Method for contactless testing of integrated circuit packaging boards under atmospheric conditions

Claim 2

Method of testing the integrity of conducting paths on or in a non-conducting circuit substrate under atmospheric conditions, the surface of said substrate and pads on said surface which are connected to said conducting paths, being covered by a layer of electron-sensitive material (15) and layers (15, 17) which allow electron tunneling from pads, the method comprising following steps: - (a) generating charges in at least one selected pad by stimulating photon-assisted tunneling of electrons from each selected pad by a focused laser beam, thus inducing a specific voltage level in each selected pad (P21), and also in each non-selected pad (P22) which is electrically connected to a selected pad; - (b) flooding the whole area of the substrate surface with a laser beam to excite voltage-dependent photon-assisted electron tunneling from pads, the intensity of said electron tunneling being dependent on the potential of each respective pad; and - (c) detecting an excitation pattern in said electron-sensitive layer (15) which is caused by said electron tunneling stimulated in step (b), to distinguish pads being electrically connected to said selected pads which were charged in step (a), from other pads.

Claim 3

Method of testing the integrity of conducting via connections in a circuit substrate consisting of non-conducting material under atmospheric conditions, each of said via connections having one pad (P31) on one surface (11A) and another pad (P32) on the other surface (11B) of the substrate, both surfaces (11A, 11B) of said substrate being covered by layers (13, 17, 13ʹ 17ʹ) which allow electron tunneling from pads, and said other surface (11B) being also covered by a layer of electron-sensitive material (15ʹ), the method comprising following steps: - (a) generating charges in at least one selected pad on said one surface (11A) of the substrate by a focused laser beam whose energy is sufficient to cause photon-assisted tunneling of electrons from each selected pad but insufficient to cause pho toelectron emission from said non-conducting substrate material, thus inducing a specific voltage level in each selected pad (P41, P61) on said one surface, and also in each pad (P42, P62) on said other surface which is electrically connected to a selected pad on said one surface; - (b) flooding the whole area of said other surface (11B) with a laser beam to excite voltage-dependent photon-assisted electron tunneling from pads, the intensity of said electron tunneling being dependent on the potential of each respective pad; and - (c) detecting an excitation pattern in said electron-sensitive layer (15ʹ) which is caused by said electron tunneling stimulated in step (b), to distinguish pads on said other surface being electrically connected to selected pads on said one surface, from pads on said other surface which are not electrically connected to a selected pad on said one surface.

Claim 4

Method of testing the integrity of conducting via connections in a circuit substrate consisting of non-conducting material under atmospheric conditions, each of said via connections having one pad (P31) on one surface (11A) and another pad (P32) on the other surface (11B) of the substrate, both surfaces (11A, 11B) of said substrate being covered by layers (13, 17, 13ʹ 17ʹ) which allow electron tunneling from pads, and said other surface (11B) being also covered by a layer of electron-sensitive material (15ʹ), the method comprising following steps: - (a) generating charges in at least one selected pad on said one surface (11A) of the substrate by a focused laser beam whose energy is sufficient to cause photon-assisted tunneling of electrons from each selected pad but insufficient to cause pho toelectron emission from said non-conducting substrate material, thus inducing a specific voltage level in each selected pad (P41, P61) on said one surface, and also in each pad (P42, P62) on said other surface which is electrically connected to a selected pad on said one surface; - (b) flooding the whole area of said other surface (11B) with a laser beam to excite voltage-dependent photon-assisted electron tunneling from pads, the intensity of said electron tunneling being dependent on the potential of each respective pad; and - (c) detecting an excitation pattern in said electron-sensitive layer (15ʹ) which is caused by said electron tunneling stimulated in step (b), to distinguish pads on said other surface being electrically connected to selected pads on said one surface, from pads on said other surface which are not electrically connected to a selected pad on said one surface.

Claim 5

Method in accordance with claim 2, characterized in that - the substrate (11) is turned over by 180 degree between step (a) and step (b), so that a laser device (19) for generating a focused laser beam and a flooding laser beam, and detection apparatus for detecting the excitation pattern can be located all on one side of the substrate location.

Claim 6

Method in accordance with claim 3, characterized in that - the substrate (11) is not moved during the whole testing operation; that the step of directing a focused laser beam to selected pads is executed on one side of the substrate's location; and that the steps of flooding the other surface by a laser beam and of detecting the excitation pattern are executed on the other side of the substrate's location.

Claim 7

Method in accordance with claim 1, characterized in that prior to the execution of step (a), the following step is executed: - deposition of a layer of insulating material (13) over the substrate's surface and all pads located on it; deposition of a layer of electroluminiscent material (15) over said insulating layer; and deposition of a thin transparent layer of conducting material (17) on top of said electroluminiscent layer (15).

