing stage, where a press-bonding computer will heat the stack before it’s cooled down.

Step 7: Drill

With careful precision, you can drill holes into the stack board. The holes should be drilled to a hair’s width using an X-ray locator to identify the target spots. Before drilling begins, ensure you place bugger material beneath the drill target so that the enacted bore remains clean. The drill step is computer-aided with specific spindles that rotate at high speeds. This step can take some time depending on how many holes need to be drilled.

Step 8: Plating and Copper Deposition

Before this step begins, the inner surfaces are exposed to the substrate. Copper baths will then help cover the walls of the holes. This step fuses the various layers after the panel is thoroughly cleaned and washed in several chemical baths. The next chemical process will deposit a thin copper layer during the baths, about one micron thick. Copper is then filled into the drilled holes.

Step 9: Outer Layer Imaging

This step includes an additional application of photoresist on the panel. The prepped panel will pass beneath yellow lights that don’t carry UV levels, so the photoresists remain unaffected. The board is then secured to prevent misalignment with the panel. A generator will blast the panel and stencil with UV light as they come into contact. This will harden the photoresist, and you can then pass the panel through a machine that will remove the unhardened resist protected by black ink opacity. Any undesired photoresists should be removed from the outer plates.

Step 10: Plating

The board is then returned to the plating room, where the panel is electroplated with a thin layer of copper. The outer layer’s exposed sections from the photoresist stage will then receive copper electroplating. After these copper baths, the panel is then plated with tin. It is then possible to remove the copper remains left over from the etching stage.

Step 11: Final Etching

This stage protects the desired copper by removing any unwanted copper remaining below the resist layer. You can use various chemical solutions to clean away the excess copper, which protects the board.

Step 12: Solder Mask Application

The board must be rigorously cleaned before the solder mask is applied. Completely cover the board with epoxy solder, and then harden it with UV light. After the board is passed through solder mask ink, the covered portions will be ready for removal. The board is then passed through an oven which will cure the solder mask.

Step 13: Surface Finish

Chemically plate the board with gold or silver to add solderability to your ceramic PCB.

Step 14: Silkscreen

The board can be completed by indicating all the PCB innovations with ink-jet writing on the surface components. They pass the ceramic PCB to the final curing stage.

Step 15: Electrical Test

The functionality of the PCB will then be confirmed via the electrical test. This stage will also test how much the board has conformed to your original design.

Step 16: Profiling and V-Scoring

In this final step, you will cut different boards from the created panel. You can either use a router or a v-groove to pop out the boards from the panel and achieve your finished product.

Ceramic PCB Types

Alumina

Also known as Al2O3 and metal base PCB, Alumina is a PCB type that utilizes dielectric thermally conductive and electrically insulated material between the aluminum metal and the copper layer. It is the PCB of choice for anything that involves heat dissipation as well as overall temperature maintenance and control.

Aluminum constructions are usually made up of three layers.  A circuit layer made of copper around 1 to 10 oz. thick, an insulating layer made of thermally conductive and electrically insulated material, and a base layer made of copper or aluminum metal substrate.

Aluminum PCBs come in several types.  There’s the Flexible type, the Hybrid, the Multilayer, and the Through Hole types.

AIN

Also known as Aluminum Nitride, AIN is a new material that has been developed into a commercially viable product.  It comes with properties that are both reproducible and controlled within the last two decades.

AIN is an effective choice because of its good dielectric properties, low thermal expansion coefficient, high thermal conductivity, and its non-reactiveness with common semiconductor process chemicals, among others.

Aluminum Nitride PCBs are commonly used in heat sinks, microwave device packages, molten metal handling components, substrates for electronic packages,  and semiconductor processing chamber fixtures and insulators, just to name a few.

Ceramic PCBs FAQs

How Does a Ceramic PCB Differ From a Traditional PCB?

While ceramic PCBs are a relatively new creation, they have many advantages over traditional PCBs. Ceramic PCBs are more versatile and less complex while offering superior performance with higher thermal conductivity. Their minimal expansion coefficient (CTE) makes them appealing for many different technological applications.

Are Ceramic PCBs Fragile?

Ceramics insulate electricity well, but they are very brittle. This makes manufacturing complex and creates common issues such as their susceptibility to cracking during temperature changes or under mechanical stress. Since these PCBs are used in high-frequency electronics (such as medical devices and aerospace), they must be created with utmost care.

Why Is Thermal Conductivity Important in PCBs?

The innate thermal properties of printed circuit boards are a critical component for operating junction temperature. PCBs must be modeled as a single unit with two effective thermal conductivities to predict heat transfer. By establishing parallel thermal conductivity and normal thermal conductivity, the PCB can dissipate thermal power loss across the board. By optimizing the thermal characteristics of a component, you can ensure that the PCB avoids rising temperatures with the proper use of cooling measures.