CVD Diamond PCBs & Substrates: Engineering Guide to Thermal Limits and Metallization

CVD Diamond PCBs: Solving Extreme Heat Flux in High-Power Electronics

When wide-bandgap (WBG) devices like GaN and SiC operate at elevated switching speeds and power densities, localized heat flux at the junction can easily exceed $1000\ W/cm^2$ . Standard aluminum oxide (

Al_2O_3

) and aluminum nitride (

AlN

) substrates struggle to dissipate this level of heat quickly enough to prevent thermal runaway.

CVD (Chemical Vapor Deposition) diamond substrates address this bottleneck directly. Because heat moves through diamond via lattice vibrations (phonons) rather than electron transport, it provides heat dissipation rates that metals and conventional ceramics cannot match.

1. Material Properties: Diamond vs. Standard Substrates

Property	FR-4	Copper Base (MCPCB)	Al2O3 (96%)	AlN	CVD Diamond
Thermal Conductivity ( $W/m\cdot K$ )	0.3	~390 (base only)	24 – 28	170 – 200	1000 – 2000
Coefficient of Thermal Expansion ( $ppm/K$ )	14 – 17	16.5	7.2	4.5	1.1 – 2.0
Dielectric Constant (1 MHz)	4.5	N/A	9.8	8.8	5.6
Dielectric Loss	0.02	N/A	0.0003	0.0005	< 0.0001
Breakdown Field ( $MV/cm$ )	0.2	N/A	0.15	0.2	10.0

Property

FR-4

Copper Base (MCPCB)

Al2O3 (96%)

AlN

CVD Diamond

Thermal Conductivity (

W/m\cdot K

)

0.3

~390 (base only)

24 – 28

170 – 200

1000 – 2000

Coefficient of Thermal Expansion (

ppm/K

)

14 – 17

16.5

7.2

4.5

1.1 – 2.0

Dielectric Constant (1 MHz)

4.5

N/A

9.8

8.8

5.6

Dielectric Loss

0.02

N/A

0.0003

0.0005

< 0.0001

Breakdown Field (

MV/cm

)

0.2

N/A

0.15

0.2

10.0

Key Takeaways for Hardware Designers

Thermal Spread: CVD diamond conducts heat 5 times faster than copper and roughly $8\times$ faster than $AlN$ , eliminating hot spots beneath active dies.

CTE Alignment: With a CTE around $1.5\ ppm/K$ , diamond closely tracks Silicon ( $2.6\ ppm/K$ ), $GaAs$ ( $5.7\ ppm/K$ ), and $GaN$ ( $3.2\ ppm/K$ . This close match prevents solder fatigue and micro-cracking across thousands of thermal shock cycles.

RF Performance: A low dielectric constant ( $\approx 5.6$ ) and near-zero dielectric loss make diamond suitable for high-frequency millimeter-wave (mmWave) trace routing without excessive signal drop.

2. Design & Cost Considerations

Is Full Diamond Necessary?

Solid CVD diamond substrates are reserved for extreme thermal bottlenecks. For broad-area boards where solid diamond is cost-prohibitive, two hybrid options are widely used:

Embedded Diamond Coins: Localized diamond inserts pressed or soldered directly beneath high-wattage components inside a traditional copper or ceramic baseboard.

Diamond-Copper Composites (Cu-Diamond MMC): A blend of diamond particles infiltrated with copper, delivering $500\text{–}600\ W/(m\cdot K)$ at a lower production cost.

If you are looking for a diamond substrate PCB, please contact us today to get a price or design suggestions!