Continuing from the first part, we will further introduce the basics of HDI plating.
4.3.2 Plasma – Key Control Points:
4.3.3 Plasma – Quality Inspection:
4.4.1 Copper Deposition – Subprocess Function:
By using swelling to remove the drilling debris inside the holes, the charge inside the holes is adjusted to deposit activated palladium ions, which are then reduced to catalytically active metallic palladium under the action of reducing agents. A thin layer of copper is deposited on the activated hole wall substrate as a conductive layer for subsequent plating.
4.4.2 Copper Deposition – Key Control Points:
4.4.3 Copper Deposition – Quality Inspection:
4.4.4 Control of Plasma Dwell Time:The dwell time from plasma stripping to copper deposition must be controlled within 12 hours. If it exceeds 12 hours, plasma treatment must be reapplied.
For PTFE board material control, the dwell time from plasma to copper deposition should be ≤4 hours, and priority should be given to production after receiving the boards.
Timing starts after the first batch comes out of plasma (accurate to the minute), and the start and end times should be recorded on the time control card.
Plasma stripping rate requirement: 0.1-0.5mg/cm2
4.4.4.1 Requirements for Drag Tank Boards:The board thickness should be between 0.6-3.0mm, either pure substrate boards or AOI scrap boards are acceptable, with a clean appearance, no contaminants, and no exposed glass fibers; non-compliant drag tank boards cannot be used and must be replaced;
4.4.4.2 After exceeding the downtime, drag tank boards must be used as required to maintain the activity of the solution; when starting production for the first batch of each shift, backlight monitoring is required, and during mass production, backlight monitoring should be done every 2 hours;
For downtime of less than 30 minutes, use more than 5 drag tank boards;
For downtime of 31-60 minutes, use more than 10 drag tank boards;
For downtime of 61-120 minutes, use more than 20 drag tank boards;
For downtime of more than 2 hours, use more than 30 drag tank boards, prioritizing production of boards with through holes;
4.4.4.3 Considerations for Enhancing Copper Activity in Full Blind Hole Production: After continuous production of 60 panels of full blind holes, it is necessary to pair with the production of more than 20 panels of through hole boards or more than 5 panels of drag tank boards. Backlight monitoring for full blind hole production should be paired with the production of through hole material numbers or backlight test pieces, serving as confirmation for backlight replacement.
4.4.4.4 Control Method for Cap Copper Boards:For resin-filled hole processes followed by copper deposition processes, i.e., POFV cap copper boards, during production, every batch of 30 panels should be interspersed with more than 5 drag tank boards. Each batch should pair with the production of through hole material numbers or backlight test pieces, serving as confirmation for backlight replacement. Verify MI or physical samples (copper boards after resin-filled hole copper deposition) to identify cap copper boards.
4.4.4.5 Copper Deposition Scheme for High Aspect Ratio Boards (Aspect Ratio ≥10:1):The first copper deposition should be done with normal parameters, and the second should start placing boards from before the pre-soaking tank, with one piece sent for backlight confirmation for each material number.Visually verify and check MI to identify high aspect ratio boards (Aspect Ratio ≥10:1).
4.4.4.6 Three Major Rate Control Requirements for Copper Deposition Line and Backlight Control Requirements?
| Stripping Rate | ★ | 0.25±0.1mg/cm2 (Reference line speed 2.7±0.2m/min, equipment may vary.) |
| Micro-etching Rate | ★ | 1.2+/-0.4um |
| Deposition Rate | ★ | 0.6±0.2um |
| Backlight Testing | ★ | ≥9.0 grade |
| Dwell Time | △ | From copper deposition to flash plating: ≤4H |
| Automatic Solution Addition Calibration | △ | Measured value deviation from set value ±5% |
This is the second part, to be continued!!! More installments are coming, stay tuned!
Special Note: The above discussion is for reference only and serves as a starting point for further exploration! Each factory’s solutions/processes/equipment/product structures, etc., have various differences, and one must not rigidly apply these experiences; all effective improvement measures come from experimental data! As a professional quality of engineering technicians, one must “speak with data.”
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