What is the correct resin smearing method

2019-11-29 15:41Writer: qyadminReading:

PCB   Resin Smear 


      A thin layer of resin known as ‘resin smear’ or ‘epoxy smear’ that formed. between the copper interface and the PTH wall which creates a poor bond. between plated copper and the hole wall including the inner plane copper interface
 
      Resin used in the PCB fabrication is a thermosetting polymer. If the drill bit is dull and speed/feed ratio is not optimized. during drilling, the drill starts to extrude or punch through the PCB material. The resin becomes soft owing to excessive heat produced . and dragged across copper interfaces and the hole wall 
 
        Resin Smear is the effect of resin adhering to the inner copper layer in the hole wall.

        After cross section, the coating measured (as shown in the figure below). where resin smear detected. The smear value may be the ratio (%) based on the width of resin smear to inner layer copper. that has adhered to the hole wall structure as demonstrated in the determine below.
        If the evaluation using stack drilling has done, all the panels measured.
        The maximum smearing points measured around final hit hit counts. 
 
                                          What is the correct resin smearing method

                                  Resin smear ratio[%] = B/A x 100

                        A: Inner copper layer thickness [µm]

                        B: Resin smear width [µm]
 

pcb smear  manufacturing

 
    In printed circuit board (PCB) manufacturing. plasma technology can deliver higher uniformity and reproducibility. than chemical or mechanical processes and help improve reliability. It is efficient, cheap and environmentally benign. Plasma processing increases the surface energy of advanced materials. including fluoropolymer, providing excellent lamination. and wettability for plating through-holes without the use of wet chemicals. It also allows metalization to the inner layers by removing resin smear created. in the drilling process and removes carbon byproducts from blind vias.
 
     Desmear & Etch Back - The mechanical drilling of. vias in multi-layer PCBs creates a residual resin that smears. along the via walls, impeding metalization of the electrical connections. After drilling, resin removal from inner layer posts. required to ensure reliable electrical contact. Traditional methods of etching and desmearing are often not effective. due to the capillary effect. present with wet chemicals, and the limitations related. to the use of advanced board materials. In contrast, plasma removes epoxies, polyimides. high Tg blends, mixed materials, and other resins in standard and high aspect ratio panels.
 
    Non-Stick Surface Activation - The Nordson MARCH plasma process can change fluoropolymer surfaces. and desmear resins to prepare hole walls for electro-less copper or direct metalization. Surface activation for double-sided. and multi-layer fluoropolymer through-hole boards is necessary to increase surface wettability.
 
     Carbon Removal - Plasma treatment removes carbon from both conventional through-hole board vias. and blind vias. Laser-formed vias often produce a carbon by-product that prohibits electro-less adhesion. Carbon that mixes with epoxy or polyimide resin. and becomes trapped in the vias must removed before metalization. Plasma cleaning. removes the carbon from both conventional through hole board vias and blind vias. used on boards. where component space restricted.
 
     Inner Layer Preparation - Plasma alters the topography and wettability. of inner printed circuit board layers to promote adhesion. Cover-coated inner board layers that contain flex materials. with unsupported polyimides have smooth surfaces. that are difficult to laminate. Plasma alters the topography and wettability of the inner layers to promote adhesion. by allowing thin layer processing through use of flex clips. Other chemical processes are not as effective. it is difficult to control the amount of material removed. and unsupported polyimides are inert to most chemicals.
 
     Residue Removal (Descum) - Plasma treatment removes resist residue from PCB inner layers. and panels without affecting the circuit pattern. It also removes residual solder mask bleed. from lands for better bonding and solderability. Resist residue sometimes remains after developing fine pitch circuitry. If the residue is not removed before etch, the board can short circuit. Plasma removes resist residue from inner layers. and panels without affecting the circuit pattern. It also removes residual solder mask. bleed from lands for better bonding and solderability.

 


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