overview

For  the past 20 years the world's leading bare board PCB manufacturers have utilized Teknek contact cleaning systems to remove board level contamination before critical processes - providing them with increased yields and low rejection rates.

As one of the final PCB processes before supplying to the CEM / OEM is a routing operation there can often be contamination left on the board surface which can reduce the solder paste print quality or even damage the stencil.  Even if the boards are cleaned before packaging, re-contamination can occur as they are shipped (often thousands of miles around the world) before being unpacked and loaded onto a surface mount line which is generally not in a cleanroom environment

Contamination or dust on the board can greatly affect assembly. It can enter the manufacturing process at any stage and can directly affect the yield, reliability and process of a surface mount assembly line. Contamination as small as 1 micron can lead to poor solder joints, open circuits, short circuits or poor joint integrity leading to a field failure.

Starting with a clean substrate helps increase production, as residues only become more difficult to remove with thermal and chemical processing.

The Clean Machine principle is a two part transfer process. A special elastomer roller gently cleans the surface of the board removing loose particulate contamination, down to 1 micron. The contamination transfers from the board to the high surface energy of the elastomer roller. A high coat-weight adhesive roll rotates in contact with the  elastomer  roller, constantly collecting the contamination. A powerful anti-static system prevents re-contamination  of the board by airborne particles.

Cleaning the stencil on a regular basis, to remove excess solder paste and any other contaminants, is recognised as a necessary maintenance procedure for maximum print quality . Often this contaminant is brought into the stencil on the board surface . Removing dry unattached particles from a bare board immediately before solder paste or any adhesive application reduces solder defects, increases production yield and product reliability.

The DCR Handroller system can also be used as a final clean on the underside of the stencil after the automatic cleaning process.

Applications

As electronic assembly requires finer and finer pitches for surface mount, TAB and MCM, the demands placed on the manufacturer are ever-increasing. Contamination on the surface of the board is a major factor in downtime, poor quality and low yields.

Placing components onto a PCB for surface mount technology requires the application of solder paste. Stencil printing of solder paste is a critical step in the surface mount process. The quality of the print is directly correlated to the process yields. Any contamination, or dust, that is drawn into the stencil aperture directly effects the quality of printing. As the pitch and aperture get smaller for fine pitch technology the size of the particulate contamination becomes increasingly detrimental to the manufacturing process.

Application of adhesive paste by the needle must be precise, to ensure accurate positioning and that the appropriate quantity is applied. To apply the paste, pressure is passed down the nozzle. Once paste is released, a small backward suction can draw up any particulate on the board, or stencil, creating a blockage. The lines must then be stopped while the nozzle is changed. The removal of particulate, directly before printing, reduces the downtime experienced through blocked adhesive nozzles, as well as, reducing the frequent cost of replacement.

A specially formulated elastomer roller runs in contact with the surface of the substrate. The dry, unattached particles are transferred from the material by the roller onto our engineered adhesive roll. The adhesive roll can then be purged, removing contaminants from the process.