Coating apparatus – Solid applicator contacting work – Movably mounted applicator
Reexamination Certificate
2000-02-23
2002-02-05
Edwards, Laura (Department: 1734)
Coating apparatus
Solid applicator contacting work
Movably mounted applicator
C118S249000, C118S066000, C118S112000, C118S222000, C118S227000
Reexamination Certificate
active
06344087
ABSTRACT:
The inventions described below relate to a method for coating a board with liquid coating material, in particular for coating a basis board intended for circuit boards with liquid photoresist (photolacquer), as well as a board coating system for performing the method.
BACKGROUND OF THE INVENTIONS
In the production of multi-layer circuit boards, copper-laminated inner layers are normally coated with a photosensitive etch resistant. The etch resistant is exposed with an IC-original and following this, the circuit picture is developed. Since ever finer structures are required in circuit construction, it is necessary to apply the etch resistant very thinly and yet with high accuracy in the distribution of layer thickness. As clean an environment as possible is a prerequisite for this, since even the smallest particles as impurities on or in the applied etch-resistant layer can cause defects.
At the present time, there are two principal methods used for coating basis boards intended for use as circuit boards. In one, a dry film is applied to the basis plates by means of a carrier film. Following the exposure of the dry film the carrier film is then removed in order to enable the development of the board structure by means of an etching process. In another method the basis board is coated with liquid photo resistant by means of one or more coating rollers. Currently horizontal coating apparati with horizontally arranged coating rollers are employed for this purpose. Each coating roller rotates partially in a photoresist bath and is therefore uniformly moistened along its entire length with liquid coating material. The layer thickness is set by means of a doctor roller which is in contact with the coating roller and is adjustable with varying contact pressure against the coating roller. Opposite the coating roller a brace is arranged, thereby forming a pass-through gap therebetween. The brace can be formed as counterroller or as a second coating apparatus with horizontally arranged coating roller. Each board to be coated is supplied to the coating apparatus using a conveyer-belt or transport rollers and is gripped by its coating roller(s) and, if necessary, counterroller and is transported through the pass-through gap by these rollers while being coated. Following the coating the then coated board is gripped by a transport gripper and is then further transported to a next processing step, for example to the drying of the photoresist or to the exposure of the coated basis board. In the conventional coating system described for application of liquid photolacquer, disadvantages exist in that after coating of the board no uncoated free boarder exists so that a gripping apparatus of the transport gripper has to partially grip into the applied lacquer, whereby small lacquer flakes, so-called tinsels, can arise following drying of the lacquer upon opening the gripper. These flakes can lead to impurities on the basis board and hence to defects and to unusability of the later circuit board. Furthermore a skewing of the board can occur during the drawing-in of the base board between the rollers, something which is also detrimental to the accuracy of the coating. Since furthermore, the coating roller is at the same time also used for the transport of the basis board, a corresponding contact pressure against the board is required which also influences the coating thickness, so that its exact setting becomes on the whole more difficult. Furthermore a change of the board format causes problems in that the transport system must be configured to various widths of basis boards. This is because it is typically formed out of transport grippers which grip the board on opposite edges. The gripping of the board and its advancing to the rollers makes for further difficulties in that the boards cannot be correctly gripped by the gripping apparati or by the rollers, since these can exhibit warping. This is especially the case when the boards are intended for intermediate circuit layers and are formed very thinly. In production, this can lead to backups and/or to defective products.
SUMMARY OF THE INVENTIONS
The devices and methods described below provide a method as well as a board coating system of the type mentioned at the start, by means of which boards of the most different formats can be coated easily with improved quality and at the same time higher productivity.
According to the inventive method for the coating of a board with liquid coating material, in particular for coating a basis board intended for circuit boards with liquid photo resist, the board, in contact with a coating roller, is transported for coating past the latter by a transport apparatus. The coating roller here is rotated in a vertical orientation and the board, held by the transport apparatus on its upper edge in a vertically hanging position, is passed by the vertically oriented coating roller during coating. In addition to the production of circuit boards the method can also be employed for the production of other coated boards, like table or other furniture boards made of wood, steel or synthetic material as well as for construction and paneling boards.
With this method, boards of the most different formats can be coated error-free in a rapid and exact manner. The maximal board format is restricted only by the length of the coating roller whereas, with this as a starting point, any smaller boards are coatable without adaptation of the associated transport apparatus. This is because the boards can constantly be transported past the rollers at a constant height level, whereby the part of the board extending along the coating roller in its length is arbitrarily variable up to the maximum length of the coating roller. In that the boards, guided by the transport apparatus, are transported past the coating roller, a more exact coating is possible than if transport were to occur by means of the rollers themselves.
In order to achieve an even faster production process, the board in one preferred embodiment of the invention is in its supply to the transport apparatus, simultaneously gripped by the latter along the entire upper edge and/or in the removal from the transport apparatus the board is simultaneously released along its entire upper edge. To this end, the transport apparatus and an automatic board supply/or a board removal apparatus are formed accordingly.
Further, in order to ensure a smooth production process, the board which is to be coated is advantageously supplied to the transport apparatus through a funnel-shaped, tapered introduction shaft, thereby straigtening the upper edge of the board, which edge is to be gripped by the transport apparatus.
In order to further accelerate the production process during coating, following the coating process the board, gripped on its upper edge by the transport apparatus, is advantageously guided through a drying apparatus in a vertically hanging position in order to dry the applied coating material.
Particularly in the production of a circuit board, it is necessary that the photoresist applied to the board is cooled down to a suitable temperature prior to the exposure process. In order to accelerate the production process as a whole, following the coating process the board in the inventive coating method, gripped on its upper edge by the transport apparatus, is guided in a vertically hanging position through a cooling apparatus to cool the applied coating material. For the case that the board is to be coated on both sides, the board in the coating process is simultaneously coated on both sides by two coating apparati, which reduces the coating time.
To prevent the coating material from running off of the board, the coating material to be applied is preferredly set to a predetermined viscosity by cooling and/or heating.
The coating result can be further improved by heating the board which is to be coated prior to the coating process. To this end a heating source, for example an infrared heat radiator, can precede the coating apparatus. Furthermore the coating can be qualitatively improve
Crockett & Crockett
Crockett, Esq. K. David
Edwards Laura
ITC Intercircuit Handels GmbH
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