Non-destructive laser optical integrated circuit package marking
View Patent ↗A method is provided for laser optically marking integrated circuit (IC) packages in a non-destructive manner. The method provides an IC die encapsulated as a package in a compound of glass spheres and epoxy. An acute angle is defined between a laser optical path and an IC package planar surface. The IC package surface is scanned with a laser, and in response to ablating the IC package surface, a legible mark on the planar surface.
1. A method for laser optically marking integrated circuit (IC) packages in a non-destructive manner, the method comprising:
providing an IC die encapsulated as a package in a compound of glass spheres and epoxy;
defining an acute angle, exclusively in the range of ±(0 to 70) degrees, between a laser optical path and an IC package planar surface;
scanning the IC package surface with a laser; and,
in response to ablating the IC package surface, forming a legible mark on the IC package surface.
2. The method of claim 1 wherein scanning the IC package surface with the laser includes scanning with a laser having a wavelength that is minimally absorbed by the glass spheres in the epoxy compound of the IC package.
3. The method of claim 1 wherein scanning the IC package surface with the laser includes scanning with carbon dioxide laser having a wavelength of about 10.6 microns.
4. The method of claim 1 wherein providing the IC die encapsulated with the compound of glass spheres and epoxy includes providing an IC die encapsulating with an epoxy/glass sphere layer having a thickness of less than 300 microns.
5. The method of claim 1 wherein providing the IC die encapsulated with the compound of glass spheres and epoxy includes providing an IC die encapsulating with an epoxy/glass sphere layer having glass spheres with a diameter of greater than 10 microns.
6. The method of claim 1 wherein providing the IC die encapsulated with the compound of glass spheres and epoxy includes providing an IC die encapsulated with a first thickness of compound; and,
wherein scanning the IC package surface with a laser includes scanning the laser through optical pathways, formed from consecutively aligned glass spheres in the compound, having a path length greater than the first thickness.
7. The method of claim 1 wherein providing the IC die encapsulated with the compound of glass spheres and epoxy includes providing an IC package with a first plurality of optical paths having a first path length equal to the first thickness, and a second plurality of optical paths, less than the first plurality, having a second path length greater than the first path length.
8. The method of claim 1 wherein defining the acute angle includes defining an angle in the range of ±(60 to 70) degrees from the IC package planar surface.
9. The method of claim 1 wherein forming the legible mark in response to ablating the IC surface includes ablating the IC package surface to a depth of about 25 microns, or greater.
10. The method of claim 1 wherein scanning the IC package surface with the laser includes scanning with a laser having a wavelength that is substantially absorbed by the epoxy in the epoxy compound of the IC package.
11. The method of claim 1 wherein scanning the IC package surface with a laser includes scanning the laser without encountering any optical pathways, formed from consecutively aligned glass spheres in the compound.
12. A method for laser optically marking integrated circuit (IC) packages in a non-destructive manner, the method comprising:
providing an IC die encapsulated as a package in a compound of glass spheres and epoxy;
defining only a first acute angle between a laser optical path and an IC package planar surface;
scanning the IC package surface with a laser; and,
forming an ablation mark on the IC package surface having an ablation angle equal to the first acute angle.