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How to Make Ceramic PCBs: 5 Ceramic PCB Manufacturing Processes

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Wed, Jul 14, 2021

ceramic PCB

Ceramic PCBs are composed of a ceramic substrate, a connection layer, and a circuit layer. Unlike MCPCB, ceramic PCBs do not have an insulation layer, and manufacturing the circuit layer on the ceramic substrate is difficult. How are ceramic PCBs manufactured? Since the ceramic materials were used as PCB substrates, quite a few methods were developed to manufacture the circuit layer on a ceramic substrate. These methods are HTCC, DBC, thick film, LTCC, thin-film, and DPC. (in chronology)

HTCC

  • Pros: high structural strength; high thermal conductivity; good chemical stability; high wiring density; RoHS certified
  • Cons: poor circuit conductivity; high sintering temperatures; expensive cost

HTCC is an abbreviation of high-temperature co-fired ceramic. It is the earliest ceramic PCB manufacturing method. The ceramic materials for HTCC are alumina, mullite, or aluminum nitride. Its manufacturing process is:

  • At 1300-1600℃, ceramic powder (without glass added) is sintered and dried to solidify. If the design requires through holes, holes are drilled on the substrate board.
  • At the same high temperatures, high-melting-temperature metal is melted as a metal paste. The metal can be tungsten, molybdenum, molybdenum, manganese, and so on. The metal can be tungsten, molybdenum, molybdenum, and manganese. The metal paste is printed according to the design to form a circuit layer on the circuit substrate.
  • Next, 4%-8% sintering aid is added.
  • If the PCB is multilayer, layers are laminated.
  • Then at 1500-1600℃, the whole combination is sintered to form the ceramic circuit boards.
  • Finally, the solder mask is added to protect the circuit layer.

Summary: As the HTCC technology requires high temperatures, copper, silver, and gold can't be used for the circuit layer. The high-melting-point circuit metal has poor circuit conductivity. This leads to signal delay. So ceramic circuit boards made by the HTCC technology can't be used for high-speed and high-frequency circuits.

Instead, due to the features of high thermal conductivity and structure strength, HTCC ceramic PCBs are suitable for high-power circuits.

DBC

  • Pros: high thermal conductivity; high adhesion strength; excellent solderability; cheaper
  • Cons: no through-holes; poor precision; rough surface; only applied to big-line-with design; only suitable for batch production

DBC is the abbreviation of direct bonded copper. It was invented in 1975. The copper-clad (thickness > 0.1mm) is directly bonded onto the ceramic substrate at high temperatures. The ceramic materials for DBC technology are alumina and aluminum nitride. Its manufacturing process is:

  • In the N₂atmosphere, the copper plate is directly bonded to the ceramic substrate at 1065-1083℃.
  • Then the circuit layer is etched on the copper-clad.
  • If the PCB is multilayer, layers are laminated.
  • Finally, a solder mask is added to protect the circuit.

Summary: During the ceramic PCB manufacturing process, there may be small bubbles between the ceramic substrate surface and the copper circuit layer. For this reason, the product not-good rate is high. And this technology doesn't allow through-holes to be drilled. If the design requires through-holes, ceramic PCB manufacturing has to adopt other methods.

However, DBC may be the cheapest and quickest ceramic PCB manufacturing method for batch production. And there is no conspicuous connection layer between the ceramic substrate and the circuit layer, so the thermal dissipation is better.

Besides, the copper circuit layer has a high current-carrying capacity. A DBC ceramic PCB can reduce the module size and increase the power capacity. Due to these features, DBC ceramic PCBs are mainly used for packaging applications such as power electronic modules, semiconductor refrigeration, and LED devices.

Thick Film Ceramic PCB Manufacturing

  • Pros: good mechanical strength; good surface flatness; high stability; RoHS certified
  • Cons: can't manufacture three-dimensional circuits; can't manufacture fine circuits; poor electrical conductivity

Unlike the above two ceramic PCB manufacturing methods, the thick film technology manufactures resistors while PCB manufacturing. The ceramic materials for the thick film ceramic manufacturing are 96%/85% alumina (96% at PCBONLINE) and aluminum nitride. Its manufacturing process is:

  • First, a circuit diagram is divided into many functional parts, and the parts are transferred into the planar circuit image on the ceramic substrate.
  • The copper circuit layer has an extremely high current-carrying capability;
  • Then a thick film circuit template is manufactured using the photoengraving method.
  • At the same time, the thick film paste is prepared. The paste is manufactured by mixing fine metal (gold, platinum, copper, nickel, aluminum, or their alloy) powder, ceramic powder, and organic binder.
  • Next, the thick film paste is printed onto the ceramic substrate using screen-printing technology.
  • Then the thick film paste and the ceramic substrate are sintered to a whole at about 1000℃.
  • During sintering, the organic binder decomposes and volatilizes, and the resistors also form.
  • The resistors are trimmed by laser to the required resistance.
  • Finally, a solder mask is added to protect the circuit.

Summary: The thick film technology can print the circuit in high precision on the ceramic substrate. But the circuit minimum line space of thick film ceramic PCBs is at least 60μm. So if the design has a line width smaller than 60μm, the circuit boards can be manufactured by the thick film method.

