Laser cutting of metal-ceramic substrates

Abstract

The present application relates to a method of laser ablation of a metal-ceramic substrate, in which a laser is used under process conditions in which the formation of solid metal particles on the metal-ceramic substrate, which can separate from metal particles released by laser ablation near the ablation edge, is essentially avoided. Further the present application relates to a ceramic-metal substrate comprising a ceramic substrate and a metallization on at least one side of the ceramic substrate, wherein the ceramic substrate and the metallization have flush cutting edge.

Claims

1. A method for ablation of a metal-ceramic substrate, comprising: ablating the metal-ceramic substrate with a laser; wherein the laser is used under process conditions such that less than 50% of the surface area near the ablation edge of the metal-ceramic substrate is covered with metal particles, wherein the area near the ablation edge has a width, calculated from the edge of the recess, of at most 200 μm; wherein the laser is used with a relationship between the laser power (W) and the effective maximal processing speed of the laser (m/sec) which corresponds to the following formula (1):
y≤4.7 ln x−15  (1) wherein x=laser power in W; y=effective maximal laser processing speed in m/sec; and wherein the laser power x is between 40 W and 200 W.

2. The method according to claim 1, wherein the laser is used with a relationship between the laser power (W) and the effective maximal processing speed of the laser (m/sec), which corresponds to the following formula (2):
y≤5.0 ln x−18  (2) wherein x=laser power in W; and y=effective maximal laser processing speed in m/sec.

3. The method according to claim 1, wherein the effective processing speed of the laser is at least 0.50 m/sec.

4. The method according to claim 1, wherein the metal is a copper layer or copper foil, which is applied onto a ceramic substrate.

5. The method according to claim 1, wherein the metal-ceramic substrate is a DCB substrate.

6. The method according to claim 1, wherein the laser is a p-sec laser having a pulse duration of 0.10 to 100.00 ps.

7. The method according to claim 6, wherein the p-sec laser has a pulse energy of 10.00 to 500.00 μJ.

8. The method according to claim 6, wherein the p-sec laser is an IR-P-sec laser.

Description

EXAMPLES

(1) The present invention is further explained by reference to the following examples which illustrate the present invention.

(2) Several DCB substrates are prepared according to a standard procedure known to the person skilled in the art. An Al.sub.2O.sub.3 ceramic is used as the substrate and a copper foil is used to prepare the metallic coating on the substrate.

(3) The Al.sub.2O.sub.3 ceramic substrate is used with a thickness of between 0.25 and 0.40 mm, whereas the metallic copper coating is used with a thickness of between 0.38 to 0.63 mm.

(4) The experiment are performed with the following set of parameters for the laser:

(5) Laser output power variable up to 100 W

(6) Laser source: IR

(7) Pulse length: 0.1 to 100 ps

(8) Pulse energy: 10 to 500 μJ

(9) Spot diameter 30 μm

(10) Frequency laser: 350 to 650 kHz

(11) In the experiments the metal (copper) on the ceramic substrate (Al.sub.2O.sub.3) is ablated.

(12) The resulting metal ceramic substrates are evaluated as follows:

(13) TABLE-US-00014 n.e. not economical +++ Very good appearance, almost no residues, very low roughness, almost no copper oxidation ++ Good appearance, slightly residues, low roughness, low copper oxidation + Appearance useable, visible residues, visible roughness, noticeable copper oxidation − Quality not acceptable, technically functionable, optical appearance bad extra Extrapolated Unusable Process limitation, not usable

(14) TABLE-US-00015 Laser speed Laser power (W) (m/sec) 30 40 50 60 70 80 90 100 120 150 0.25 +++ ++ + − − − − − 0.50 +++ ++ ++ + + − − 0.75 +++ ++ ++ ++ ++ + + − − 1.00 unusable +++ +++ +++ ++ ++ + + − 1.50 unusable +++ +++ +++ +++ ++ + 2.00 unusable +++ +++ +++ +++ ++ ++ extra 3.00 unusable unusable +++ +++ +++ +++ +++ ++ extra extra 4.00 unusable unusable unusable +++ +++ +++ +++ +++ extra extra 5.00 unusable unusable unusable unusable +++ +++ +++ +++ extra extra 6.00 unusable unusable unusable unusable unusable unusable unusable unusable +++ ++

(15) The above-shown table evidences that the appearance of metal ceramic substrates on which the metal (copper) was ablated is improved from right to left (which means from a high laser power to a low laser power and from a low laser speed to a high laser speed),

(16) On the other hand, an economic reasonable processing results in the above-shown table from left to right (which means with a lower number of laser passages over the metal ceramic substrate).

