CNC PCB micro drilling Exit board

  • Composition

     

    Exit board for micro pcb 

          High density CNC pcb drill exit board is a high density wood fibreboard with no added resin. suited as an exit material for pcb drilling. and routing single sided, double sided. and multilayer printed circuit boards. 

    micro drilling PCB Method

            The drilling machine is a preprogrammed Computer Controlled (CNC) machine. The drill takes place based on the XY coordinates fed into the CNC system. The spindles rotate at a high RPM and ensure an accurate drill hole in the PCB. When the spindle rotates with a rapid speed, heat generated. due to the friction between the hole wall and the spindle. This melts the resin content on the hole walls and results in a smear of resin. Once the required holes drilled the exit and entry panels discarded. This is a small gist of what goes happens on the shop floor.
     
          Single-sided or double-sided PCB will drilled after getting on the production line. Multi-layer board will drilled after pressuring layers. By classification of the function, different drilling holes. can divided: parts hole, tool hole, through the hole. blind hole, Buried hole. In recent years, electronic products need to be light. Thin. Short. Small. Fast. So we need better drilling technology, like, laser burning holes, photosensitive holes.
     

    Mechanical Drilling Layer
     

    Drilling processing needs these parts: drilling bit, backup board, Entry board.
     

    Laser drilling holes

     
    With the development of electrical technology, we need to make the vias smaller. and smaller, While the mechanical tool will broken if the size is too small. Laser drilling aimed to drilling the holes smaller than 0.2mm.
     
    When engineers design PCB with BGA, HDI boards, we need to make microvias with laser drilling.
     
    dril pcb hole
     
    Laser drilling is much more expensive than mechanical drilling. We recommend you to use Φ0.3mm drilling holes to save your money.

     micro drilling pcb

     
         As the packing density of the through holes in the PCB assembly line increases. the demand for smaller holes increases . Two main technologies that used to produce accurate. and repeatable holes of microns in diameter are mechanical drilling and laser drilling. The through hole diameters can range from 50-300 microns. and run about 1-3 mm deep using these PCB drilling techniques.
     
          The drill press consists of a high-speed spindle, which rotates at speeds of about 300k RPM. These speeds are essential to produce the required accuracy. for micron-level drilling on the PCB.
     
          To maintain accuracy at high speeds, the spindle makes use of an air bearing and a direct drill bit assembly. which held by a precision collet chuck. Additionally, the vibration of the tip of the bit controlled within a 10-micron range. To maintain the exact position of the hole on the PCB. the drill mounted on a servo table, which controls the motion of the table on the X and Y-axes. A tunnel actuator used to control the motion of the PCB in the Z-axis.
     
           As the pitch of the holes in the PCB assembly line is  decreasing. and the demand for higher throughput is increasing. the electronics to control the servo may lag behind at some point. The use of laser drilling to create through holes. for manufacturing PCBs helps reduce. or drop this lag and is the next generation’s need.
     
        Laser drills used in the PCB fabrication process consist of a complex set of optics. which used to control the pinpoint accuracy of the laser, required to make a fine hole.
     
          The size (diameter) of the hole to drilled in the PCB controlled using the aperture of the setup. and the depth of the hole controlled by the time of exposure. Also, the beam split into various energy bands to further provide control. and precision. A moving focal lens used to. concentrate the energy of the laser beam exactly at the drilling location. A Galveno-sensor used to move and position the PCB with high speed and accuracy. Galveno sensors capable of switching at speeds of 2400 KHz are currently. used in the industry.
     
    Additionally, a novel method known as the direct exposure technique. can also used to drill holes in the circuit board. This technique based on the concepts of image processing. where the system increases the accuracy. and speed by creating an image of the PCB and converting that image into a position map. The position map is then used to align the PCB under the laser for the drilling process. 
     
    Advanced research in image processing algorithms and precise optics will. further improve the throughput and yield of PCB fabrication. and high speed drilling used in the process.
     

  • Description

     

    Drilling PCB material details


    Thickness and Tolerance 2.5 +/-0.15mm
    Density >980 Kg/m3
    Bending Strength >45 N/mm2
    Warpage <0.6% across the diagonal Delivery Specification
    High density pcb drill exit board supplied in cut panels. and position hole to customer requirements 
     

      

    cnc pcb drill

     
    Unlike the etching and plating process. the drilling process doesn’t have a fixed duration. The drilling time varies in the shop floor depending on the number of holes to drilled. This is what happens behind the curtains in PCB manufacturing unit.
     
    Two significant aspects to considered in the drilling process:
    The aspect ratio
    Drill to copper clearance (Drill to the nearest copper feature)
    Aspect Ratio
    Aspect ratio is the ability to plate copper inside the holes(vias). The copper plating of the interior part of holes is a tedious task. when the diameter decreased and the depth of the hole increased. This requires a plating bath with a higher throwing power so that the liquid could gush into the tiny holes.
     
    Aspect ratio (AR) = (Depth of the hole/ Diameter of the drilled hole)
     
    The aspect ratio is 10:1 for through holes and 0.75: 1 for microvias.
     
