PNC’s step by step guide to PCB Design
                     PNC’s step by step 
guide to PCB Design 
component 
placement
www.pnconline.com
A schematic is an abstraction, a representation of an ideal circuit.  A 
PCB Assembly, on the other hand, is a complex mechanical assembly.  
All the components in the circuit design must fit within the physical 
boundary of the PCB.  
The designer must locate and place hundreds of components subject 
both to the mechanical constraints of the product design and the 
manufacturing process while not introducing electrical noise into the 
circuit.
It can seem overwhelming to someone new to the PCB layout process.  
Fortunately, there are some simple guidelines used by the designers at 
PNC that will help break the layout task into manageable pieces. 
Initial component 
placement considerations
Start by identifying the mechanical constraints on the component 
location. The Printed Circuit Board size and shape will be defined 
by the overall product configuration. Typically, the product’s 
mechanical design will define the location of the connectors, the 
keep-out zones and the locations of the heat sinks. The initial 
mechanical layout of the PCB is often an iterative process defined 
during design and early prototyping.
The next step is to divide the PCB into functional modules to 
simplify routing and grounding.  This will help minimize noise 
between power components, high speed digital components and 
analog components.  Switching power supplies are particularly 
noisy, so the power supplies and their associated components 
should be grouped together as far as possible from noise sensitive 
sections of the circuit. While defining the location of the modules, 
be aware that high power components will need heat sinks, which 
may limit placement options.
Locating active components
Once the edge components 
are placed and functional 
areas of the Printed Circuit 
Board are defined, the next 
step is to locate the BGAs, 
quad packs and other large 
high pin count components. 
The room needed to fan out 
their pin counts is going to 
drive the locations of all the 
components around them.
Locating Passive 
Components
As a follow on to locating the active components, the bypass or 
decoupling capacitors on the power pins should be located as 
close to the IC as practical to minimize the parasitic inductance. If 
more than one capacitor is being used PNC recommends that the 
lowest value capacitor should place closest to the power pin.  
If components will be located on both sides of the PC Board, the 
bypass capacitors are often located on the opposite side, directly 
under the power pin. If possible, each power pin should have its 
own bypass capacitor.
Layout of double-sided 
boards
Double sided PCBs, PCBs with 
components on both sides, are 
expensive to produce, but 
may be necessary when real 
estate on the PCB design is 
tight, and when the overall 
product form factor is more 
important than PCB cost.   A 
double-sided PCB is more 
expensive because it will need 
to pass though the pick and 
place machine and reflow 
oven twice. 
Schedule a Design Review 
with your PCBA manufacturer
These are some general 
guidelines to aid in component 
placement used by the PCB 
designers at PNC.   However, 
they are just guidelines.  The 
best way to ensure that the 
printed circuit board assembly 
can be manufactured reliably 
is to have the layout reviewed 
by the people who will 
manufacture it.
PNC’s designers can review 
your design to help reduce 
production cost and improve 
yield and reliability.  Contact 
PNC today to schedule a 
review.
Contact Details
Address: Phone: (973) 284-
PNC INC, 1600
115 East Centre St. Email: 
Nutley, NJ, 07110 [email protected]
Website: www.pnconline.com