Ceramic PCB Manufacturing
Ceramic printed circuits have a ceramic-based material as a substrate where an electronic circuit is ‘printed’ on. There are several material being used today with the below being most common:
- Alumina (Al2O3) PCB is the most common used material one
- Aluminum Nitride (AlN) circuits are probably a close second.
- BeO is being used less and less due to health & safety concerns
- Silicon Nitride based circuits are gaining importance
Contrary to ‘traditional’ PCBs there are a number of ways of how the circuit is made onto the ceramic with every manufacturing technology having its pros and cons. Here is a short overview of the different production technologies and their pros and cons.
DPC – direct plated copper:
Probably the closest method to standard circuits. A seed layer is sputtered onto a ceramic layer, which is then plated up to the necessary thickness.
More in detail, the build goes as follows.
First, there is an interface layer which usually not copper but which is VERY important.
Then a copper layer is applied. This seed layer is then plated up to the required thickness where traces and pads are using a mask.
Next, the seed layer is again etched away.
The rest of the process (Solder masks/legend) is similar to traditional circuits.
note that the solder masks used is also epoxy-based and very similar to standard PCB.
- Design can be similar to ‘standard’ PCB
- Copper thickness can be controlled
- Only for single & double-sided designs
- Limited max operating temperature
We offer DPC Ceramic PCB in with an Alumina and Aluminium Nitride substrate in both our C-Proto as well as our C-Production solution when you choose copper as conductor.
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The technology uses screen printing. A conductive ink layer is ‘printed’ and fired on a substrate at a temperature above 800C to create a strong bond and low resistance. This is followed by a dielectric ink or encapsulant (~soldermask) to make multilayers, cross overs, or to protect the circuits. As the firing temperature is much higher, thick film circuits can cope with much higher temperatures then DPC or other circuits. Thanks to the additive manufacturing processes, thick film allows for multilayer or 3D features like cavities or placement of components on different levels.
Next to conductive inks, also resistive inks can be printed to make resistors or heating elements. The main benefit of thick film is the additive element and the design freedom it has.
- single-sided, double-sided, multilayer, single-sided multilayer. multilayers on parts of the circuits, …. design possibilities are endless
- Many different conductive inks exist with each there own advantages (Ag, AgPd, AgPt, AgPdPt, Cu, Au,…)
- Resistors can be printed
- Strong environment protection (chemical hazards, UV degradation)
- capable of withstanding >350C operating temperatures
- Tooling is needed for high volume production (prototypes can be made without tools thanks to our C-proto solution)
At CERcuits, we offer Thick film Ceramic PCB in with an Alumina and Aluminium Nitride substrate in both our C-Proto as well as our C-Production solution. when you choose silver or silver-palladium metalization.
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Direct Bonded Copper (DBC)
Direct bonded copper metallization is made by bonding a sheet of copper onto a ceramic substrate using high temperature. The ceramic and copper layers are placed together and fired in a kiln under an inert atmosphere at high temperatures (typically around 1000°C). The heat causes the ceramic and copper to bond together, forming a monolithic structure that is strong and stable. The thickness of the copper layer can be varied depending on the desired performance and application.
- Direct bonding copper is usually preferred for thicker copper layers (200um, 300um or more which take a long time to make using direct plating copper (DPC). It is therefor used often used in high current, high voltage applications.
- Tracks and pads require relatively wide trackwidths and spacings.
- Not suitable for dense circuit layout or where small features are needed
- Hard to add solder masks
At CERcuits, we currently do not offer DBC circuit manufacturing in house. We have partners we work with and that can offer this. We can process DBC sheets, made by other companies into a circuit or submount for low volumes applications
Low Temperature Co-Fired Ceramic (LTCC)
Low temperature co-fired ceramics (LTCC) are made by bonding multiple layers of ceramic and metal together using a process called co-fired technology, which involves firing the layers in a kiln at relatively low temperatures (typically around 800-900°C). The ceramics are processed in the so-called ‘green’ state, which means they are typically formed using techniques such as pressing, casting, or extrusion, and they are then allowed to dry but not yet fired.
- One of the main advantages of LTCC is that it allows for the production of complex, multi-layered 3D shapes structures with a high degree of accuracy and precision. The layers of ceramic and metal can be precisely patterned and stacked to create a wide range packages and structures for many electronics components to be housed in.
- By changing the composition of the green state ceramics, the material can be tailored to meet demanding specifications in regards to RF and microwave properties (Dk / Loss tangent)
- Multilayered circuits can be made relatively easily with embedded signal layers, embedded passive printed elements or embedded heaters, sensors, …
- Even though LTCC circuits can reach higher thermal conductivities compared to standard circuit technology, the presence of a high glass frit content, needed to allow for green state processing, decreases the thermal conductivity a lot versus post fired metallization technologies like DPC or thick film printing
- Metallization is mostly done using silver based conductors that are printed, similar to (post-fired) thick film circuits which makes assembling prone to silver leaching issues or silver migration. Using silver-platinum or silver-palladium conductors can reduce the risk.
High temperature Co-fired Ceramic (HTCC)
The main difference between LTCC and HTCC is the firing temperature used in the co-fired process. LTCC is fired at relatively low temperatures (typically around 800-900°C), while HTCC is fired at higher temperatures (typically around 1000-1600°C).
As a result, HTCC has a higher density and mechanical strength than LTCC, and it is better suited for use in high-temperature or harsh environments applications making it an ideal choice for high-performance electronic devices.
HTCC also typically uses tungsten as a conductor in stead of silver or gold.