is PUMEX 2000 Surface Preparation
Printed Circuit Board Surface Preparation
Highly efficient scrubbers of modular design for surface preparation prior to dry-film lamination or other printing operations. This answers the increasingly challenging requirements in the production of fine line high quality circuitry, where the absolute absence of any contaminants from surface and holes must be guaranteed, whilst the surface topography must be perfectly suitable for good adhesion of all coatings.
- The best surface preparation
- Removal of all contaminants and foreign particles
- Modular design
- Maintenance-free construction
- Main Uses
The major suppliers of dry-films and solder masks emphasize the need to prepare the board surface by scrubbing (with nylon brushes and a slurry of pumice or of other abrasive powders) prior to coating so as to ensure consistent quality of the surface in almost all environmental conditions irrespective of the time lapses between the various manufacturing steps of the printed circuit board. The nature of the residues left on the boards by the base material suppliers or by other processes in manufacturing, are continuously evolving. This means that the mechanical action of the brushes tangent to the board surface is a must to otain repetitive yields. The copper surface is perfectly cleaned and the resulting topography is the most suited for adhesion thanks to the peak-rich area obtained. This method of preparation is the industry standard. The narrow processing window of other methods, such as chemical cleaning or jet scrubbing, do not at all guarantee the same consistency in all the different conditions which may arise (see inside for more details). The 2000 SERIES scrubbers have been developed in the light of new approaches to producing fine line circuitry. Surface preparation plays the most important role out of all the manufacturing steps to be performed. The versatility of this cleaning method and the wide range of abrasive powders which can be employed in these scrubbers allow to control and adapt the surface profile (roughness) according to the standards required by today’s and tomorrow’s technology.
- Modular Design
This offers the possibility of combining various modules to build processing lines to comply with different requirements and special requests.
Both basic machines (Pumex 2000 and Pumiflex 2000) include:
- Input conveyor with a suitable number of rollers.
- Scrubbing: the boards are processed on both sides by three pairs of fast rotating nylon brushes sprayed with abrasive in suspension in water. This suspension is recirculated by a pump in a suitable tank where it is automatically and constantly stirred.
- Pre-rinse chamber.
- Three stage washing with water sprays.
DESCRIPTION OF ADDITIONAL MODULES
- PVC Acid Rinse
- Ideally suited for an acid rinse to remove heavy oxides, conversion coatings, chromates, etc.
- Ultrasonex for hole cleaning
- Ultrasonic energy is applied to water through which the board are conveyed in immersion.
- Water Blast
Four upper and four lower knife-shaped nozzles, in staggered position, very close to the boards, oscillate to cover the whole conveyor width and thoroughly clean the holes with strong jets of water at pressure of 115 bar/1.670 p.s.i. (for the 24” version) or 90 bar/1.300 p.s.i. (for the 30” version). The strong mechanical action thus applied to the boards (=impingement) ensures complete through-hole washing.
The main features of these innovative modules are: lint-free design (no cotton or other materials which may leave foreign particles on the boards), total filtration of the air and sealed construction so that no dust or other particles can accumulate inside (see leaflet “SHD/A Drying” and “rolly shd/a” for further details). Front view (all doors removed) of a high production surface preparation line including: PVC Acid Rinse Module at input for the removal of deep oxides and other heavy contaminants, PUMILEX-2000 brush scrubber, Ultrasonic/Wa
- The CLEVERBRUSH System
The purpose of this system is to allow brushing of thin materials without damage. This conveyor system consists in pairs of pinch rollers and guides to support the foils d during
transportation. However there are no guides or grids underneath the brushes which would be quickly worn out by the strong combined action of nylon and abrasive. The sheets are placed onto the input conveyor one after the other, with their edge parallel to the direction of transportation.
- A series of photocells detects the leading edge of sheets and the first pair of rollers are automatically started and stopped in order to provide the necessary spacing between one sheet and the next.
- An encoder connected to the conveyor drive system constantly monitors the travelling of sheets throughout the machine and the signals corresponding to sheet length and sheet position are sent to a Programmable Logic Controller (P.L.C.)
- Each pair of brushes is driven by a self-braking motor which starts and stops in the proper direction and at the proper time under control of the P.L.C.
- When the leading edge of a thin foil reaches the brushes, these rotate in the direction of transportation so that the foil is conveyed between them.
- The action (=friction) of the brushes in the direction of transportation would damage very thin foils, as soon as their trailing edge leaves the pinch rollers before the brushes. Therefore, before this happens, brushes stop and immediately reverse the direction of rotation. In this way the sheet is always under pull by the brushes themselves.
- After trailing edge leaves the brushes, these reverse once more, ready to process the next piece.
- All above steps are repeated in the same manner for each board, upon reaching each of the three pairs of brushes.
- The inversion of rotation of each one of the three pairs of brushes takes place in three different positions along the same board in order to avoid non-uniform scrubbing.