Why pads are used in PCB design

Thread Starter

Dadu@

Joined Feb 4, 2022
136
I am curious to know why PAD is used while designing PCB, what would be the disadvantages if PAD is not used. PCB has copper layer so why not solder the components directly without PAD.

sorry for the silly question
 

BobTPH

Joined Jun 5, 2013
5,259
The pad is the copper layer! We have just removed the copper surrounding it so that it is insulated from the rest of the copper layer other than the traces connected to it.

Bob
 

ag-123

Joined Apr 28, 2017
238
Because normally you would cover the PCB with solder mask.

If you don't have pads, then you have no where to connect !

It is possible to do without solder mask. The thing is if it is those modern chips with 0.5mm or closer traces, without that solder mask, you would be struggling with solder bridges all over the board when you try to solder them.
 
Last edited:

nsaspook

Joined Aug 27, 2009
9,993
Pads are a separate PCB component (usually added first in the design process before traces) for the physical attachment of parts to the PCB. It provides the needed electrical, mechanical, thermal, and physical registration (footprint alignment of position on the PCB) needed to securely connect devices to the traces of copper. The schematic to board design process (human or computer) creates the netlist of traces/interconnects from the geometry of the pads.

https://www.protoexpress.com/blog/what-is-pad-pcb-design-development/

The mechanical quality of each PCB pad is IMO usually an indication of the total PCB construction quality.
https://forum.allaboutcircuits.com/threads/male-header-pins-punching-through-pcb.165323/post-1458432

1655564718671.png
 

MrChips

Joined Oct 2, 2009
26,530
There are two essential components in a PCB connection, pads and traces.
Pads provide the electrical and physical solder joint on to which the component is attached.
Traces are the electrical connections between pads.
 

BobTPH

Joined Jun 5, 2013
5,259
I think his confusion was that he thought the pads were something put on top of the copper layer. He asked why we can’t solder directly to the copper layer, which indicates he did not know that the pads were made from the copper layer.

Bob
 

Thread Starter

Dadu@

Joined Feb 4, 2022
136
This is two layer PCB board. There may be vias inside the pads so do you see the vias anywhere on this PCB board?
 

ErnieM

Joined Apr 24, 2011
8,315
This is two layer PCB board. There may be vias inside the pads so do you see the vias anywhere on this PCB board?
Each pad in that board IS essentially a via. Termed a "thru hole" these provide a hole for the part lead, and the hole has a copper wall just as the layers do, as they are created (plated) at the same time.

When designing a board one typically starts from the schematic, then uses that to create the board. Using a typical design program before beginning the board each part on the schematic is given a footprint which describes how the mounting pads or mounting holes with pads will be used. Then on the board design side the footprints are placed to spot the parts, then the traces between are put down.

A typical 2 sided board has a center non conductive core, each side gets a layer of copper, plus copper in the holes, then a layer of something thin and non conductive (usually green) as the solder mask
 
Top