What can cause porous tin layer during plating

Hello! I am an engineer of a semiconductor plant. We have two plating issues:
1. We use Nickel sulphamate to deposit Ni on the sliver surface. Sometimes the Nickel layer was discontinuous. The caused bad solderbility of our products. And the right side(working area) of the Hull Cell ⇦ huh? panel was too thin even nonplated. I can see the right side was deposited much slower than the left side.
2. We use Tin Sulphonate to get tin layer. Recently we found the Tin layer was porous and easily damaged. The tin at the top of the parts will peel off to expose Ni layer after silghtly damaged by the electrical test machine.

I'd llike to get your help about what can cause above two issues? And how to improve the plating layer.

Hi Cathy,

In both the cases the deposit is not complete due to the starvation of the metal Ions ( Ni and Sn)in the plating solution. Try to increase the concentration of the Electrolyte and try plating at optimum current density.

keep a small positive voltage while entering in the plating bath

or

Activate in 10% nitric acid with thorough rinsing. Use only depolarised anodes for sulphamate.