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Source:互联网Author:qyadmin Addtime:2019-11-13 16:42 Click:

wood backer board for pcb drilling processing


Wood backup board

 
      wood backer board for pcb drilling is a backing board. designed for printed circuit board drill. recommended for drilling of high-tech printed circuit boards, multilayers and flex-rigid boards. In this airticle, Yueshan will point out the processing of wood backer board for pcb drilling

wood backer board for pcb drilling

Why use wood backup board for pcb drill?

 
Back up baord have follow feature:
 
- wood backup board excellent underlay board chipping. and free flowing extraction properties means lower risk of. flute blocking and drill breakage
 
-Reduced friction causes less wear on drill cutting edges, improving drill quality
 
-Reduced drill burr due to a smooth, hard and very thin overlay
 
-No phenolic or resin content to contaminate holes
 
-Excellent flatness and tight thickness tolerances
 
-Suitable for all drill diameters
 
-Usable on both sides without loss of quality. because of symmetrical build-up unique to 
 
     Printed circuit boards are becoming ever more complex. Stacking of etched copper. foil layers to form multilayer printed circuit boards are commonplace. but there is a trend to add more features and functionality. To do this, foil layers may have different thicknesses combined. with mixed material types. such as rigid or flexible layers.

     All this leads to increased topography of the printed circuit board surface. Interconnections between the copper foil layers done by drilling through. and piercing the foil, followed by a deposition of It is very important. that the drilled holes are free of defects that will become folds, crack. or seams in the plating. that could result in “opens” and circuit failure. dielectric surface are some examples of drilling problems. that lead to copper plating defects. Drilled and copper plated hole.
 
      As the copper metal electroplated around the burr. defects like plating folds, voids. and seams can occur These can lead to a crack in the copper plating causing an open circuit. a back-up material used to cut burrs by supporting the exit side copper. The back-up material placed under the PCB before drilling. Back-up material performs several important functions in PCB drilling: 
 
     First, the back-up acts as an offset lifting the PCB off the drill machine table. This gives the drill tool a material to drill in to after completely drilling through the PCB. This ensures complete drilling (penetration) of the PCB. while preventing damage to the drill machine table. Second, it provides support to the soft copper surface foil on the back side of the PCB. This support and the hard surface of the back-up prevent the copper from burring.
 
     Many PCB drill back-up materials will have a medium density wood fiber core. with a top coat of some more uniform material on the top and bottom sides. Because the drill tool does not penetrate more than ½ through the back-up, the back-up. used on one side then flipped and used a second time. Some top coat examples are aluminum foil, epoxy coated
 
      paper, liquid epoxy resin coat, melamine and acrylic. As stated above, the hard surface coatings on the back-up material. help prevent burrs, while the soft core minimizes drill bit wear. but, if the PCB is not flat. burrs can created when there is no contact between the exit side of the PCB copper. and the drill back-up material surface copper. Drilled with standard back-up. this PCB will need extensive manual rework to remove the burrs. and prevent plating defects.

wood backer board for pcb drilling processing

 
     In the manufacturing process the conforming. composite core used in combination with a shapeable surface coat. The coating must be able to bend and conform to the PCB surface while being hard enough to prevent copper burrs. One key feature of the conformal backup material is to not use a wood, metal or plaastic core. but one that contains air pockets such as low density paper, metal wool or polymer foam.

     This allows vertical displacement without lateral movement of the material. The top coat may be a laminated film or foil, or a dried/cured liquid such as epoxy, acrylic, phenolic or melamine. The key feature here is that it can bend and keep its shape in response to heat, pressure or both. The amount of heat and pressure must be enough for shaping, but low enough not to harm the PCB structure.

       Another key feature of the conformal backup is the top coat should have a room temperature. hardness of 30 to 90 on a Shore“D” Durometer scale. The core and the top coat bonded to one or both sides to make a composite. that attached to the PCB and shaped before drilling. It must do two things:. it cannot reduce the composites ability to conform. and it must not impart any contaminates into the
 
     PCB that will interfere with copper plating.  High topography printed circuits need a backing material to cut drill. burring to improve yields in downstream processes.
 
     The developed conformal back-up material has conformance characteristics. and performance properties that show the ability to cut drill. burring on high topography printed circuits. The materials used will not contaminate the drilled hole. and any debris from the drill process. removed using standardcleaning methods already used at the PCB manufacturer.



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