What’s DBC (Direct Bonded Copper) in Ceramic PCB
DBC (Direct Bonded Copper) is a process in which copper and a ceramic substrate are directly bonded. DBC ceramic substrates have been proven for many years as an excellent solution for electrical isolation and thermal management of high power semiconductor modules. DBC ceramic substrate can also be the base material of Ceramic PCBs, but was replaced by the newest DPC (Direct Plated Copper) process. Because DPC has better electrical, thermal and mechanical performance.
The Structure of DBC Ceramic PCB
The DBC process yields a super-thin base and eliminates the need for the thick, heavy copper bases that were used prior to this process, so its structure also is very simple. A DBC ceramic circuit board is made of a layer of conductor (generally copper foil) and a ceramic substrate (they can be aluminum oxide (Al2O3), aluminum nitride (ALN) and zirconia (rarely to use)). The most common substrate thickness we use is 0.635mm.
ALUMINA PCB (96% & 99.6%)
Alumina Oxide (Al2O3) PCB (96% & 99.6%)
The most common material used for Ceramic PCBs is Alumina Oxide (96%). A naturally excellent electrical insulator with strong thermal properties. The thermal conductivity of Alumina is not as high as Aluminium Nitride, however it is still noticeably higher than the best performing Metal Clad PCB materials with a Thermal Conductivity in the region of 24W/mK. Another variant of this is Al2O3 (99.6%) which has a higher Thermal Conductivity, in the region of 29W/mK.
A high light reflectivity, along with good thermal properties makes Alumina Oxide well suited for LED applications. Whilst low values of thermal expansion and signal loss make it suitable for a range of applications including sensor modules, high-frequency systems and cooling systems.
Advantages
- High values of Thermal Conductivity (24-29W/mK)
- High substrate operating temperatures to over 800°C
- Low CTE
- Suitable for high frequency applications due to low signal loss
- High light reflectivity
- Possibility for Hermetic packages with 0% water absorption
ALUMINIUM NITRIDE PCB
Aluminium Nitride (AlN)
If a higher thermal conductivity is required then Aluminium Nitride (AlN) will be required. AlN has a superior thermal conductivity; depending on options, the conductivity achieved will be between 150-170W/mK.
This, along with a very low CTE and high operating temperatures makes AlN suitable for a variety of applications including; High power LEDs, testing, sensors, Integrated Components (ICs) and more.
Advantages
- Superior values of Thermal Conductivity (Up to 170W/mK)
- High substrate operating temperatures to over 800°C
- Very low CTE
- Suitable for high frequency applications due to low signal loss
- Possibility for Hermetic packages with 0% water absorption
SILICON NITRIDE PCB
Silicon Nitride (SiN)
| Property |
Unit |
SiN |
| Thermal Conductivity |
W/mK |
85 |
| Coefficient of Thermal Expansion (CTE) |
x 10¯6/K |
2.6 |
| Dielectric Constant |
– |
9 |
| Signal Loss |
x 10¯3 |
0.2 |
| Light Reflectivity |
% |
– |
| Breakdown Voltage |
KV/mm |
15 |
| Rupture Strength |
Mpa |
800 |
| Max Operating Temperature |
SiN |
| Substrate |
850° |
| Cu Conductor |
300° |
| Solder Resist |
100°C |
| Glass Resist |
500°C |
- Thermal Conductivity value between Al2O3 and AlN at 85-90W/mK run at extremely high temperatures, but in addition it has a
- High substrate operating temperatures to over 800°C
- Very low CTE
- High rupture strength – makes it a more attractive solution to harsher environments or environments with high levels of vibration.
- Suitable for high frequency applications due to low signal loss
- Possibility for Hermetic packages with 0% water absorption
Automotive DBC Ceramic PCB Stackup
DBC Ceramic PCB Stackup The DBC Ceramic PCB surface finishing is ENIG or ENIPIG. And the Copper from Min.5um up to 500um. DBC Ceramic PCB Ceramic material is Al2O3,Ain,BeO, and the ceramic pcb thickness is 0.25,0.381,0.5,0.635,1.0mm,1.5mm,2.0mm. Please see the bellow 1 Layer and 2 Layer DBC Ceramic PCB Stackup. 1 Layer DBC Ceramic PCB 2 Layers DBC Ceramic PCB
1 Layer DBC Ceramic PCB
2 Layers DBC Ceramic PCB
The main process of DBC ceramic PCB manufacturing
1. Preparation of the ceramic substrate
Cut the substrate material into the required size and shape, and any surface imperfections are removed. The most used substrates are aluminum oxide (Al2O3) or aluminum nitride (ALN), which are known for their excellent thermal conductivity and electrical insulation properties.
