Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of substrate or post-treatment of coated substrate
Patent
1996-12-23
1998-09-08
Pianalto, Bernard
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of substrate or post-treatment of coated substrate
118224, 118227, 118249, 118641, 427 96, 427 98, 427211, 4273855, 4274432, 427508, 427559, 427595, B05D 306
Patent
active
058042563
DESCRIPTION:
BRIEF SUMMARY
SPECIFICATION
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a National Phase application of PCT/EP 95/22309 filed 14 Jun. 1995 and based, in turn, on German National applications P 44 21 966.0 filed 23 Jun. 1994; P 44 28 713.5 filed 12 Apr. 1994; P 44 314 218.7 filed 26 Sep. 1994; P 44 44 086.3 filed 12 Dec. 1994; 195 00 021.8 filed 3 Nov. 1995; 195 10 227.4 filed 23 Mar. 1995 and 195 16 193.9 filed 28 May 1995 under the International Convention.
FIELD OF THE INVENTION
The invention relates to a method of coating printed-circuit boards with an electromagnetically cross-linkable coating agent, preferably an agent cross linkable with UV radiation, the preamble of patent claim 1, as well as to a method of manufacturing multi-chip-modules from printed-circuit boards and to, a device carrying the methods.
BACKGROUND OF THE INVENTION
In the manufacture of printed circuits and, the so-called printed-circuit boards, for a conductor pattern, etch resists are applied in a silk screening process which corresponds to the structure of the desired conductor pattern. The etch resist is a lacquer system which, upon drying or exposure to UV radiation, gives rise to an adhesive-free surface resistant to the etching agent and which, after the etching of the laser pattern, can be again removed with so-called strippers in a 5% potassium hydroxide solution.
This type of conductor pattern generation is the most economical and therefore the most used in consumer electronics.
However this technique permits only the reproduction of conductor widths up to 300 .mu.m with sufficient precision. In commercial electronics for the last twenty years there has been a transition to the generation of the laser pattern photographically. For this purpose, dry film resists are laminated by rollers onto printed-circuit boards. The layer pattern is fixed by the use of a photo mask via UV radiation, whereby depending upon the process, either the conductors or the conductor-free regions are photopolymerized.
The pattern generation for etching technology requires only thicknesses of several micrometers. Since this cannot be realized with foils, photosensitive liquid resists have been applied to both sides of the board with profiled rollers. The kind and number of profile grooves determined the amount of material applied. As a consequence, the process is a profile-volume-defined application whereby the application rollers serve as metering rollers. The profile grooves enable a defined volume application with low viscosity and high application pressure.
After the generation of the conductor image, the circuit is provided with a solder-stop mask which leaves only the region to be soldered free. This solder-stop mask is also applied in a silk screening process and hardened thermally as well as by UV radiation.
For commercial printed-circuit board technology, this silk screening process has also been rendered no longer usable with increasing integration.
Thus, in EP A1 0002 040 a process for applying a liquid photopolymer in a curtain casting process has been proposed.
Furthermore, in DE 36 13 107 A1, resist color compositions are described which are applied by silk screening with an empty screen over the entire surface and which is fed structurably with UV radiation. Furthermore, dry film resists also are applied with laminating rolls with application of vacuum. The curtain casting process is limited by the high solvent content and thus cannot be used for thick layers.
The silk screen process has its limits in the technology of the screen so that no layer thicknesses of 10 .mu.m and also no layer thicknesses of 100 .mu.m can be applied in acceptable quality.
The dry film also cannot be applied in layer thicknesses of 10 .mu.m and thicker coatings cannot be used for the production of multilayer circuits of multi-chip-modules since they are not metallizable.
In WO 92/07 679 a roll coating process is described for one and both side coating of printed-circuit boards, especially with solder-stop lacquer. This process operates in a visc
Dubno Herbert
Kateshov Yuri
Pianalto Bernard
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