In the process of multilayer PCB production, there is a very tough problem---the black oxidation of the inner layer of the multilayer board. What black oxidation method is the most effective? And what is the effect of inner black oxidation? China PCB manufacturer SysPCB bring you relevant content introduction today!
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 prepreg and the inner copper foil.
PCB multilayer board black oxidation treatment
PCB multilayer board brown oxidation method
PCB multilayer board low temperature black oxidation method
The high temperature black oxidation method of PCB multilayer board will produce high temperature stress (thermal stress) in the inner layer board, which may cause the layer separation after lamination or the crack of the inner layer copper foil.
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 and there aren’t any other ingredients.
The general composition of blackening liquid:
Oxidizing agent sodium chlorite
PH buffer trisodium phosphate
Or basic copper carbonate ammonia solution (25% ammonia water)
1. 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：it can be measured by gravimetric method, generally controlled at 0.2---0.5mg/c㎡;
3. The significant factors that affect the peel strength through the relevant variable analysis (ANDVA: the analysis of variable) are:
①The concentration of sodium hydroxide
②The concentration of sodium chlorite
③Interaction between trisodium phosphate and immersion time
④Interaction between sodium chlorite and trisodium phosphate concentration
The best length of the acicular crystals of the oxide is 0.05 mil (1-1.5um), and the peel strength is also relatively large at this time.
The above is the relevant introduction about the black oxidation treatment of the inner layer of the multilayer PCB, and hope it can help you!