Claim 8

Method in accordance with claim 2, characterized in that prior to the execution of step (a), the following step is executed: - deposition of a layer of insulating material (13, 13ʹ) over both of the substrate's surfaces and all pads located on them; deposition of a layer of electroluminiscent material (15ʹ) over said insulating layer on at least one of said surfaces; and deposition of a final thin transparent layer of conducting material (17, 17ʹ) over both surfaces.

Claim 9

Method of testing the integrity of conducting via connections in a circuit substrate consisting of non-conducting material, each of said via connections having one pad (P31) on one surface (11A) and another pad (P32) on the other surface (11B) of the substrate, said one surface (11A) of said substrate being covered at least by an insulating layer (13) and a thin conducting layer (17), and said other surface (11B) being covered at least by a layer of electron-sensitive material (15ʹ) and a thin layer of conducting material (17ʹ), characterized by the following steps: - (a) generating charges in all pads (P31, P41, P51, P61) on said one surface (11A) of the substrate by a flooding laser beam whose energy is sufficient to cause photon-assisted tunneling of electrons from said pads but insufficient to cause photoelectron emission from said non-conducting substrate material, thus inducing a specific voltage level in each pad on said one surface, and also in each pad (P32, P42, P52, P62) on said other surface (11B) which is electrically connected to a pad on said one surface; - (b) flooding the whole area of said other surface (11B) with a laser beam to stimulate voltage-dependent photon-assisted electron tunneling from pads, the intens ity of said electron tunneling being dependent on the potential of each respective pad; and - (c) detecting the excitation pattern in said electron-sensitive layer (15ʹ) caused by said electron tunneling stimulated in step (b), to distinguish pads on said other surface being electrically connected to pads on said one surface, from pads on said other surface which are not electrically connected to a pad on said one surface.

Claim 10

Method of testing the integrity of conducting via connections in a circuit substrate consisting of non-conducting material, each of said via connections having one pad (P31) on one surface (11A) and another pad (P32) on the other surface (11B) of the substrate, said one surface (11A) of said substrate being covered at least by an insulating layer (13) and a thin conducting layer (17), and said other surface (11B) being covered at least by a layer of electron-sensitive material (15ʹ) and a thin layer of conducting material (17ʹ), characterized by the following steps: - (a) generating charges in all pads (P31, P41, P51, P61) on said one surface (11A) of the substrate by a flooding laser beam whose energy is sufficient to cause photon-assisted tunneling of electrons from said pads but insufficient to cause photoelectron emission from said non-conducting substrate material, thus inducing a specific voltage level in each pad on said one surface, and also in each pad (P32, P42, P52, P62) on said other surface (11B) which is electrically connected to a pad on said one surface; - (b) flooding the whole area of said other surface (11B) with a laser beam to stimulate voltage-dependent photon-assisted electron tunneling from pads, the intens ity of said electron tunneling being dependent on the potential of each respective pad; and - (c) detecting the excitation pattern in said electron-sensitive layer (15ʹ) caused by said electron tunneling stimulated in step (b), to distinguish pads on said other surface being electrically connected to pads on said one surface, from pads on said other surface which are not electrically connected to a pad on said one surface.

Claim 11

Method of testing the integrity of conducting paths on or in a non-conducting circuit substrate under atmospheric conditions, the surface of said substrate and pads on said surface which are connected to said conducting paths, being covered by a layer of electrooptic material and a thin layer of conducting material, characterized by the following steps: - (a) generating charges in at least one selected pad by stimulating photon-assisted tunneling of electrons from each selected pad by a focused laser beam, thus inducing a specific voltage level in each selected pad and in each non-selected pad which is electrically connected to a selected pad, - (b) flooding the whole area of the substrate's surface with a light wave from a polarized light source to thus generate a reflected light wave whose polarization pattern reflects a location-dependent polarization rotation in the electrooptic layer, which rotation in turn is dependent on the voltage between any pad at the respective location and the thin conducting layer; and - (c) detecting said light wave polarization pattern to distinguish pads being electrically connected to pads previously selected in step (a), from other pads.

Claim 12

Method of testing the integrity of conducting paths on or in a non-conducting circuit substrate under atmospheric conditions, the surface of said substrate and pads on said surface which are connected to said conducting paths, being covered by a layer of electrooptic material and a thin layer of conducting material, characterized by the following steps: - (a) generating charges in at least one selected pad by stimulating photon-assisted tunneling of electrons from each selected pad by a focused laser beam, thus inducing a specific voltage level in each selected pad and in each non-selected pad which is electrically connected to a selected pad, - (b) flooding the whole area of the substrate's surface with a light wave from a polarized light source to thus generate a reflected light wave whose polarization pattern reflects a location-dependent polarization rotation in the electrooptic layer, which rotation in turn is dependent on the voltage between any pad at the respective location and the thin conducting layer; and - (c) detecting said light wave polarization pattern to distinguish pads being electrically connected to pads previously selected in step (a), from other pads.