Overview
Since introducing contact cleaning technology to the PCB / PWB industry over 20 years ago, Teknek have continued to provide innovative solutions for contamination control throughout the whole of a PCB / PWB production process. Electronics technologies have steadily become smaller and more complex and the problem of surface contamination more acute.
The Teknek contact cleaning principle is simple and highly effective - specially engineered elastomer rollers run in contact with the substrate to be cleaned (polyester artwork, FR4 panel, inner layers, press plate, polyimide etc) removing loose, dry contamination (dust, hair, lint, fibres, epoxy residue etc). The elastomer rollers run in contact with a specifically formulated adhesive roll, which removes and stores the contamination for later examination and disposal. Powerful anti-static systems are incorporated into most of our machines to prevent any re-attraction of airborne contamination to the cleaned product.
For the PCB manufacturer this translates to no more open and short circuits that need expensive rework, and scrap boards are kept to a minimum. This can result in quicker turnaround of orders, with higher yields and less need to over make, thus keeping costs down.
Details of the applications in which Teknek equipment is used in the PCB / PWB industry are shown under the 'Applications' tab above. If you have a dust sensitive process which is not included and are interested in improving your yield, reducing rejects or maximising your profit, please either call us directly or supply us with brief details in the 'Contact Us' section.
Click on the link below to view PDF
Flow chart showing where contact cleaning technology can benefit PCB manufacture
applications
A phototool is only of any use when it is clean and undamaged.
Phototools are either produced in-house, or via an external photoplotting bureau. In either case, it is likely that the artworks will have been produced, and hopefully packaged, in a clean room.
It is essential that the artwork is protected from scratching and other damage, as the image produced will exactly reflect the condition of the phototool.
Although no longer supplied by Teknek our very first product for the PCB industry, even before the contact cleaning principle, was the Protek range of artwork protection films. These optically clear, extremely thin films, are laminated to the emulsion side of the silver halide or diazo phototool and dramatically extend its life. Artwork protection film is polyester based, which means its dimensional stability is the same as the artworks it protects, so there is no chance of heat or humidity causing the film to deform.
Protection film can be laminated with the Protek Clean Machine Laminator (PCML). This unique machine combines the contact cleaning that Teknek is renowned for, with a robust cold-roll laminator. The artwork is simply fed into one end of this bench-top unit and exits free of contamination and protected from its environment, ready for use in primary or secondary image processing.
primary image
There are two clear goals in the primary image area:
- to apply an etch resist of consistent quality, either by dry-film lamination, in-line screenprinting or liquid photoimageable techniques.
- to expose the resist covered layer or panel to produce a clear image for etching.
Teknek cleaning technology allows you achieve these goals.
Goal 1 - For a piece of copper-clad laminate to be effectively covered in etch resist, it must be entirely free of contamination. It is likely that the laminate has passed through a brush or pumice station to key its surface to more readily accept the resist, but this cannot be viewed as a cleaning process, especially when so much of the residue removed at this area by Teknek technology is brush particles, pumice residue, and loose copper dust.
Only with these contaminants removed, can a perfectly flat and smooth etch resist be applied - avoiding tenting, coagulating and dry spots.
Teknek recommend the use of the CM8 Clean Machine (for one and two shift operations) in this area.
Goal 2 - The etch resist covered panel must now be exposed under ultraviolet light. The light is blocked by areas on the artwork that allow only part of the panel to be bathed in the UV.
The panel, artwork and glass or mylar frame must all be free of dust, hair, lint and fibres for the exposure process to succeed.
We recommend that the glass be cleaned with one of our Dust Control Roller (DCR) Range, which can also be used to clean the artwork when it is pinned in position.
Each etch resist covered panel should be passed though an auto-revesing CM8 Clean Machine (with auto-separation if the panels have a coverlay, such as Mylar), before being placed on the glass. This machine can also be used as an initial clean for the artworks before they are pinned into place.
Automatic Optical Inspection
Automatic Optical Inspection in widely viewed as one of the biggest bottlenecks in a PCB production facility. Using Teknek technology in this area, drastically reduces the important problem of false faults - where a board or layer is marked as a reject when in reality it is a piece of dust or hair that has caused the inspection system to flag a fault.
Teknek recommend the use of a CM8 Clean Machine in this area. Each panel is thoroughly cleaned before inspection so that any problems in the board are highlighted as they should be, rather than as a result of poor contamination control.
The CM8 should be uni-directional if the customer has an in-line inspection system, or auto-reverse if a manual AOI unit is used.
lay - Up
In a multiplayer facility, the opportunities to create expensive scrap boards is increased. A 16-layer board, once bonded, is economically unviable to repair should it prove to be faulty at electrical test. Trapped contamination on the layers, or the press plates, can be the source of significant wasted product.
Whatever the method of surface preparation for the inner layers, each should be passed through a CM8 unit before being laid-up. Equally, the press plates at the top and bottom of the book should also be completely free of contamination before the finished "sandwich" is placed in the bonding oven.
drill
After bonding, the multi-layer PCB is trimmed to size and drilled. The bare outside edges of the board, and the inner faces of the drilled holes, are then coated in copper by an electrolysis plating process, which connects each copper layer (the copper edges will be removed later in the process line). The board is then chemically cleaned.
Contamination on the surface of the panels can cause the drill bit to snap when drilling. This causes downtime and leads to scrap boards. Removing contamination from the board reduces the risk of breaking drill bits and gives higher yield.
This process leaves the board with two shiny copper outer faces, where the final circuit tracks will now be imaged and etched, after photo resist coating, by the use of another artwork / phototool and development under UV light, as described in Resist Lamination and Exposure.
solder mask
The application of a solder mask, or solder resist, must ensure that a clean, smooth coating of exactly the correct coat-weight. Dust, hair, fibres and epoxy particles anywhere on the board surface can cause a variety of problems with the solder mask coating.
It is essential that the mask adequately protects the areas of the board that are not designed to be tin-lead coated. Any break in the coating can allow the solder to deposit in the wrong place, leading to problems during the board assembly process in the end customer's facility.
It may be that a particle might be trapped under the resist in an area of the board where its presence might not affect the performance of the board in any way. However, at this stage, the board is almost complete, and many boards are rejected at this point simply due to them being aesthetically unacceptable.
For in-line applications such as curtain coating, spray application or dry film solder resist, Teknek recommend the use of the CM8 Clean Machine (for one and two shift operations). Manual screenprinting can be assisted with an auto-reversing CM8 or the Dust Control Roller range for smaller facilities.
Much as with primary image, it is then essential to clean the panel before exposure.
The panel, artwork and glass or mylar frame must all be free of dust, hair, lint and fibres for the exposure process to succeed.
We recommend that the glass be cleaned with one of our Dust Control Roller (DCR) Range, which can also be used to clean the artwork when it is pinned in position.
Each dry solder masked panel should then be passed though an auto-reversing CM8 Clean Machine before being placed on the glass. This machine can also be used as an initial clean for the artworks before they are pinned into place.
final test
Electrical probe jigs are used to confirm the correct operation of each track and circuit on the PCB.
Dust on the point of a probe will cause a short circuit, as the probe will not make direct contact with the pad. Installing a Clean Machine just before final testing, ensures accurate test readings.