In order to determine the correct development time, you will need to determine the “Break Point” This is the point where the developer is removed just down to the metal. This time will obviously vary depending on the type of film and developer film used. Once this time has being determined, the panels should then be left in the developer solution for approximately 40% of this time.
Yes the Roller Tinning machine rollers can be easily adjusted by following the written procedure to adjust the gap between the rollers which the thumb wheel adjusting screws.
Yes the PCB roller tinning machine will be more than suitable for this application. The machine takes approximately 10 -12 seconds to Flux and Roller Tin each circuit board.
- Artwork is normally created with a CAD programme and the artwork created with a Photoplotter like the Fortex FP25000.
- The correct type of metal is selected and cleaned. The metal is then laminated on both sides using Dry Film Photo resist normally using a Dry Film Hot Roll Laminator.
- The artworks previously created is then placed over both sides of the metal plate and exposed in a UV Exposure unit.
- The areas of the Photoresist that has being protected from the UV light by the artwork remains soft and is chemically developed away, leaving the metal exposed ready for etching. The component image remains protected by the resist.
- The prepared metal sheets are now passed through the spray Etching Machine.
- The Final stage of the Photochemical milling is to strip off the resist the etched component and ensure the metal is clean.
It is strongly recommended that for all adding or removing of Film to and from the Photoplotter as well as developing and fixing that dark room conditions are required with a green safe light illumination.
Yes both the Fortex 305 and 605 Dry Film Hot Roll Laminators offer this facility as standard.
Yes all dry film laminator should be performed ideally with special Safe Yellow. Low wattage incandescent lamps or UV proofed fluorescent lights can be used if a Yellow safe light is not available.
Laminated board/plates must be stored in a Light Tight enclosure if they are not to be processed immediately. They can generally be stored for up to 7 days before being exposed.
Depending on the type of UV unit being used this is normally 2 to 2 ½ Minutes. Always remember to allow the UV tubes to warm up first for 4-5 minutes.
This comes down to a number of factors but assuming standard single sided Fortex FR4 Photoboard is used 10 litres of Ferric Chloride solution will etch approximately 14 Panels 18” x 12”.
-Emulsion on the artwork could be on the wrong side
-The art work could have being over exposed,
-There may be poor contact between the artwork and material, check the vacuum on the UV exposure unit or that the pressure applied by Foam inserts on the UV exposure unit is adequate.
-The details of the artwork may be beyond the specification of the printer being used to generate the photo tool, a Photoplotter may be required.
It is essential that the Printed circuit board to be roller tinned has had the required pre cleaning and fluxing operations. The top roller pressure needs to be correctly adjusted to give the correct level of thermal conductivity between the bottom roller and the copper and that the roller speed is set correctly. Poor roller tinning can also be caused by two much Flux on the PCB or the Tinning Salts need changing.
This can be caused by poor quality artwork, handling damage to the Photo resist (Avoid handling the board and putting it down on rough surfaces) or dirt on the artwork or print frame.
When Etching silver, Ferric Nitrate FeN3O9 Etchant should be used, normally with the Fortex range of Spray etching machines a working temperature of 50 degrees Celsius is the optimum set point.
There are obviously many factors that affect the rate of Etching, such as Temperature of the Etchant, Freshness of Etchant, the ratio of copper being Etched away against the total panel size etc but as a rough figure it should take one minute to Etch 1oz (35um) copper with fresh warm Ferric Chloride FeCl3
Standard 40um Fortex Photopolymer Dry Film Photo resist can be used when etching silver.
Fortex supply a range of automated PCB brushing machines which can be used for this exact requirement with a range of different brushes to suit.
This can be caused by a few factors. The rollers of the Roller Tinning machine have not being adjusted correctly such that they are parallel, or the solder temperature is to high or the top roller pressure is to high.
The Fortex standard Hot Roll Dry Film Laminator operates up to 130 degrees, but there is an optional version with a maximum operating temperature of 160 degrees Celcius with each Hot Roller having the facilty to have the temperature independently set.
There are many advantages some of the key ones are:-
-The only “Tooling” to wear out is the Artwork which can easily and cheaply be reproduced using a Photoplotter.
-Chemical Milling through an Etching machine produces burr free components, eliminating the need for time consuming deburring.
-The internal structure of the metal is unaltered such as hardness, grain structure and ductility
-Prototyping costs can be much cheaper as more than one design can be etched on one sheet
-Artworks can be rapidly changed meaning at the design phase it is cheap to change prototype designs.
-The engineering concept prototype to full production runs of many millions of parts can be rapidly instigated as the same artwork is used.
When cutting these types of Laminate materials with a Bandsaw or circular saw the blades will become dull or blunt very quickly and there is the risk of the inhalation of very harmful dusts produced from the cutting operation. The dust can also cause skin irritation. If using a manual saw it can also be very easy to accidentally scratch the Photoresist coating. Cutting with any form of saw also has the potential to raise a burr which when exposing the board on the artwork can allow the UV light to leak between the board and artwork. Using a PCB Shear cutter gives a clean edge to the work piece.
PTH refers to Plated Through Holes on Printed Circuit Boards. This technology allows for circuit board components to make contact with the required conductive layers on Multilayer boards. With Surface mount technology (SMT) boards this Plated through holes are often referred to as Vias. Through hole plating is normally a chemical process.
