TCD process mainly includes the following technical contents:
A. Plug Hole Technology
Before screen printing the thermoset ink, the through holes of the inner layer should be filled with plugging oil. If the hole is not plugged first, the hole will be dented after the ink is printed, and there will be air bubbles in the hole. The unevenness of the surface will directly affect the production of the circuit, and the gas in the hole will expand under the condition of heating, and now the PCB board cannot pass the thermal shock test. It can be seen that the quality of the plug hole is very important. Therefore, it is necessary to ensure that every hole on the board is 100% filled.
B. Screen Printing Technology
For TCD technology, screen printing quality is one of the keys. How to control the thickness of the printed oil to meet the customer’s requirements after it is completely cured, how to ensure the flatness of the printing oil, how to control the board’s printing oil, the expansion and contraction after baking, and how to control the warpage of the board surface are all very important.
C. Surface Roughening Technology of Ink Layer
The surface of the printing oil layer can only be well roughened to ensure a good bonding force between the oil layer and the copper layer after PTH. When the wire is made on the copper layer, the wire tension should be ≥1.0kg/cm.
D. Electroless Copper Technology
The full-board electroless copper on the surface of the printing oil layer is very different from the hole metallization of ordinary boards. The hole metallization (referred to as PTH) process of ordinary boards is to deposit a layer of copper on the insulating layer in the hole, so that each layer passing through the hole is conductive. However, the surface of the printing oil is completely non-electrodeposited copper, which requires positive blind holes and uniform deposition on the surface in the case of the via hole. , 20s) without delamination. This requires that the initial reaction speed of electroless copper is slow and the internal stress is small, otherwise it will be delaminated after thermal shock.
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