Opto-coupler with high reverse breakdown voltage and high isolation potential
An opto-coupler and a process for fabricating an opto-coupler are disclosed. The opto-coupler includes at least one light-emitting diode and a photodiode for galvanically isolating electric circuits. The optical components are mounted in a yielding material, such as silicone rubber, in a housing. The interior walls are coated with a pigmented yielding coating which includes TiO 2 to enhance light reflection inside the housing and increase the current transfer efficiency of the device. The opto-coupler has a high dielectric breakdown voltage and is immune to radiation. The device can be employed in space applications.
1 . An opto-coupler comprising:
a housing having a side wall, a bottom and a top,
at least one light-emitting diode (LED) and a photodetector (PD) disposed in the housing, said PD receiving light from the at least one LED,
a coating applied to an inside of the wall and bottom of the housing, said coating comprising a yielding material and a pigment dispersed in the yielding material and designed to enhance reflection of the light emitted by the at least one LED, said coating having a thickness so as not to contact the at least one LED and the PD,
a yielding, optically transparent filler material filling a remaining space between the coated walls and bottom of the housing and enclosing the at least one LED and the PD, and
a cover layer made of the yielding coating, so that the coating and the cover layer completely enclose the at least one LED and the PD.
2 . The opto-coupler of claim 1 , wherein the yielding material of the coating and the yielding filler material are identical.
3 . The opto-coupler of claim 1 , wherein the yielding material of the coating comprises a silicone-rubber-based material.
4 . The opto-coupler of claim 1 , wherein the yielding filler material comprises a silicone-rubber-based material.
5 . The opto-coupler of claim 1 , wherein the pigment comprises titanium dioxide (TiO 2 ).
6 . The opto-coupler of claim 1 , wherein a spacing between the at least one LED and the PD is in a range from approximately 0.1 mm to approximately 5 mm.
7 . The opto-coupler of claim 6 , wherein the spacing between the at least one LED and the PD is between approximately 0.2 mm and approximately 0.5 mm.
8 . The opto-coupler of claim 1 , wherein the coating has a composition of approximately 20 parts by weight of pigment to 80 parts by weight of the yielding material.
9 . A process of manufacturing an opto-coupler, comprising the steps of:
mounting at least one light-emitting diode (LED) and a photodetector (PD) in a housing,
coating interior surfaces of the housing with a light-reflecting first yielding compound,
filling a space between the coated interior surfaces of the housing with a second yielding compound, thereby encapsulating the at least one LED and the PD, and covering a top opening of the housing with the first yielding compound.
10 . The process of claim 9 , wherein coating the interior surfaces comprises sequentially applying several layers of the first yielding compound and curing the applied layers before application of a subsequent layer.
11 . The process of claim 9 , further comprising the step of priming the interior surfaces before coating.
12 . The process of claim 9 , wherein the pigment comprises titanium dioxide (TiO 2 ).
13 . The process of claim 9 , wherein the first and second yielding compounds comprise silicone rubber.
14 . The process of claim 9 , wherein coating includes applying the light-reflecting first yielding compound with a thickness so as not to contact optically transmissive surfaces of the at least one LED and the PD.