- Mar 02,2019
PCB circuit board
As the demand for electronic products increases, so does the structure. Due to the space limitations of the PCB board, the circuit board is also gradually "evolving" from a single layer to a double layer to a plurality of layers. So what is the difference between the multi-layer PCB circuit board and the double-layer PCB circuit board in the manufacturing process?
The multi-layer pcb circuit board is a printed circuit board which is laminated and bonded by alternating conductive pattern layers and insulating materials. The number of layers of the conductive pattern is more than three layers, and the electrical interconnection between the layers is realized by the metallized holes. If a double panel is used as the inner layer, two single panels are used as the outer layer or two double panels as the inner layer, and two single panels are used as the outer layer, the positioning system and the insulating bonding material are laminated together, and the conductive pattern is pressed. Designed to interconnect, it becomes a four-layer, six-layer printed circuit board, also known as a multi-layer PCB circuit board.
Multi-layer pcb circuit boards are generally fabricated from epoxy glass cloth-clad laminates, and the manufacturing process is based on the process of plating double-panel holes. Its general process is to etch the pattern of the inner layer first. After the blackening process, the prepreg is added according to the predetermined design for lamination, and then a piece of copper foil is placed on the upper and lower surfaces, and sent to the press for heating. After pressing, a "double-sided copper clad plate" with an inner layer pattern is prepared, and then a numerically controlled drilling is performed according to a pre-designed positioning system. After the drilling, the wall of the hole is subjected to etching treatment and desmear treatment, and then the process of printing the circuit board by double-sided plating is carried out.
Compared to the general production process of multi-layer boards and double-panels, the main difference is that the multi-layer board adds several unique process steps: inner layer imaging and blackening, lamination, etch and desmear. Certain process parameters, equipment accuracy and complexity are also different in most of the same processes. For example, the inner metallization connection of the multi-layer board is the decisive factor for the reliability of the multi-layer board, and the quality requirement of the hole wall is stricter than that of the double-layer board, so the requirement for the drilling is higher. In addition, the number of stacks per hole of the multi-layer board, the speed of the drill bit and the feed amount during drilling are different from those of the double panel. The inspection of finished and semi-finished products of multi-layer boards is also stricter and more complicated than that of double-sided boards. Due to the complicated structure of the multi-layer board, it is necessary to use a uniform temperature glycerol hot-melt process instead of an infrared hot-melt process which may cause excessive local temperature rise.