Blackening Treatment Of Inner Layer Of Multilayer PCB Board
In the process of multi-layer PCB production, there is a very difficult problem-the blackening of the inner layer of the multi-layer board. What black oxidation method is the most effective? And what is the effect of inner blackening? Today, the editor specially invited technical personnel with many years of experience from Taike to bring you relevant content introduction!
Blackening treatment of inner layer of multilayer PCB board
Black oxidation of the inner layer: passivate the copper surface; improve the surface roughness of the inner copper foil, thereby improving the adhesion between the epoxy resin board and the inner copper foil.
Black oxidation method for general inner layer treatment of PCB multilayer board:
PCB multilayer board black oxidation treatment
PCB multilayer board brown oxidation method
PCB multilayer board low temperature blackening method
PCB multilayer board adopts high temperature blackening method, the inner layer board will produce high temperature stress (thermal stress), which may cause the layer separation after lamination or the crack of the inner copper foil;
1. Brown oxidation:
The black oxidation treatment products of PCB manufacturers' multilayer boards are mainly copper oxide, rather than the so-called cuprous oxide, which is some wrong statement in the industry. Through ESCA (electro-specific-chemical analysis) analysis, the binding energy of copper atoms and oxygen atoms on the oxide surface and the ratio of copper atoms to oxygen atoms can be determined; clear data and observation analysis show that the blackened product is copper oxide. Contains other ingredients;
The general composition of blackening liquid:
Oxidizing agent sodium chlorite
PH buffer trisodium phosphate
Sodium hydroxide
Surfactant
Or basic copper carbonate ammonia solution (25% ammonia water)
Blackening treatment of inner layer of multilayer PCB board
2. Relevant data
1. Peel strength (peel strength) 1oz copper foil at a speed of 2mm/min, the width of the copper foil is 1/8 inch, and the tensile force should be more than 5 pounds/inch
2. Oxide weight (oxide weight); can be measured by gravimetric method, generally controlled at 0.2---0.5mg/cm2
3. The significant factors that affect the tear strength through the relevant variable analysis (ANDVA: the analysis of variable) are:
①The concentration of sodium hydroxide
②The concentration of sodium chlorite
③The interaction between trisodium phosphate and immersion time
④The interaction between sodium chlorite and trisodium phosphate concentration
The tear strength depends on the filling of the resin to the oxide crystal structure, so it is also related to the relevant parameters of the lamination and the relevant properties of the resin pp.
The length of the acicular crystals of the oxide is 0.05 mil (1-1.5um) as the best, and the tear strength is also relatively large at this time.
The above is the relevant introduction about the blackening treatment of the inner layer of the multilayer PCB, I hope it can help you!
