HDI Printed Circuit Board
                     WWW.PNCONLINE.COM
HDI 
PRINTED 
CPINRBOC
CUIT 
A IRncD
WHAT IS HDI 
PRINTED CIRCUIT 
BOARD
HDI stands for High Density Interconnect. HDI 
PCBs have finer traces and trace spacing, 
laser drilled micro vias and higher connection 
pad density. Its two chief advantages are that 
it permits the use of fine pitch BGAs and it 
reduces the number of PCB layers required 
because the finer traces and smaller vias 
allow more circuitry in a smaller area.
NARROW TRACE WIDTHS MEAN HIGHER CIRCUIT 
DENSITY
At PNC standard PC Board fabrication 
uses a minimum trace width of 5 mil, 
with a 5 mil space between traces 
(5/5mil) PNC’s HDI trace widths can 
be as narrow as 3 mil with 3 mil 
spacing.  
These finer traces allow 160% more 
traces in the same real estate. 3/3mil 
spacing will also allow two traces to 
escape between pads of a standard 
BGA, meaning less PCB layers are 
needed to fan out the pins from the 
BGA.
MICROVIAS ARE THE ENABLING TECHNOLOGY 
FOR HDI
Narrow trace widths used in HDI PC Board are a result of the gradual refinement of 
photolithography and etching technology.  Microvias on the other hand, are a 
revolutionary innovation driven by the development of high powered lasers that can 
be controlled accurately enough to ablate a 3 mil hole through the surface layer of 
copper and underlying laminate, without damaging the underlying layer of copper.
The Printed Circuit Board design at PNC take advantage of this by locating the power 
and ground layers at the top of the stack up.  Since all active components access 
power and ground, sometimes through multiple pins, having the power and ground 
layers directly below the component layer allows all those connections to be made 
directly by microvias.  This leaves the component layers and layers beneath the 
power and ground layers completely unobstructed for signal routing. This has the 
added advantage of reducing parasitic capacitance because it eliminates the circuit 
stubs caused by plated through holes.
Two sided boards are typically fabricated 
with a combination of through holes and 
microvias.   Though holes can be drilled 
just through the core, connecting the 
stacks on the top and bottom of the board 
from the lowest layer, or through holes 
can be drilled through the entire stack 
directly connecting the traces on the top 
and bottom component layers.
HDI PCBs are a necessity when using fine 
pitched BGAs, but they can also reduce cost 
on PCBs without fine pitched BGAs because 
of the reduced layer count.  On your next 
PCB design services, talk to the experts at 
PNC.  They can help you determine if HDI 
technology is can reduce your PCB cost by 
reducing layer count and shrinking the PCB 
size.
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PHONE
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