FRP Precursor Surface Treatment for Thin Copper Foil Lamination
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Solution Overview
Problem
Conventional methods for producing printed circuit boards with thin copper foils (40 µm or less) are prone to light spots and press scratches due to surface waviness from the reinforcing substrate, and the two-stage hot-press process decreases productivity and fails to adequately suppress light spots.
Innovation Solution
A method involving interposing a FRP precursor between releasing films or laminating it with thermosetting resin films to reduce surface waviness to 12 µm or less, followed by hot-pressing, which allows for a single-stage lamination process and reduces light spots in the metal-clad laminate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the copper foil thickness is reduced to 40 μm or less to meet weight and size requirements, then the weight and size of the printed circuit board are reduced, but the surface waviness from the reinforcing substrate causes light spots and press scratches on the copper foil
Solution Approach 1:
The invention applies preliminary action by performing a surface treatment process on the FRP precursor before lamination to reduce surface waviness to 12 μm or less. This pre-treatment eliminates the surface irregularities that would otherwise cause light spots and press scratches on thin copper foils during subsequent hot-pressing, allowing the use of thin copper foils without quality defects.
Solution Approach 2:
The invention introduces an intermediary measure by implementing a surface treatment process that acts as a mediator between the reinforcing substrate and the thin copper foil. This treatment creates a flattened intermediate surface that prevents the transmission of surface waviness from the FRP precursor to the copper foil, resolving the conflict between using thin copper and maintaining surface flatness.
2Manufacturing precision
If a two-stage hot-press process is used to suppress light spots by holding at softening temperature, then light spot formation is reduced, but the lamination time increases and productivity decreases
Solution Approach 1:
The invention applies preliminary action by pre-reducing the surface waviness of the FRP precursor to 12 μm or less before hot-pressing. This eliminates the root cause of light spot formation, allowing the use of a simple one-stage hot-press process instead of a complex two-stage process, thereby maintaining high productivity while achieving excellent suppression of light spots.
Solution Approach 2:
The invention extracts the surface treatment step from the hot-pressing process itself. By separately treating the FRP precursor surface beforehand, the invention removes the need for the complicated two-stage hot-press process with its holding period, achieving both light spot suppression and high productivity through process simplification.
3Productivity
If conventional lamination is performed without surface treatment on the FRP precursor, then the process is simple and productivity is high, but surface waviness causes light spots and press scratches on thin copper foils
Solution Approach 1:
The invention applies preliminary action by implementing surface treatment on the FRP precursor before lamination. This pre-treatment reduces surface waviness to 12 μm or less, enabling the use of thin copper foils without light spots or press scratches while maintaining a simple one-stage hot-press process for high productivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively suppresses light spots and press scratches, enhances the tent property of the metal foil, and maintains industrial productivity by eliminating the need for a two-stage hot-press process, even with thin metal foils.
Implementation Method 1
the prepreg is heated without applying a pressure until the thermosetting resin therein reaches its softening temperature
Implementation Method 2
until the thermosetting resin therein reaches its softening temperature
Implementation Method 3
then the pressure is applied after the resin is softened, namely, the hot-press process is carried out by dividing it into two stages
Data Source
Figure 1(a)~2(d)
AI summary
Provided are: an FRP precursor capable of providing a metal-clad laminate having small surface waviness and reduced number of a light spot, even if thickness of a metal foil is 40 µm or less; a laminated plate including the FRP precursor; a metal-clad laminate having a metal foil on the laminated plate; a printed circuit board having a circuit pattern formed on the metal-clad laminate; a semiconductor package including the printed circuit board; and methods for producing them. The FRP precursor has the surface waviness of 12 µm or less on both surfaces thereof.