A.pcb stain / pitting
Stain procedure is to use chemical method to remove the greasy dirt on the inner copper resin. This greasy dirt was originally caused by drilling. Etchback is further deepening to the contamination is removed more resin, copper from the resin in the "outstanding", forming the "three combination" or "three combination" with the copper plating layer and improve the reliability of system interconnection. Permanganate oxidation of resin, and "etching". First of all need to be swollen resin, in order to facilitate the permanganate treatment, neutralization step can remove permanganate residue, etched glass fiber by different chemical methods, usually hydrofluoric acid. If improper contamination can be caused by two types of hole: in hole wall roughness of resin fouling may be in possession of liquid, can lead to "blowhole".
In the inner layer copper residue fouling can interfere with the excellent combination of the copper / copper plating layer, lead to "the hole wall pull off" (hole wall pullaway), such as in dealing with high temperature, or a related test, copper plating layer and hole wall separation. Resin separation may lead to pull-out and crack and hole wall copper layer on the hole. If in the neutralization step (accurate to speak 5, when is the reduction in potassium manganate residue is not completely removed may also lead to empty, the reduction reaction is often used reducing agent, such as hydrazine or hydroxylamine.

PCB B. drilling
The wear of drill or other improper drilling parameters may tear the copper foil and the dielectric layer, the formation of cracks. Glass fibers may also be torn, not cut off. The copper foil will it tear from the resin, not only depends on the drilling quality, the bonding strength depends on copper foil with resin. Typical example is: multilayer oxide layer and semi solidified sheet combination often compared to the dielectric substrate and copper foil with weaker, so most tear occurred on the surface of the multilayer PCB oxide layer. In metallography, tear occurred in copper foil relatively smooth side, unless the "reverse treated copper foil" (revers treated foil).
The oxide surface is not firmly combined with the semi - curing, and may lead to a worse "pink circle", which is the oxidation of copper in acid. Drilling hole wall roughness or hole wall roughness and pink ring will lead to the multi-layer combination of empty, called wedge void (wedge WoIdS) in the or blow hole blow holes, "wedge void" was initially in the binding interface, its name also hint that shapes, such as the "wedge", shrinkage cavity formation can usually be plating layer is covered. If the copper layer is covered on the groove, copper layer behind often water, later in the process, such as high temperature hot air leveling treatment, water (moisture) evaporation and wedge empty commonly occur together. According to the position and shape, it is easy to identify and separate from other types of cavity.

Catalytic procedure for C.pcb chemical precipitation of copper
Stain / etchback / electroless copper mismatch between each individual step and not optimized, is also worthy of consideration. Those who have studied the holes in the hole are strongly in favor of the unity of the chemical treatment. The traditional copper pre treatment order is clean, adjust, activate (catalytic), accelerate (after activation), and enter the clear (leaching) wash, pre soaked, completely suitable for Murpiy principle. For example, modifying agent and a cationic polymer electrolyte for the negative charge and the glass fiber is often a need to correct application to get the positive charge: adjustment agent is too small, the active layer and attached well; modifier too much, will form a layer of film leads to sink copper attachment is not good; so that the pulling out of hole wall. Inadequate coverage of the regulator, the most likely to appear on the glass head.
In Jin Xiangzhong, the empty openings in the glass fibers are not covered by copper, or no copper. Other causes of cavitation in the glass are: glass etching is not sufficient, resin etching over, excessive glass etching, catalysis is not sufficient, or copper sink activity is not good. Other factors that affect the coverage of Pd active layer on the pore wall include: activation temperature, activation time, concentration and so on. If the hole in the resin, may for the following reasons: to stain the steps of permanganate residue, plasma residues, adjustment or activation is not sufficient, Shen copper bath activity is not high.