Techniques for print ink droplet measurement and control to deposit fluids within precise tolerances

A method of fabricating permanent layers on respective substrates, each permanent layer and respective substrate to form part of a respective electronic device, the method comprising:

• using a print head to print a liquid onto each one of the respective substrates, the liquid providing material to form the permanent layer on the one the respective substrates, the print head having nozzles that each eject droplets of the liquid;
• transporting each of the respective substrates in succession to-and-from a location in which each of the respective substrates can be printed on using the print head;
• transporting the print head between a first position, in which the print head can print the respective droplets of liquid onto the respective substrates, when at the location, and a second position;
• and
• selectively moving a system comprising a light source, a light detector, and a light path extending from the light source to the light detector in at least two independent dimensions relative to the print head, the light source, the light detector and the light path being mounted in fixed positional relationship relative to one another, to generate an electronic output representing measurement of a characteristic of a droplet of the liquid ejected from a selected one of the nozzles during droplet flight;
• wherein at least one of using the print head, transporting each of the respective substrates, and transporting the printhead is performed in dependence on the measurement of the characteristic.

A method of fabricating permanent layers on respective substrates, each permanent layer and respective substrate to form part of a respective electronic device, the method comprising:

• using a print head to print a liquid onto each one of the respective substrates, the liquid providing material to form the permanent layer on the one the respective substrates, the print head having nozzles that each eject droplets of the liquid;
• transporting each of the respective substrates in succession to-and-from a location in which each of the respective substrates can be printed on using the print head;
• transporting the print head between a first position, in which the print head can print the respective droplets of liquid onto the respective substrates, when at the location, and a second position;
• and
• selectively moving a system comprising a light source, a light detector, and a light path extending from the light source to the light detector in at least two independent dimensions relative to the print head, the light source, the light detector and the light path being mounted in fixed positional relationship relative to one another, to generate an electronic output representing measurement of a characteristic of a droplet of the liquid ejected from a selected one of the nozzles during droplet flight;
• wherein transporting the print head and selectively moving are performed during a time when none of the respective substrates are at the location, and wherein the method further comprises automatically measuring the characteristic for a droplet from at least one of the nozzles in between printing of the liquid onto successive ones of the respective substrates, as a function of position of at least one of the successive ones.