Method of manufacturing a multilayer printed wiring board with copper wrap plated hole
View Patent ↗Printed circuit boards have circuit layers with one or more via filled holes with copper wraps and methods of manufacturing the same. An embodiment of the present invention provides a method to enhance the consistency of the wraparound plating of through-hole vias of printed circuit boards with (requiring) via filling to provide extra reliability to the printed circuit boards and enables the designers and/or manufacturers of printed circuit boards to design and manufacture boards with relatively fine features and/or tight geometries.
1. A method of manufacturing a printed circuit board or a sub-component of the printed circuit board having a plurality of circuit layers with at least one hole for interconnecting copper patterns on the different circuit layers of the circuit board or the sub-component of the circuit board, the method comprising:
laminating the plurality of circuit layers with each other to form the circuit board or the sub-component of the circuit board with a first solid copper layer and a second solid copper layer respectively as both outermost layers of the circuit board;
drilling the hole into the laminated circuit layers;
de-smearing the drilled hole;
metalizing the circuit layers with the de-smeared hole to metalize the hole;
coating a first photo resist on both the outermost layers;
patterning the first photo resist on the circuit layers with a first photo dot to expose the metalized hole;
electrolytic copper plating the metalized hole with an electrolytic plating solution to plate the metalized hole to a desired copper thickness;
stripping the first photo resist;
planarizing the plated first photo dot around the plated hole down to a level substantially the same as the level of the at least one of the first solid copper layer or the second solid copper layer;
selectively removing a portion of at least one of the first solid copper layer or the second solid copper layer to form a clearance to correspond to the plated hole;
metalizing the circuit layers with the plated hole and the clearance to metalize the clearance around the hole;
coating a second photo resist on both the outermost layers;
patterning the second photo resist on the circuit layers with a second photo dot to expose the metalized clearance and the hole;
electrolytic copper plating the hole with the electrolytic plating solution to plate the hole to a desired copper thickness in the metalized hole and with a copper wrap continuously wrapping from the hole wall onto an outer surface in the clearance around the hole;
stripping the second photo resist;
filling the copper plated hole with a via fill material;
curing the via fill material in the via filled hole;
planarizing the via fill material and the plated copper wrap in the clearance around the plated hole to a level substantially the same as the level of the at least one of the first solid copper layer or the second solid copper layer; and
forming a conductive image to cover the planarized hole with the planarized copper wrap.
2. The method of claim 1 , wherein the metalizing the circuit layers with the de-smeared hole comprises electroless copper plating the de-smeared hole, and wherein the metalizing the circuit layers with the plated hole and the clearance comprises electroless copper plating the clearance and the plated hole.
3. The method of claim 1 , wherein a circumference of the clearance is bigger in size than that of the drilled hole, and wherein a circumference of the second photo dot is not smaller in size than that of the clearance.
4. The method of claim 1 , wherein the laminating of the plurality of circuit layers comprises laminating a plurality of substrates with each other, each of the plurality of substrates being interposed between one and a corresponding one of the plurality of circuit layers, wherein the plurality of substrates comprise a resin, and wherein the removing of the portion of the at least one of the first solid copper layer or the second solid copper layer to form the clearance comprises selectively etching the portion of the at least one of the first solid copper layer or the second solid copper layer down to the resin.
5. The method of claim 1 , wherein the laminating of the plurality of circuit layers comprises laminating a plurality of substrates with each other, each of the plurality of substrates being interposed between one and a corresponding one of the plurality of circuit layers, wherein the plurality of substrates comprise a resin, and wherein the removing of the portion of the at least one of the first solid copper layer or the second solid copper layer to form the clearance comprises selectively etching the portion of the at least one of the first solid copper layer or the second solid copper layer without exposing the resin.