1.1 Use aluminum plug hole, curing, grinding plate after the graphic transfer
This process uses a CNC drilling machine to drill aluminium plugs that have holes to be plugged into, to make screens, to make plugs, to ensure that the plug holes are full, plug ink is used to plug the ink, and thermosetting inks are also available. Their characteristics must be high hardness. The shrinkage of the resin is small, and the bond strength with the hole wall is good. The process flow is: pre-treatment → plugging → grinding plate → pattern transfer → etching → board surface solder mask
With this method, it is possible to ensure that the through-hole plug hole is flat, hot blast leveling will not have oil quality problems such as oil burst, hole edge oil fall, etc. However, this process requires one-time thickening of copper to make the copper thickness of the hole wall reach the customer's standard. Therefore, the requirements for copper plating on the entire board are very high, and there is also a high requirement on the performance of the grinding board machine to ensure that the resin on the copper surface is completely removed and the copper surface is clean and is not polluted. Many PCB manufacturers do not have a one-time thick copper process, and the performance of the equipment does not meet the requirements, resulting in the use of this process in the PCB factory.
1.2 Direct screen printing plate surface solder resist after plugging holes with aluminum
This process uses a numerically controlled drilling machine to drill aluminum pieces that have holes to be plugged into, and a screen plate is made. The screen holes are installed on the screen printing machine, and the plug holes are not allowed to park for more than 30 minutes. The surface of the plate is screen-printed with a 36T screen. Process flow: pre-treatment - plug hole - silk screen - pre-baking - exposure - development - curing
This process can guarantee that the cover hole cover oil is good, the plug hole is flat, the wet film color is the same, after the hot air leveling can ensure that the conduction hole is not on the tin, the hole does not contain tin beads, but it is easy to cause the ink in the hole after curing. Pads, resulting in poor solderability; after hot-air leveling, the edges of the vias are foamed and degassed. Production control using this process is difficult, and process engineers must use special procedures and parameters to ensure plug quality.