First, plug hole process after hot air leveling.
This process is: plate resistance welding → HAL → plug hole → curing
Easy to cause plug hole ink pollute board. So many customers do not accept this method.
Second, the plug hole process before hot air leveling.There are 4 method:
2.1 Process: pre-treatment → plug hole → grinding plate → graphics transfer → etching → plate resistance welding
2.2 pre-treatment - plug hole - silk screen - pre-baking - exposure a development - curing
Advantages: open hole cover oil is good with wet film color.
Hot air leveling is to ensure that the vias are not on the tin and the hole is not hidden tin beads.
Disadvantages: easy to result in poor solderability.
2.3 pre-treatment - plug a pre-bake - development - pre-curing - plate resistance welding
But after HAL, it is difficult to completely solve tin beads in vias,so many customers do not receive.
2.4 plate welding and plug hole are at the same time to be completed.
The process is: pre-treatment - silk screen - pre-bake - exposure - development - curing
This process is short and the utilization of the equipment is high
In the curing, the air expansion will break through the solder mask, resulting in empty and uneven