Conveyors: power-driven – Conveyor section – Endless conveyor
Reexamination Certificate
1999-06-16
2001-02-13
Ellis, Christopher P. (Department: 3651)
Conveyors: power-driven
Conveyor section
Endless conveyor
C198S803700, C198S803900, C198S575000, C198S605000
Reexamination Certificate
active
06186316
ABSTRACT:
DESCRIPTION
The invention concerns a process for precise electrolytic precipitating or removal of metals by slight etching and/or removal by etching up to the marginal area of printed-circuit boards and films in continuous-cycle plants.
Continuous-cycle plants permit the production of printed-circuit board and film panels with relatively low effort. Printed-circuit board panel is similar to the printed-circuit board raw blank. The same applies to printed-circuit film raw blank. This raw blank has a maximum width across the transport direction determined by the plant width. For carrying current to the printed-circuit board blank for electrolytic appliance of metal, these are usually contacted via contact clips connected to the negative pole of a direct-current source which take the printed-circuit boards at their edge in an electrically conductive manner. The anti-pole is built by soluble and insoluble anodes. After electroplating and after the post-treatment the printed-circuit boards are cut out of the printed-circuit board panel. Depending on the actual printed-circuit board size, one or several smaller printed-circuit boards are produced from one panel. For economic reasons, producers try to use the printed-circuit board panel as optimal as possible, i.e. close to the edge.
Among other factors, the quality of a printed-circuit board is determined by the plate thickness distribution on the surface and in the drill holes. Owing to engineering reasons, the plate thickness at the surface and in the drill holes in the marginal area of a panel strongly deviates from the plate thickness of the remaining surface areas. The thickness deviations may reveal positive as well as negative values. Among other items, the number of contact clips, their shape and insulation, the quality and the condition of the contact surfaces of contact clips, the geometry of the anodes and the shield elements as well as the distance of a panel to the subsequent one in transport direction of the continuous-cycle plant are influencing factors.
Particularly strong variations of plate thickness distribution exist in the area of electrical contact to the panel. For design reasons, the installation of shields is not possible to a sufficient extent here. The contact elements require the space which is necessary for metal deposition.
Publication DE 42 05 660 C1 describes a process for improving the plate thickness distribution in the marginal area of work pieces attached to cathode rails, e.g. printed-circuit boards, that are electroplated. Owing to the voltage drop in the cathode rail and/or in the work piece racks there are differences of electrical voltage between adjacent work pieces. These differences in voltage result in plate thickness differences in the marginal area of adjacent work pieces. These plate thickness differences are avoided by the temporary supply of current into the cathode rail and/or into the racks from opposite sides. This compensates the voltage loss in the rails and racks.
However, the optimisation of plate thicknesses on the work pieces has no effect on plate thickness variations in the direct area of clip grip positions.
EP-A-0 254 030 describes a horizontal continuous-cycle plant for electrolytic application of metal onto objects with board shape such as printed-circuit boards. Rotating contact elements in the form of clips grasp the boards. The clips are used for transporting the boards and—simultaneously—for supplying the galvanising current. The clips and also the boards have cathodic potential. In order to avoid a metallisation of clips, the electrically conductive clip is normally provided with an insulation layer apart from a small contact surface. For electrical and mechanical reasons, the clips have certain minimum dimensions. Several clips grasp one printed-circuit board panel.
A disadvantage of this appliance is the fact that the electrical field in the clip area is shielded in an unfavourable manner. This results in large plate thickness differences in the respective clip area. Moreover, the condition of contact surfaces, the electrical contact resistance and/or resistance of contact surfaces and the complete current conduction from direct current source to electric lines and screw connections determine the plate thickness. Under a clip nearly no metal is precipitated. In contrast to this, between two clips an excessive amount of copper is precipitated. These differences could not even be avoided by a marginal shield. The great plate thickness differences decrease towards the panel centre. The marginal area of the printed-circuit board panel—particularly from the clip area—cannot be used for the printed-circuit boards to be cut out. Owing to the strong variations in plate thickness, the quality of the adjacent areas is worse than the average. The width of the usable marginal area depends on the given admissible tolerance of the galvanising plate thickness. Especially with the fine conductor technology—that is used more and more frequently—this tolerance is low. In practice, owing to the clip influences, the unusable marginal strip width is between 25 and 50 millimeters. Despite cutting off this marginal area, the unfavourable coming together of several factors may cause the plate thickness differences on the remaining board to be as great that waste is produced. Additionally, there are considerable costs for cutting off the marginal areas. If there is, for example, a transport velocity of 1 meter per minute and an unusable strip width of 25 millimeters, the resulting daily loss in case of a two-shift operation is about 25 square meters.
DE 195 04 517 C1 describes a process and an appliance for galvanising board-shaped material to be handled in horizontal continuous-cycle plants. The material to be handled, preferably printed-circuit boards, is grasped by clips. The clips are used for supplying current and for transporting the printed-circuit boards.
With the help of sensors that scan the arriving material to be handled and under observance of the transport velocity a foresighted determination takes place as to whether material to be handled will be available at the gripping point of a clip or whether there will be a gap between two subsequent individual boards. In case of a determined gap, the clip will be controlled such that it does not close. This avoids a galvanising of the clip contacts which would lead to malfunctions.
A disadvantage, however, is the fact that the printed-circuit boards are grasped by clips without synchronisation at random positions in the marginal area of the boards. For this reason, the problem of the uneven plate thickness distribution in the clip range cannot be solved.
Therefore, the problem forming the basis of the invention is to avoid the disadvantages of the existing processes and appliances and, in particular, to considerably reduce the plate thickness differences on the printed-circuit board panel occurring during galvanising and especially in the area of the clips, and—thus—to increase the usable area of the panel (meeting the high quality requirements regarding plate thickness distribution) and to remarkably reduce the waste level (caused by plate thickness differences in the marginal area). There are also corresponding problems with the removal or thinning of metal layers during electrolytic etching.
The problem is solved by a process according to patent claim
1
and by an appliance according to patent claim
9
.
The process according to the invention for a precise electrolytic precipitation of metal layers up to the marginal area of printed-circuit board and printed-circuit film panels in a continuous-cycle plant includes the following process steps:
a) The panels are grasped in one or two opposite marginal areas by several contact elements driven in transporting direction.
b) The panels are grasped by the contact elements at different contact gripping points in several plant parts being arranged subsequently in transporting direction. This minimises variations of the metal plate thickness in the marginal area of the panels.
The app
Atotech Deutschland GmbH
Crawford Gene O.
Ellis Christopher P.
Paul & Paul
LandOfFree
Method and device for the precise electrolytic deposition... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for the precise electrolytic deposition..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for the precise electrolytic deposition... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2603006