ML PCB manufacturing – Pattern Plating, Solder mask, Surface finish

ML PCB manufacturing

Pattern plating

ML PCB manufacturing

Pattern plating is a DC electro plating process.

The drilled holes, which are made conducting in the PTH process, are built up to 25 microns, to act as good conductors.

In this process, the copper area exposed during photo printing also gets plated. Hence, the process is called “pattern plating”.

PCB Solder Plate

ML PCB manufacturing

At the end of the pattern plating, the panels (ckt pattern) are plated with tin metal. This platted tin act as etch resist, to protect plated copper while removing unwanted copper (copper below DFPR) in the subsequent process (alkaline etching)


Alkaline etching

ML PCB manufacturing

The resist which was acting as plate resist is stripped (similar to inner layer stripping), exposing the unwanted copper.

The unwanted copper is etched to obtain the required circuit pattern

Tin stripping

ML PCB manufacturing

After etching, the tin coat (which was acting as etch resistant during etching) is stripped off.

Solder Mask

Solder mask is “a coating material used to mask or protect selected areas of a printed  wiring board from the action of an etchant, solder or plating”

Functions of Solder resists

ML PCB manufacturing
  • Reduce solder bridging and electrical shorts during assembly
  • Protect PWB circuitry from handling damage.
  • Provide an environmental barrier
  • Fill space between conductor lines and pads with material of known dielectric characteristics.

Hot Air Solder Levelling

ML PCB manufacturing

In this process solder (an alloy with 60% tin and 40% lead, or 99% tin – lead free solder) is applied in the areas where components are mounted, I.e. where connectivity for the electrical components is required.

Solder protects copper from oxidation and give better solderability at the time of assembling the boards with components.

Gold Plating

ML PCB manufacturing

Electro less Nickel gold

  • This is an alternative process to HASL
  • For surfaces such as contacts or tips that normally receive heavy wear, the use of nickel under gold will greatly increase the wear resistance,

Electro Gold plating

  • Gold is an excellent resist for etching. Along with this gold has good electrical conductivity, tarnish resistance and solderability after storage.
  • Gold can produce contact surfaces with low electrical resistance.
  • In spite of its continued advantages, the high cost  of gold has restricted its major application to edge connectors (tips) and selected areas



In Legend the identification symbols are screen printed on the board to aid the assembly operation

Carbon Printing

Carbon Printing
  • Carbon coating is a surface finish process an alternative to HASL or ENIG.
  • Carbon has a special property of having a very high mechanical resistance and a low electrical resistance.
  • The specials property of carbon finds use in Key pads such as Phones, ATM machines, key boards etc


  • Fabrication describes many mechanical operations that bring the PCB to its final dimensions, create specified slot, grooves bevels or chamfers
  • Milling the PCB to its final dimension and slot  creation is done in routing
  • In ‘Scoring’, ‘V’ grooves are machined on opposite sides of the panel to sufficient depth to allow the user to break apart boards from the panel after assemble.

Bare Board testing (BBT)

Bare Board testing (BBT)
  • Finished PCB without any components mounted is called as Bare Board
  • Bare board testing is done to check the electrical integrity of the PCB.
  • In BBT the boards are checked for opens, shorts, voids and isolation
  • Jigs are used to test the boards. Jigs are     the test fixtures are usually constructed by drilling a piece of nonconductive material with the same pattern as the drilled holes, along with the pad (SMT) pattern. Spring loaded metal pins are inserted in the drilled holes of the testfixture to make contact with the correspondingpoints on the PCB to be tested. The opposite ends of the metal pins are connected by wire  to the test equipment.



BBT machine

Final Inspection

  • The final step in the manufacturing process is a visual inspection of the finished PCB.
  • In final inspection PCBs are checked for correct mechanical dimensions and are visually examined for overall appearance and other cosmetic parameters

AQL (Acceptance Quality Level)

The AQL is a visual inspection of the finished PCB after the Final Inspection in sampling basis.

In AQL PCBs are checked for correct mechanical dimensions and are visually examined for overall appearance and other cosmetic parameters.


The final step in the manufacturing process is a packing, after the AQL the boards are packed as per the specification.

Cerra Systems Printed Circuit Board Fabrication capabilities support high-frequency PCB, High-temperature Boards, Thick PCB, ultra-thin PCB, heavy copper PCB, Metal Core PCB, HDI boards with Blind Vias, Buried Vias, Micro Vias, Embedded passives, bonded heat sink, Impedance Control, Depth control drilling, Back drilling, Edge Plated PCB, Bump Pads, cavity with ledge, Via on pad and stacked micro-Via technology.

CerraSystems –

HDI PCB ,  Rigid Flex PCB,  RF PCB 

Electronics Manufacturing Partners:

Argus Systems (AESPL) –

PCB,  PCBA,  Cable Assembly,  Box Build,  Testing