DE3246774A1 - Protective mask for electroplating - Google Patents

Abstract

Heat-sealing mask tape for electroplating processes which comprises a markedly thermoplastic film carrier having an adhesive coating, characterised in that the film carrier is composed of a polymer based on polyvinyl chloride, ethylene-vinyl acetate and polymer plasticiser.

Description

Protective cover for electroplating

In electroplating processes - removal or application of metallic Layers - it is state of the art, the surfaces e.g. of printed circuit boards that are not to be subjected to the process of covering with masking tapes. These exist similar to the commonly used heat sealing tapes or self-adhesive tapes from one Carrier, which can be paper or foil, and an adhesive, heat- or pressure-activated one Mass uno have to meet some further requirements, i.

they should not and must not have a corrosive effect on the circuit boards do not release any water-soluble components that could have a negative effect on the electroplating baths can act.

After the electroplating process, the masking tapes have to peel off easily permit. Adhesive residues must be easily removable with solvents.

May be viewed as a disadvantage for self-adhesive cover films be that they are the higher and lower lying parts of a profile of a circuit board cannot follow due to a certain stiffness and that continues due to of tension in the cover system after a long period of time or with increased bath temperature the bond may lift off. Both have an undesirable effect penetration the electroplating baths in the area of the circuit board to be protected.

In the case of the heat-activated heat sealable tapes, the rigidity of the carrier does not play the role, as a thicker layer of adhesive and the effect of heat When rolling the cover film onto the conductor track, the mass plastically into the deeper ones Parts of the printed circuit is pressed in with a positive fit. The disadvantage here is that circuit boards with copper bars of approx. 70 Wm thickness also - adhesive thicknesses of need approx. 70 Wm. Accordingly, when the film is rolled on at the edge zones, the Cover squeezed out the thermoplastic adhesive, causing roller contamination of the laminator leads, and after the later peeling off of the cover film are larger Wash off amounts of adhesive residue.

The object of the invention is to eliminate the disadvantages listed and a cover film for electroplating with increased quality requirements To make available, which adapts to the structure of the surface stress-free and does not lift off, does not leave any capillary spaces free, no glue when rolling can emerge in the edge areas and no or only brief washing process requires.

Contrary to popular belief, it was found that the change has to be done less on the adhesive than on the supporting film.

If, from 80 ° C, a pronounced thermoplastic film with a self-adhesive or heat-sealable adhesive coated and at temperatures from 80-1200C with heated rubber rollers under pressure (Laminator) Laminated on a printed circuit board, the film adapts to the surface structures without tension at. Only a small amount of adhesive is required to fill any remaining cavities are provided, so that especially with thermoplastic binders only thin layers are required. Impurities from being squeezed out Tread glue. no longer succeeded on and because of the general mass reduction also the final washing process in solvents that may be necessary at short notice.

In the sense of the concept of the invention, a cover tape with a unstretched film carrier based on polyvinyl chloride about 60 to 75 ODs in particular about 67), ethylene vinyl acetate copolymer about 15 to 22%, especially about 17 ° Ó) and polymer plasticizers (about 10 to 15 ° Ó, especially about 14 OD) have proven successful. Included are polymer plasticizers e.g. polyesters made from adipic acid and butanediol.

The adhesives do not contain any special features and correspond to that State of the art. The bond strengths do not have to be particularly high because only slight mechanical loads occur. They are allowed to use the raw materials Do not contain any components that react with or become part of the electroplating bath solve, furthermore, the later soldering must not be adversely affected will.

Example 1 Cover film: Backing: 60 Wm film made from PVC, EVA and polymer plasticizer based on polyester.

Adhesive: 20 µm - self-adhesive on a poly-acrylate basis.

Test circuit board: 10 cm x 15 cm GRP epoxy board. Copper tracks, 70 jim thick, 1/64 inch wide, 1/64 inch spacing between copper tracks, copper tracks run parallel to the narrow side.

Sealing:: 5 cm x 15 cm wide cover film is placed on the test circuit board and with a heated double rubber roller (90 ° C) in two passes sealed with a running speed of 1.5 m / min.

Checking the flaws: The covered circuit board is inserted into a û, l ° Ó with a surfactant provided aqueous methylene blue solution (desiccator) inserted, vented under vacuum and ventilated again after a few minutes. In the event of errors in the gluing, the color peeling penetrates under the cover film.

Result:: No blue infiltration. Cover perfect.

Example 2 cover film: carrier. 30 Wm - polyester film adhesive : 20 jim - poly-acrylate-based self-adhesive.

Test circuit board 10 cm x 15 cm GRP epoxy board. Copper tracks, thickness 70 Wm, width 1/64 inch, copper tracks run parallel to the narrow side.

Sealing: 5 cm x 15 cm wide cover film is placed on the test circuit board placed and with a heated double rubber roller (90 ° C) in two passes sealed with a running speed of 1.5 m / min.

Check for imperfections The covered circuit board is cut into a 0.1 gÓ aqueous methylene blue solution (desiccator) with a surfactant inserted, vented under vacuum and ventilated again after a few minutes. If there are errors in the adhesive penetrates the paint solution under the cover film.

Result:: Color solution immigrated.

Cover not perfect.

Example 3 Cover film: Carrier: 60 Wm - film made of PVC, EVA and polymer plasticizer based on polyester.

Adhesive: 30 µm heat-activatable mass based on rosin and PVAC.

Test circuit board: 10 cm x 15 cm GRP epoxy board. Copper tracks, 70 µm thick, 1/64 inch wide, 1/64 inch spacing between copper tracks, copper tracks run parallel to the narrow side.

Sealing: 5 cm x 15 cm wide cover film is placed on the test circuit board and with a heated double rubber roller (90 ° C) in two passes sealed with a running speed of 1.5 m / min.

Testing of imperfections The covered circuit board is converted into a 0.1 Aqueous methylene blue solution (desiccator) with a surfactant inserted, vented under vacuum and ventilated again after a few minutes. If there are errors in the adhesive penetrates the color solution under the cover film.

Result: no infiltration.

Coverage flawless.

Claims (4)

Requirements Masking tape to be sealed under the influence of heat for electroplating processes, consisting of a pronounced thermoplastic film carrier with an adhesive coating, characterized in that the film carrier is made from a polymer based on polyvinyl chloride, Ethylene vinyl acetate and polymer plasticizer consists. 2. Masking tape according to claim 1, wherein the adhesive mass is self-adhesive is set. 3. Masking tape according to claim 1, wherein the adhesive mass is heat-activated is set. 4. Masking tape according to claim 1, wherein the polymer of the film carrier from 60 to 75 polyvinyl chloride, 15 to 22 o Ethylenvi'nylacetat and 10 to 15 m Polymer plasticizer based on polyester consists.