| 摘要 |
<p>Process comprising passing printed circuit plates between two rollers, one of which dips in a tin pool and transfers molten tin onto the plate, according to parent patent, is improved in that a highly elastic rubber strip (pref. a foamed silicone rubber) is placed behind a printed circuit plate provided with holes,. and is passed between the rolls together with the plate, so that the rubber is forced into the holes. When the pressure is released, the rubber recedes from the holes creating vacuum therein; this results in bursting of the tin layer freshly applied onto the other side of the plate, whereby plugging of the holes with tin is prevented. If the plate is provided with a great number of very small holes, into which the rubber cannot penetrate, the rubber strip can be inbued with a highly volatile liquid, which penetrates into the holes and evaporates therein at the tinning temp., thus breaking away the tin layer plugging the hole.</p> |
