Smart devices are smaller and smaller ,but smarter. This has promoted the continuous progress of PCB technology，any layer HDI,laser drilling,back drilling ,etc. We must embrace new technologies and growing with it.
Below is an example what we did.it is a 4 layer board with 1.0mm,but the blind via is from L1-L2.
The blind via is only 0.075mm in the BGA pad. via in pad is must to do at the BGA area.
min hole 0.075mm, laser driling
blind via ,via in pad technology.
gap between hole edge to trace is only 0.128mm.
You may say,oh ,it is not a very difficult printed circuit. But,actually,the key technology is the gap between the hole edge to the trace is only 0.13mm (5mil).Usually,the gap should be more than 0.2mm,but there is no space and the trace is only 0.076mm (3mil). hole is 0.075mm, laser drilling
Storm Circuit made a lot of HDI circuit boards. Any layer HDI is the most complex circuit boards that the holes can be from any layer to any layers.We made an any layer HDI PCB for audiophile earphones. Any other HDI PCB is easier to do .Send us your HDI files now.
HDI--HIGH DENSITY INTERCONNECT Boards contain blind and/or buried vias and often contain microvias of .006 or less in diameter. They have a higher circuitry density than traditional circuit boards.
There are 6 different types of HDI boards, through vias from surface to surface, with buried vias and through vias, two or more HDI layer with through vias, passive substrate with no electrical connection, coreless construction using layer pairs and alternate constructions of coreless constructions using layer pairs.
The PCB specifications :
TG170,material:TU-768 (made in Taiwan) 1OZ
Black solder mask
Via In Pad,filled and plated to flat.
Blind vias :L1-L2,L1-L3,L1-L4,L1-L5,L1-L6,L1-L7