PTH VS NPTH
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On PCB boards, we?will see many holes with various?sizes, these PCB holes can be categorized into two types: PTH (Plating Through Hole) and NPTH (Non Plating Through Hole). The simplest approach to distinguish between PTH and NPTH in PCB is to examine the borehole wall for indications of plating.
What is?PTH?
Both the top and bottom layers of a PTH will always feature a copper pad that extends all the way to the hole’s rim. Pads having a diameter equal to that of the PTH’s inner diameter may also be present in the inner layers surrounding the PTH, depending on the application. This is a crucial criterion for all plated through holes, since it assures that the copper barrel on the hole wall will make a good electrical connection to all the pads during the electroplating process.
Some key characteristics of PTHs:
l Plated with copper to be conductive between layers
l Allow connections between layers in multilayer PCBs
l Used to create vias for changing routing layers
l Connect component leads to inner layers
l Allow higher component density versus single layer boards
What isnbsp;NPTH?
NPTHs or non-plated through holes are holes drilled in the PCB that are not plated with copper. They serve only a mechanical function like mounting components or providing heat sinks.
Since NPTHs are not plated, they do not electrically connect the copper layers. Instead they provide the following functions:
l Mounting holes for securing the PCB
l Holes for securing components like screws or bolts
l Slots or cutouts for components that extend beyond the board
l Heat sinks or thermal vias to dissipate heat
l Holes for alignment pins when assembling boards
Differences Between PTH and NPTH
The key difference NPTH versus PTH, is that NPTHs are drilled but not plated with copper, serving only a mechanical purpose.?PTHs facilitate electrical connections between layers while NPTHs serve only a mechanical purpose.
Recommended PTH/NPTH Design Practices
Here are some recommended design practices for working with PTHs and NPTHs:
l Minimize unused PTHs to reduce drilling costs
l Place components with PTH pins on same side to simplify routing
l Route critical signals first using PTHs/vias between layers
l Plan layer transitions to minimize number of vias
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l Use NPTHs for mechanical fixtures like mounting holes
l Provide sufficient NPTH clearance for mounting components
l Keep high-speed traces away from plated slot edges
l Verify final hole dimensions/locations against component requirements
FAQ for PTH and NPTH
What are some typical PTH use cases?
l Vias for changing routing layers
l Connecting component pads/pins to inner layers
l Creating plated slots or cutouts for edge mount connectors
l Connecting ground pins to bottom ground plane
l Providing shielding via fences on high-speed PCBs
What are some typical NPTH use cases?
l Mounting holes for securing PCB
l Component mounting holes (screws/bolts)
l Slots/cutouts for tall components
l Heat sinks/thermal vias for heat dissipation
l Holes for PCB alignment pins
l Non plated slots for edge mount connectors
Can a NPTH slot connect two traces on a single layer?
No, a NPTH slot cannot connect two traces directly?on a single layer,?since it does not have plating. A PTH slot is required to connect traces across a slot on the same layer.
How are PTH sizes defined in PCB design?
PTH sizes are defined by copper pad stacks attached to the hole on each layer. The hole size is drilled to fit within the pad stack annular rings. The pad stack diameters define the PTH size.
What determines the minimum annular ring size for PTHs and NPTHs?
For PTHs, the minimum annular ring size is driven by fabrication capabilities to achieve reliable plating adhesion. For NPTHs, annular rings are not required since holes are non-plated.
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