Method of making interlayer panels
Innerlayer panels are provided with high density fiducials during manufacture. The fiducials can be identified using X-rays without etching away portions of the innerlayer panel to expose the fiducials.
1. A method of making an innerlaver panel, comprising:
providing a metallic foil;
forming at least one fiducial over the foil;
forming at least one feature over the foil;
applying a dielectric over the at least one feature and over the at least one fiducial, thereby embedding the at least one fiducial and the at least one feature; and identifying the location of the at least one fiducial using X-rays, further comprising:
applying a second foil to the dielectric before identifying the location of the at least one fiducial;
forming at least one register hole in the innerlayer panel according to the identified location of the at least one fiducial;
positioning a photo-tool according to the location of the at least one register hole;
imaging the foils with the photo-tool; and
etching the foils, wherein etching results in terminations for the embedded at least one feature.
2. The method of claim 1 , wherein providing a metallic foil comprises:
providing a foil comprising copper.
3. The method of claim 1 , wherein forming at least one fiducial comprises: forming at least one fiducial comprising tungsten.
4. The method of claim 3 , wherein the at least one fiducial is formed from a paste containing:
glass; and
tungsten in excess of 53% by weight.
5. The method of claim 3 , wherein:
a dried print thickness of the at least one fiducial is at least 15 microns.
6. The method of claim 1 , wherein:
forming at least one feature and forming at least one fiducial comprise at least one firing step.
7. The method of claim 1 , wherein:
forming at least one feature and forming at least one fiducial comprise curing of a thick-film polymer paste.
8. The method of claim 1 , wherein:
the at least one feature comprises at least one capacitor or resistor.
9. The method of claim 1 , further comprising:
applying an encapsulant over the at least one fiducial prior to applying the dielectric.
10. The method of claim 9 , wherein: the dielectric is a prepreg.