2. Deposition of copper
The next step involves depositing a thin layer of copper (usually less than 10 µm) on the ceramic substrate using various techniques such as electroless plating, sputtering, or evaporation. The thin layer of copper serves as a bonding layer for the thick copper layer that will be applied in the next step.
3. Bonding of copper
Once the thin layer of copper is deposited, the substrate is subjected to a high-temperature sintering process (usually at temperatures above 1000°C, it depends on the substrate we use), which causes the copper to bond with the ceramic substrate, forming a thick copper layer. The thickness of the copper layer is typically 100 µm to 200 µm, thicker of 300um also is available.
4. Etching of copper
Now the copper has been bonded to the ceramic substrate, at this step, we should remove the excess copper by etching process, leaving only the desired copper traces/circuits and pads. The etching process can be done using various techniques such as chemical etching or plasma etching.
5. Surface finishing
The final step involves finishing the DBC ceramic PCB by applying a protective coating or solder mask (but DBC ceramic PCB is rarely apply solder mask) to the copper circuits and pads. The protective coating helps to prevent oxidation and corrosion, which can degrade the performance of the PCB over time.
Benefits of DBC ceramic PCB
In fact, all the ceramic circuit boards feature a very good thermal conductivity and low CTE (coefficient thermal expansion) because the ceramic substrate itself has such properties. But ceramic board manufactured with different technology process has different advantages:
1. The thicker copper layer permits ceramic board has higher current loading for the same conductor width. Assuming the same copper cross-section the conductor needs to be only 12 % of that of a normal printed circuit board.
2. DCB ceramic PCB is gradually become the base materials of construction and interconnection technology of high-power semiconductor electronic circuits and also have been the basis for the “Chip-On-Board” (COB) technology which represent the packaging trend in the future.
3. Excellent electric insulation voltage means it can greatly improve the safety for the user.
4. Good thermal conductivity and heat-transfer provides the possibility of small packaging of the chips, result in increasing of power per unit of volume, improving reliability of systems and equipment.
5. The super-thin (0.25mm) DBC substrate can be an alternative material for beryllium oxide (BeO), it eliminates the unfriendly of environmental protection and toxicity; but seldom be used, as it is extreme expensive!
6. Superb thermal stability and power cycling capabilities (up to 50,000 cycles) makes it well-suited for applications that require in high temperature and high voltage environments, such as aerospace.
Where Can I Use the DBC ceramic PCB?
With the rapid development of the electronics and semi-conductors, there is no doubt that the era of big data is here. In the next couple years, DBC ceramic substrates will be sure to replace and serve as the fundamental materials for constructing and connecting electronic circuits, surpassing conventional printed circuit boards. These substrates will be utilized in electronic components with high power dissipation and stringent demands for thermal shock resistance and low failure rates, as showcased in the following examples:
A: Insulated Gate Bipolar Transistor (IGBT chips)
B: Power supply for telecommunication
C: Power semiconductor modules
D: High frequency switch mode power supplies (SMPS)
E: Solar cell component
F: Automotive system
G: Aerospace
DBC Ceramic PCB Manufacturing Capability from QFPCB
QFPCB has fabricated and supplied DBC ceramic board for many years, our full set of high-tech machines and a series of test equipment such for AOI, resistance measurement, two-dimensional testers support us to make high quality and defective-free products for our customers. Below are the manufacturing capabilities for DBC ceramic PCB:
| Item |
DCB/DBC Capabilities |
| Layer Count |
2 Layers |
| Max Board Dimension |
138*178mm |
| Min Board Thickness |
0.30mm.0.40mm |
| Max Board Thickness |
1L: 1.3mm; 2L 1.6mm |
| Conductor Thickness |
3.90Z-8.60z |
| Min Line Width/Line Space |
12/12mil (0.30/0.30mm) |
| Substrate Type |
AI203,ALN, Zro2 |
| Substrate Thickness |
0.25, 0.38, 0.50, 0.635, 0.76,1.0mm |
| Min Hole Diameter |
4mil (0.1mm) |
| Min Hole Spacing |
NPTH: 16mil (0.30mm); PTH: 20mil (0.5mm) |
| Min PAD Ring(Single) |
N/A |
| PTH Wall Thickness |
N/A |
| Min Solder PAD Dia |
8mil (0.20mm) |
| Min Soldermask Bridge |
8mil(0.20mm) |
| Min BAG PAD Margin |
8mil (0.20mm) |
| PTH/NPTH Dia Tolerance |
PTH: ±4mil (0.1mm) ; NPTH: ±2mil (0.05mm) |
| Hole Position Deviation |
± 4mil (0.1mm) |
| Outline Tolerance |
Laser: +0.2/0.05mm |
| Line Width/Spac Tolerance |
+5mil (0.125mm) |
| Surface Treatment |
OSP/Ni Plating, ENIG |
| Thermal Stress |
3 x 10 Sec @ 280C |