(17) The values indicated bold are preferred.

(18) Based on data provided in the above-shown table, a mathematical relationship between laser power (W) and laser speed (m/sec, effective) can be derived.

(19) The diagram in FIG. 1 shows the same relationship between laser power (W) and laser speed (m/sec): In this diagram of FIG. 1 the unusable combinations of laser power and laser speed and the preferred range (+ to +++ and extra) are presented as a logarithmic function, which is defined as follows:
y≤4.7 ln x−15  General acceptable range:
y≤5.0 ln x−18,  Preferred range:
with
x=laser power in W; and
y=laser speed (effective).

(20) This means: With a laser power of 100 W a laser speed according to the present invention is less than 6.6 m/sec (general acceptable range) and 5.0 m/sec (preferred range).

(21) Taking this relationship between laser power and laser speed (effective) Into consideration, further examples are carried out and result into the following findings:

(22) TABLE-US-00016 Laser processing speed [m/sec] Preferred range for Laser Process the process power limitation (maximum speed) 30 1.0 40 2.3 0.4 50 3.4 1.6 60 4.2 2.5 70 5.0 3.2 80 5.6 3.9 90 6.1 4.5 100 6.6 5.0 110 7.1 5.5 120 7.5 5.9 130 7.9 5.3 140 8.2 6.7 150 8.5 7.1

(23) Based on the above findings the following statements can be derived:

(24) (1) Laser Power

(25) Preferred are laser powers of 30 W or more.

(26) Further preferred are laser powers of 60 W or more (for economic reasons).

(27) More preferred are laser powers of 80 W or more.

(28) (2) Laser Speed

(29) Preferred are laser speeds (effective) of 0.2 m/sec or more.

(30) Further preferred are laser speeds of 0.5 m/sec or more.

(31) More preferred are laser speeds of 0.75 m/sec or more.

(32) The above-presented results are based on the following examples:

First Example—According to the Present Invention

(33) a. Parameters as mentioned above b. Laser power 70 Watt c. Laser speed (effective): 1.0 m/sec d. Ceramic thickness 0.63 mm; copper thickness 0.30 mm e. Results: i. Good optical appearance ii. Only few melting phases; only few copper oxidation iii. A low optical roughness of the surface iv. Processing speed acceptable

Second Example—According to the Invention

(34) a. Parameters as mentioned above b. Laser power 100 Watt c. Laser speed (effective): 1.5 m/sec d. Ceramic thickness 0.38 mm; copper thickness 0.30 mm e. Results: i. Acceptable optical appearance ii. More melting phases and copper oxidation iii. Higher optical roughness of the surface iv. Processing speed low

Third Example—According to the Invention

(35) a. Parameters as mentioned above b. Laser power: 50 Watt c. Laser speed (effective): 3.0 m/sec d. Ceramic thickness 0.63 mm; copper thickness 0.25 mm e. Results: i. A very good optical appearance ii. Almost no melting phases and copper oxidation iii. Almost no optical roughness of the surface iv. Processing speed very low; for economical reason this procedure is less suitable.

Forth Example—not According to the Invention

(36) a. Parameters as mentioned above b. Laser power: 60 Watt c. Laser speed (effective): 6 m/sec d. Ceramic thickness 0.38 mm; copper thickness 0.20 mm e. Results: i. The copper is ablated very slowly ii. The processing speed is too low iii. Almost no residues iv. Very low optical roughness of the surface v. Processing speed so low that for economical reason the process cannot be applied

Fifth Example—According to the Invention

(37) a. Parameters as mentioned above b. Laser power 90 Watt c. Laser speed (effective): 0.25 m/sec d. Ceramic thickness 0.63 mm; copper thickness 0.30 mm e. Results: i. Many melt phases remain on the surface ii. Copper is oxidized in a high degree iii. Almost no residues iv. A very high optical roughness of the surface v. For application with low requirements of the quality a parameter area is given with high economic efficiency

Sixth Example—not According to the Invention

(38) a. Parameters as mentioned above b. Laser power: 100 Watt c. Laser speed (effective): 0.15 m/sec d. Ceramic thickness 0.63 mm; copper thickness 0.40 mm e. Result: i. The Quality of the copper ablation is very bad; no use of these process parameters is expected ii. The material becomes very warm during processing iii. Process parameters are technically not feasible