Process for producing plated through-hole printed circuit boards having very small solder lands or no solder lands

• Main Authors: MERKENSCHLAGER, HANS-HERMANN, ZEIDLER, WOLFGANG
• Format: Patent
• Language: English; French; German
• Published: 27.09.1995
• Edition: 5
• Subjects: CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR; ELECTRICITY; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS; PRINTED CIRCUITS

The invention relates to a method for producing printed circuit boards with through-plated holes and very small solder lands, or no solder lands, around the through-plated holes. During the production of such printed circuit boards, especially in accordance with the Tenting method, there is a risk of the photographic film tearing off and etching medium penetrating into the metallised holes and damaging the metal sheathing. This can be avoided by producing a protective coating before the photographic film is applied. The invention is based on the aim of specifying a method in the case of which the advantages of the Tenting method can be maintained, but without a photographic film being used. This is achieved in that the printed circuit board (1) and the metallised holes (3) are provided with a protective film (4) which is resistant to alkaline etching medium but is soluble in acid. The protective film is then mechanically removed from the printed circuit board surface, and the printed circuit board is coated with photoresist (8). After coating and development of the photoresist (8), etching is carried out using an alkaline etching medium, and the photoresist coating (8) and the protective film (4) in the holes (3) are then removed by means of acid.