GB2436169A

GB2436169A - Creation of copper filled blind vias using laser ablation in a double sided PCB

Info

Publication number: GB2436169A
Application number: GB0604588A
Authority: GB
Inventors: Vin Makwana
Original assignee: GARRY MYATT
Current assignee: GARRY MYATT
Priority date: 2006-03-07
Filing date: 2006-03-07
Publication date: 2007-09-19
Also published as: GB0604588D0

Abstract

Laser ablation of copper and epoxy/glass on a double sided laminate is performed from one side and stopped with high accuracy at the base of the bottom copper thus creating a blind hole. When metallised and electroplated, this connects the top copper to bottom copper but leaves a flat surface on one side of the printed circuit board. This is then advanced further by filling the blind hole with copper using a specially developed plating solution hence making the interconnect from top to bottom and leaving both surfaces flat.

Description

cREATION OF COPPER FILLED BLIND VIAS

USING LASER ABLATION IN A DOUBLE SIDED PCB

This invention relates to a method and process of producing a copper filled blind via within a double sided printed circuit board using laser ablation.

As electronics become greater in density and the use of fine pitch components push the boundaries of conventional design and layout techniques the use of laser and microvia (laser ablated hole) are becoming standard on HDI (high density interconnect) printed circuit boards.

The invention described is a method and process to enable laser ablation of copper and epoxy/glass on a double sided laminate from one side and stopping with high accuracy at the base of the bottom copper thus creating a blind hole and when metallised and electroplated connects the top copper to bottom copper but leaves a flat surface one side of the printed circuit board, this is then advanced further by filling the blind hole with copper using a specially developed plating solution hence making the interconnect from top to bottom and leaving both surfaces flat.

This invention gives a starting point for Increased development of microvia tower (microvia's placed on top of each other within a multilayer construction) but using copper as the filler at each stage as apposed to other non conductive or conductive matter. The advantage of using copper as the filler material is that other material has a different coefficient of thermal expansion that would cause stress fractures during printed circuit board assembly.

The invention will now be described solely by way of examples and with reference to the accompanying drawings in which: Figure 1) Shows the selection of the base material that's using a 0.1mm thick central core clad with 1 2im (top) /1 7im (bottom) Cu.

Figure 2) Shows the laser ablating from the 1 2iim Cu depth and controlled to stop at the base of the 1 Cu.

Figure 3) Shows the first pass of metallization of electroless Cu and panel plate.

Figure 4) Shows the flat pad on one side completed by imaging pattern and standard pattern plate of laser ablated holes followed by etching.

Figure 5) Shows the creation of the flat pad on the top and bottom of a double sided printed circuit board, the laser ablated holes are imaged with a button plate image followed by via filled Cu plate. To complete this process the double sided printed circuit board will undergo process 3) as highlighted above with the button plate image on selective vias only followed by Cu fill. Planerisation then takes place to remove excess Cu on surface layers to enable an even flat finish on both sides.

Figure 6) Shows the final process that's completed by imaging the pattern followed by standard pattern plate and etch.

Claims

CLAIMS

1. A creation of a copper filled blind via within a double sided printed circuit board allows printed circuit board designers to use via in pad for fine pitch and micro BGA's (Ball grid array)
2. A creation of a copper filled blind via within a double sided printed circuit board allows EMS (electronic manufacturing service) providers to use via in pad for fine pitch and micro BGA's without the added concern of air voids within the via in pad during printed circuit board assembly.

3. A creation of a copper filled blind via within a double sided printed circuit board allows greater product reliability due to copper density and conductivity.

4. A creation of a copper filled blind via within a double sided printed circuit board allows heat dissipation from the BGA component through a copper medium to base layer.