The TCD process mainly includes the following technical content:
A. Plug hole technology Before the screen printing thermosetting ink, the inner through holes should be filled with plugging oil. If the hole is not plugged first, a depression will occur at the orifice 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 heating. Now the PCB board cannot pass the thermal shock test. This shows that the quality of the plug hole is very important. Therefore, it is necessary to ensure that each hole on the board is 100% full.
B. Screen printing technology For TCD technology, screen printing quality is one of the keys. How to control the thickness of the printed ink to meet the customer’s requirements after it is fully cured, how to ensure the flatness of the ink, how to control the board’s printing ink, the expansion and contraction after baking, and how to control the warpage of the board surface, etc. The problem must be solved.
C. Surface roughening technology of ink layer The surface of the ink layer must be well roughened to ensure a good bond between the oil layer and the copper layer after PTH. After the circuit is made on the copper layer, the wire tension should be ≥1.0kg/cm.
D. Electroless copper sinking technology The electroless copper sinking on the surface of the ink layer is very different from the hole metallization of ordinary boards. The hole metallization (PTH for short) process of the ordinary board is to deposit a layer of copper on the insulating layer in the hole, so that the various layers passing through the hole are connected. The non-electrostatic copper on the surface of the ink requires that the positive blind holes and the surface are evenly deposited in the through hole. After thickening by electroplating, the line tension between the oil layer and the oil layer should meet the standard requirements, and after thermal shock (260℃) , There is no delamination after 20s). This requires that the initial reaction speed during electroless copper sinking is slow and the internal stress is small, otherwise it will be delamination after thermal shock.
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