A phototool is a printed film used in the process of manufacturing a
printed circuit board
A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in Electrical engineering, electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a L ...
(PCB). The phototool is used as a mask to expose a
photoresist material. The main alternative to using phototools is
maskless lithography, more commonly referred to as direct imaging.
Traditionally, phototools were made with
silver halide film
Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...
or
diazo film
Whiteprint describes a document reproduction produced by using the diazo chemical process. It is also known as the blue-line process since the result is blue lines on a white background. It is a contact printing process which accurately reproduce ...
, but in recent years, many suppliers have come out with films that do not fit into either of these categories. All dry-film phototools are printed using a similar process to film photograph.
The steps for using a phototool are as follows:
* A PCB (typically consisting of a laminate material with copper adhered to the surface) is prepared and cleaned.
* The PCB is coated with a
photoresist material that can be cured with UV light
* The phototool is positioned over the PCB
* UV light (or other
actinic radiation
Actinism () is the property of solar radiation that leads to the production of photochemical and photobiological effects. ''Actinism'' is derived from the Ancient Greek ἀκτίς, ἀκτῖνος ("ray, beam"). The word ''actinism'' is found, ...
) shines through the phototool, selectively curing the material.
* The uncured material is washed away, usually using a mild water-based alkali solution.
* PCB can continue to a
photolithography
In integrated circuit manufacturing, photolithography or optical lithography is a general term used for techniques that use light to produce minutely patterned thin films of suitable materials over a substrate, such as a silicon wafer, to protect ...
step such as surface plating, or a
photoengraving step such as etching away unwanted material.
References and further reading
Chemistry of PhotographyBy: Dr. Drew Myers, Chemistry Coordinator
* Mees, C.E.K, and James, T.H., The Theory of the Photographic Process, 3rd ed., The Macmillan Co., New York, 1966.
Electronics manufacturing