Besides, the circuit layer has poor electrical conductivity because of its ceramic/glass properties. For this reason, thick film ceramic PCBs are manufactured for devices that have lower requirements for power and size.

LTCC

  • Pros: high electrical conductivity; low dielectric loss; resistors can be printed during manufacturing; low sintering temperatures; manufacturing and assembly done together at one time
  • Cons: unmatched contraction problems; thermal dissipation problems; lower thermal dissipation

LTCC is the abbreviation low temperature co-fired ceramic. It was invented in 1982. The ceramic substrate, components, and electrode materials are assembled when manufacturing. LTCC ceramic PCBs are usually multilayer and in three-dimensional design. The substrate materials for LTCC ceramic PCBs are glass bonded ceramics, ceramic-glass composite, and glass ceramics. Its manufacturing process is:

  • At lower temperatures, ceramic powder is sintered to be a dense raw ceramic substrate of precise thicknesses.
  • Next, the raw ceramic substrate is drilled by laser.
  • Then, liquid copper is injected into the vias, and precision conductive paste is printed to form the circuit layer.
  • Passive components are placed between the multiple circuit layers, and then the circuit layers are laminated.
  • At about 900℃, the whole structure is sintered to form a three-dimensional circuit board.
  • Then solder mask is added to protect the circuit.

Summary: on the surface of the LTCC ceramic circuit board, ICs and active components can be assembled. In this way, LTCC ceramic PCBs can be manufactured to be passive/active integrated functional modules. The functional module can further miniaturize and increase the density. So LTCC ceramic PCBs are especially suitable for high-frequency communication devices.

Thin Film Ceramic PCB Manufacturing

  • Pros: lower manufacturing temperature; fine circuit; good surface flatness
  • Cons: expensive manufacturing equipment; can't manufacture three-dimensional circuits

The copper layer on the thin film ceramic PCBs has thicknesses smaller than 1mm. The main ceramic materials for thin-film ceramic PCBs are alumina and aluminum nitride. Its manufacturing process is:

  • The ceramic substrate is cleaned first.
  • In vacuum conditions, moisture on the ceramic substrate is thermally evaporated.
  • Next, a copper layer is formed on the ceramic substrate surface by magnetron sputtering.
  • The circuit image is formed on the copper layer by yellow-light photoresist technology.
  • Then the excessive copper is removed by etching.
  • Finally, the solder mask is added to protect the circuit.

Summary: the thin film ceramic PCB manufacturing is finished in vacuum condition. The yellow light lithography technology allows more precision to the circuit. However, thin-film manufacturing has a limit to copper thickness. Thin-film ceramic PCBs are suitable for high-precision packaging and devices in a smaller size.

DPC

  • Pros: no limit to the ceramic type and thickness; fine circuit; lower manufacturing temperature; good surface flatness
  • Cons: expensive manufacturing equipment

DPC is the abbreviation of ceramic plated copper. It develops from the thin film ceramic manufacturing method and improves by adding the copper thickness through plating. Its manufacturing process is:

  • The same manufacturing process of the thin-film manufacturing until the circuit image is printed on the copper film.
  • The circuit copper thickness is added by plating.
  • The copper film is removed.
  • Finally, the solder mask is added to protect the circuit.

    3D DPC

Summary: DPC ceramic manufacturing can be planar or three-dimensional. PCBONLINE adopts the 3D DPC technology for ceramic PCB manufacturing.

DPC technology is appropriate for the manufacturing of most ceramic PCBs. Like thin-film ceramic PCBs, the lines are fine, and the circuit has high precision. 3D DPC ceramic PCBs are usually used for three-dimensional hermetic packaging of high-power LEDs. Especially, the aluminum nitride DPC ceramic PCBs can be used for SiC/GaN-based optoelectronics and semiconductor power devices, optical fiber communications, 5G radio frequency modules, high-power microwave modules, photovoltaic modules, and MEMS sensors.

PCBONLINE: High-Quality Ceramic PCB Manufacturer

PCBONLINE, one of the leading ceramic PCB manufacturers, mainly adopts the 3D-DPC technology for ceramic PCB manufacturing. But it can also use the other manufacturing technology according to clients' requirements. PCBONLINE provides one-stop ceramic PCB manufacturing, PCB assembly, and products, including alumina PCBs, aluminum nitride PCBs, SiC PCBs, IGBT modules, COB LED modules, DOB LED modules, etc.

Here are some reasons to choose PCBONLINE as your one-stop ceramic PCB manufacturer:

  • The thickness of the circuit layer is arbitrarily customized from 1μm to 1mm.
  • Three-dimensional design can be achieved.
  • Ceramic PCBs can be manufactured to be high-density (20μm minimum line space).
  • A better welding performance and temperature resistance.
  • The circuit layer doesn't contain an oxide layer and has a longer shelf life.
  • PCBONLINE provides free one-on-one engineering support (DFX).

PCBONLINE provides online and emails quotation methods. Register online, and you will get $100 coupons for online purchases.

Conclusion

This article lists the common ceramic PCB manufacturing methods. It introduces the ceramic PCB manufacturing processes and gives a brief analysis of the methods. If engineers/solutions companies/institutes want to have ceramic PCBs manufactured and assembled, PCBONLINE will bring 100% satisfying results to them.