PCB Depth control routing technology is the stepstair or groove shaped by partial routing in printed circuit boards(PCBs) manufaturing.It have great advantages in PCB assembly as the special shape of depth routing.

  • Use the step stair of PCB edge make card slot is favor for PCB fixed and installation.
  • It can avoid cold soldering as siphonic effect use NPTH stepstair slot.
  • Use the stepstair in middle of PCB apply in special module application,and degrade the height of PCB assembly,achieve refinement and miniaturization.
  • Use special size NPTH stepstair as resonant cavity of microwave signal,degrade signal loss and other special function.

There are two main methods of manufacture stepstair .

Depth control routing:

PCB depth routing

Filling and embedding cushion material.

PCB depth routing

We main introduce the control depth of stepstair and manufacture capability for depth control routing. And learn the control of adhesive,the pattern of stepstair rim and the hole’s reliability,size capability of stepstair.

The study for Capability

Mechanical milling:

For the stepstair PCB of mechanical milling,the precision can be +/-4mil is very high as equipment factor.As the stepstair slot is always in the depth of 0.2-0.4mm at some layers, it’s impossible to keep milling to particular layer, there have depth tolerance as the control principle and mechanical precision. At present,main use two ways to control the depth of milling in stepstair milling process.

  1. Optical rule control Z axis height:through Optical rule induce and control Z axis height to finish depth control routing.

PCB Optical rule control Z axis depth

  1. Through milling tool and copper layer form a closed loop path to measure and control the height of principal axis down to finish depth control routing process.The copper layer can be surface layer or particular layer. The precision of this method can be achieve to +/-15um,so the copper thickness of stepstair minimum is 30um,it risk copper remain at bottom layer after depth milling process.

pcb depth routing


Filling and embedding cushion material.

Filling cushion material to make depth routing for that stepstair is in middle of PCB center, main control the resin flow at side wall,slot bottom and notch,ensure resin flow stability at bottom, resin flow homogeneity at side wall and no resin flow at notch.

PCB depth routing-2

For this kind of stepstair milling PCB, all use FR4 materials and CORE+CORE to lamination. The prepreg thickness 20mil, the chip thickness 20mil. There are different size of stepstair,minimum 20x20mm,maximum 200x200mm,the depth milling is 1.0mm.