Method for forming multi-layer bumps on a substrate
View Patent ↗A method for forming multi-layer bumps on a substrate includes depositing a first metal powder on the substrate, and selectively melting or reflowing a portion of the first metal powder to form first bumps. A second metal powder is then deposited on the first bumps, and melted to form second bumps on the first bumps. A masking plate is disposed over the substrate to select the portions of the metal powders that are melted and the metal powders are melted via an irradiation beam. The multi-layer bump is formed without the need for any wet chemicals.
1. A method for forming a binal-layer bump on a substrate, comprising:
depositing a first metal powder on the substrate;
placing a first masking plate over the substrate, the first masking plate having at least one aperture;
melting the first metal powder to form a first bump;
depositing a second metal powder over at least the first bump; placing a second masking plate over the substrate, the second masking plate having at least one aperture; and
melting the second metal powder to form a second bump on the first bump, wherein the first bump and the second bump form the binal-layer bump and wherein the binal-layer bump is surrounded by remaining portions of the first and second metal powders.
2. The method for forming a binal-layer bump according to claim 1 , wherein melting the first metal powder further comprises:
melting a selected portion of the first metal powder by irradiating the selected portion through the at least one aperture.
3. The method for forming a binal-layer bump according to claim 2 , wherein melting the second metal powder further comprises:
melting a selected portion of the second metal powder by irradiating the selected portion through the aperture of the second masking plate.
4. The method for forming a binal-layer bump according to claim 1 , wherein a melting point of the second metal powder is lower than a melting point of the first metal powder.
5. The method for forming a binal-layer bump according to claim 1 , wherein the first metal powder and the second metal powder each have a particle size between about 5 microns to about 10 microns.
6. The method for forming a binal-layer bump according to claim 5 , wherein the first metal powder comprises one of copper and high lead solder and the second metal powder comprises a eutectic solder.
7. The method for forming a binal-layer bump according to claim 1 , further comprising cleaning a bond pad on the substrate before depositing the first metal powder.
8. The method for forming a binal-layer bump according to claim 7 , wherein the cleaning step comprises irradiating the bond pad to burn out any contaminants thereon.
9. The method for forming a binal-layer bump according to claim 1 , wherein melting the first metal powder further comprises irradiating a portion of the first metal powder with a programmable single laser beam.
10. The method for forming a binal-layer bump according to claim 1 , further comprising removing any unmelted portions of the first and second metal powders remaining on the substrate.
11. A method for forming a multi-layer connector on a substrate, comprising:
depositing a first metal powder on the substrate;
placing a first masking plate over the substrate, the first masking plate having at least one aperture;
irradiating a selected portion of the first metal powder to form a first bump;
depositing a second metal powder over the first bump; placing a second masking plate over the substrate, the second masking plate having at least one aperture; and
irradiating the second metal powder to form a second bump on the first bump, wherein the first bump and the second bump form the multi-layer connector and wherein the binal-layer bump is surrounded by remaining portions of the first and second metal powders.
12. The method forming a multi-layer connector according to claim 11 , wherein a melting point of the second metal powder is lower than a melting point of the first metal powder.
13. The method forming a multi-layer connector according to claim 11 , wherein the first metal powder and the second metal powder each have a particle size between about 5 microns to about 10 microns.