US 11,792,940 B2
Metal sublayer sensing in multi-layer workpiece hole drilling
Guy Soffer, Kiryat Ono (IL)
Assigned to DRILLIANT LTD., Kiryat Ono (IL)
Filed by Drilliant Ltd., Kiryat Ono (IL)
Filed on Feb. 1, 2021, as Appl. No. 17/164,340.
Application 17/164,340 is a continuation of application No. 16/022,052, filed on Jun. 28, 2018, granted, now 10,932,370.
Prior Publication US 2021/0161017 A1, May 27, 2021
This patent is subject to a terminal disclaimer.
Int. Cl. H05K 3/00 (2006.01); H05K 1/02 (2006.01); B23K 26/06 (2014.01); B23K 26/064 (2014.01); B23K 26/03 (2006.01)
CPC H05K 3/0038 (2013.01) [B23K 26/032 (2013.01); B23K 26/0604 (2013.01); B23K 26/064 (2015.10); H05K 1/0269 (2013.01); H05K 2203/0207 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A method of monitoring laser drilling of a workpiece, the method comprising:
a) transmitting, by a source of electromagnetic radiation, a measurement pulse in open air to the workpiece,
wherein the pulse has at least one wavelength with higher energy than a work-function of a metal layer in the workpiece,
and gives rise to electrically charged molecules deriving from interactions of air molecules with free electrons emitted by the metal layer in the workpiece, a quantity of the free electrons emitted being dependent on an extent of exposure of the metal of the workpiece;
b) receiving, by an anode, at least part of the electrically charged molecules;
c) accumulating, by a resettable electric charge sensor (ECS) operably connected to the anode, electric charge derivative of charged molecules received at the anode;
d) receiving, by a control unit, from the ECS, at least one value indicative of a quantity of at least part of charged molecules received at the anode since ECS activation;
e) determining, by the control unit, from the at least one value, a second value indicative of a quantity of charged molecules received at the anode since ECS activation that were derivative of electrons emitted responsive to the measurement pulse; and
f) performing at least one of a group consisting of:
i. identifying at least one of: exposure or disappearance of the metal layer in accordance with, at least, the second value, and
ii. controlling drilling in accordance with, at least, the second value.