Systems and methods for removing undesired metal within vias from printed circuit boards
A method is provided for modifying a via from a PCB including a plurality of subassemblies comprising a plurality of layers. The method may include drilling a via of the PCB to form a through-hole to remove an unwanted material in the via of the PCB. The method may also include depositing a carbon-based material over an inner wall of the through-hole. The method may further include back drilling a first portion of the through-hole by a drill from the top of the PCB to form a first blind via. The method may also include selectively plating a conductive material over the carbon-based material to form a plated through-hole.
1. A method of modifying a via of a PCB to form a stub-less through-hole, the method comprising:
drilling a via of the PCB comprising an unwanted material to form a through-hole by removing the unwanted material in the via of the PCB;
depositing a seed material directly over an inner wall of the through-hole, wherein the seed material is a seed for plating a conductive material;
back drilling a first portion of the through-hole by using a drill from the top of the PCB to form a first blind via, wherein the drill drills through the seed material and automatically stops drilling at an internal conductive trace of the PCB; and
selectively plating the conductive material over the seed material to form a stub-less plated through-hole,
wherein the drill comprises:
an inner core comprising a conductive material;
an outer coating layer comprising a non-conductive material disposed over the inner core, the outer coating having a first and a second vertical portions and a horizontal portion under a bottom of the inner core, the first vertical portion having a first tip end and the second vertical portion having a second tip end opposite to the first tip end near the bottom of the inner core; and
a coating disposed over the outer coating layer near the bottom of the inner core between the first and second tip ends.
2. The method of claim 1 , wherein the drill has a diameter larger than the via of the PCB, wherein the non-conductive material of the outer coating layer comprises diamonds.
3. The method of claim 1 , wherein the first blind via is larger than the through-hole having a first diameter.
4. The method of claim 1 , wherein the plated conductive material does not adhere to the first blind via.
5. The method of claim 1 , wherein the first blind via is aligned with the through-hole.
6. The method of claim 1 , further comprising back drilling a second portion of the PCB below the through-hole from the bottom of the PCB to form a second blind via.
7. The method of claim 6 , wherein the second blind via is larger than the through-hole.
8. The method of claim 6 , wherein the plated conductive material does not adhere to the second blind via.
9. The method of claim 1 , wherein the plated conductive material comprises copper.
10. The method of claim 1 , wherein the PCB comprises a plurality of subassemblies comprising a plurality of layers.
11. The method of claim 1 , wherein the seed material comprises electroless copper.
12. The method of claim 1 , wherein the seed material is conductive.