Mechanical Etching involves the use of a precisely controlled multi-axis machine tool with a suitable milling cutter to remove the unwanted copper material, Chemical Milling involves the use of a family of corrosive liquids to dissolve away unwanted copper to give the required pattern
“Chemical Etching” and “Photo Etching” are both the same process but are both terms that are often interchangeably used. “Chemical Milling” is another term often used for the same process.
During the procedure of developing the dry film after UV exposure, with Positive working Dry Film Photo resist the areas of the Dry Film that have being exposed to UV light will be removed, and areas of Dry Film that have not being exposed to UV light will remain. (So for example when producing circuit boards a positive artwork should be used (Black on Artwork = Copper))
With Negative working Dry film Photo resist (Like the Fortex range of Dry Films) after UV exposure and developing, areas of the Dry film that have being exposed to UV light will remain, and the areas of Dry Film that have not being exposed to UV light be removed. (So for example when producing circuit boards a negative artwork should be used (Black on Artwork = No Copper))
Any thickness of sheet metal material can be surface etched, but for through etching we generally recommend material from 0.011 to 1.5mm thickness.
The optimum temperature is approximately 45 degrees Celecius
Fortex PCB Shears and Guillotines are designed for cutting PCB Laminates, Plastics and thin sheet metals such as Aluminium and Brass.
Virtually all metals can be etched but some etch more easily than others, commonly etched metals include:-
Other steels including Tool Steel, Mild Steel, Carbon Steel
Various Nickel Alloys
Copper Alloys including Brass, Phospor Bronze, Nickle Silver
Aluminium and Aluminium Alloys (Care needs to be taken as the formation of Aluminium Oxide is Exothermic process so appropriate cooling coils need to be utilised)
Silver and Silver Alloys
Gold and Gold Alloys
Any shapes whether complex or simple can easily be generated. The only real limitation is the size of the smallest hole is generally 0.1mm when working with material that is thinner than 0.1mm. When working with materials that are thicker than 0.1mm holes can generally be produced with a minimum size equal to or greater than the thickness of the material.
Mounting films to the raster of the Fortex range of Laser Photoplotter must be carried out with considerable care ensuring after fixing the upper edge of the film to the drum, rotate the drum by hand and ensure the film is held tightly round the drum when fixed at the bottom. It is is also very important to check that the Emulsion side of the Photoplotter Film is facing the drum.
This can be caused by a number of factors the common ones are:-
- Poor density artwork, check the image is opaque.
2. Developer solution is to strong, dilute the developer.
3. Developer solution is to hot, check the temperature.
4. Resist has being exposed to stray white light, ensure the boards are correctly protected from stray white light during the processing stages.
No different types of Dry Film must be used for Ferrous and None Ferrous Metals due to the manner in which the Etching Takes place in the processing machine. These are listed on the website.
This is generally caused by the thicker material conducting heat away from the hot rollers of the Dry Film Laminator. To resolve this increase the roller temperature of the Laminator to give the correct exit temperature.
This can often be caused when the Specific Gravity of the solution exceeds 1.45. When Etching Ferrous Metal Plates the specific gravity of the solution should be 1.38 ‐1.42 . Allow the Pump of the spray Etching machine to run for 3-4 minutes before taking any measurements. Using a Hydrometer that covers the range 1.25-1.5 measure the Specific Gravity. If the Specific Gravity is found to exceed 1.45 dilute the solution with water to specific Gravity of 1.42. Also check the acidity of the solution detailed earlier in the FAQ list.
This is normally caused by the solution in the etching machine losing it acidity. This can be checked from time to
time by taking 5‐10ml of solution and adding it to 50 times the amount of water in a clear jug or beaker.
The ferric should look a clear to green colour, however if it appears to be cloudy with
particles floating in it then add 1% by volume 36% Hydrochloric Acid. When carrying out this test always allow the Spray Etching machine to run for 3-4 minutes before carrying out the test.
To over come this issue the artworks can be designed to have tabs (Silvers of Metal) so that through the complete etching process the parts remain in sheet from or we can offer mesh frames which the sheets of metal can be placed in prior to etching to catch all the small parts after etching.
This is generally caused by rinsing the Panel between passes, if multiple passes are required do not rinse the panel as the cold water shock the dry film emulsion and can cause it to shrink and lift.
The best away of preventing puddle formation is to use a spray etching machine with Horizontal Oscillation this will greatly minimise any puddle formation, which results in blocking oxygen contact with the Etchant as it is working on the material. This in turn can result in uneven etching.
This is generally caused by the solder temperature being to low (Increase the solder temperature), or the solder being contaminated.
Ferric Chloride Etches 1oz (35um) of copper in approximately 60-70 seconds in optimum conditions. With increasing saturation the etching time increases to over 3 minutes, under etching increases slightly. Theoretically Ferric Chloride will take up to 50g of Copper per litre, but this limit will not be reached as the Etching time will take to long. The Etching solution when spent should be neutralised and disposed of according to local in country regulations. We recomend changing th esolution when the Etching time has doubled.
When using Fortex Microtrak pre sensitised circuit boards a positive artwork must be used (ie. Black = copper) using UV translucent film, as the material is coated with positive working photoresist.
We recomend Ferric Chloride FeCl3 it has very good etching properties and is suitable for a wide range of applications and materials. Ferric Chloride has a high etching speed and ensures perpendicular walls. Ferric Chloride etches both warm and cold the optimum temperature being 45 degrees celcius.