    Drill to Copper
     
    The drill to copper is the land clearance between the edge of a drilled hole to the nearest copper feature. The nearest copper feature can be a copper trace or any other active copper region. This is the deciding factor since even a small deviation will lead to cirucit disruption.
     
    Smallest clearance = annular ring width + solder mask dam clearance
     

     

    cnc pcb drill

     
    Unlike the etching and plating process. the drilling process doesn’t have a fixed duration. The drilling time varies in the shop floor depending on the number of holes to drilled. This is what happens behind the curtains in PCB manufacturing unit.
     
    Two significant aspects to considered in the drilling process:
    The aspect ratio
    Drill to copper clearance (Drill to the nearest copper feature)
    Aspect Ratio
    Aspect ratio is the ability to plate copper inside the holes(vias). The copper plating of the interior part of holes is a tedious task. when the diameter decreased and the depth of the hole increased. This requires a plating bath with a higher throwing power so that the liquid could gush into the tiny holes.
     
    Aspect ratio (AR) = (Depth of the hole/ Diameter of the drilled hole)
     
    The aspect ratio is 10:1 for through holes and 0.75: 1 for microvias.
     
    Drill to Copper
     
    The drill to copper is the land clearance between the edge of a drilled hole to the nearest copper feature. The nearest copper feature can be a copper trace or any other active copper region. This is the deciding factor since even a small deviation will lead to cirucit disruption.
     
    Smallest clearance = annular ring width + solder mask dam clearance
     

    cnc pcb drill

     
    Unlike the etching and plating process. the drilling process doesn’t have a fixed duration. The drilling time varies in the shop floor depending on the number of holes to drilled. This is what happens behind the curtains in PCB manufacturing unit.
     
    Two significant aspects to considered in the drilling process:
    The aspect ratio
    Drill to copper clearance (Drill to the nearest copper feature)
    Aspect Ratio
    Aspect ratio is the ability to plate copper inside the holes(vias). The copper plating of the interior part of holes is a tedious task. when the diameter decreased and the depth of the hole increased. This requires a plating bath with a higher throwing power so that the liquid could gush into the tiny holes.
     
    Aspect ratio (AR) = (Depth of the hole/ Diameter of the drilled hole)
     
    The aspect ratio is 10:1 for through holes and 0.75: 1 for microvias.
     
    Drill to Copper
     
    The drill to copper is the land clearance between the edge of a drilled hole to the nearest copper feature. The nearest copper feature can be a copper trace or any other active copper region. This is the deciding factor since even a small deviation will lead to cirucit disruption.
     
    Smallest clearance = annular ring width + solder mask dam clearance
     

  • Product Advantage

     
    Classification of Holes
    The drilled holes classified into Plated Holes (PTHs) and Non-Plated Holes (NPTHs).
    The plated holes (PTHs) are the signal carrying conductive vias. that establish interconnection between the different layers in the PCB.
     
    The non-plated holes (NPTHs) are non-conductive. These used to hold the components in position during the PCB assembly process. The component mounting holes are NPTHs. There is no tolerance level for these holes since the components won’t fit in if the hole size is too small or large.
     
    A rule is a rule even for a hole
    Non-Plated Through Hole (NPTH)
    Finished hole size (mimimum)= 0.006″
    Edge to edge clearance (from any other surface element) (minimum)= 0.005″
    Plated Through Hole (PTH)
    Finished hole size (Smallest) = 0.006″
    Annular ring size (Minimum)= 0.004”
    Edge to edge clearance (from any other surface element)(minimum) = 0.009″
    Drilling Disasters
    After repeated usage, the drilling tools tend to wear and break. This leads to the following problems:
     
    The accuracy of the hole location compromised:
    When the drill bit fails to hit the preferred spot and shifts away in the same axis. The shifts in the drilled hole will give rise to tangency or breakout in annular rings.
     
    Roughness inside the drilled hole:
    Roughness leads to non-uniform plating of copper. This results in blow holes and barrel cracks. It can also result in lower insulation resistance. by penetration copper plating solution to the hole wall.
     
    Resin smear:
    The resin in the board melts due to the heat generated during the drilling. This resin sticks to the hole walls and called as resin smear. This again results in poor copper plating and leads to conductivity failure. between the via and the interior layers of the circuit. The resin smear removed by a chemical solution.
     
    Presence of entry and exit burrs:
    Burr is the unwanted part of copper sticking out of the hole after the drilling process. They seen both on the top surface of highest stacked of printed circuit board. and on the bottom surface of lowest-stacked of the printed circuit board.
     
    Nailhead:
    Exposed copper of inner layers on through holes. formed the shape of nail heading during drilling. Such a huge burden to hole brings non-uniform surface of. through holes and may cause conductivity failure of plating.
     
    Delamination:
    The partial separation of the PCB layers.
     
    All these irregularities ruin the integrity of a PCB. These problems have been a nightmare for the PCB manufacturers. For these reasons our in-house PCB engineers define PCB as, “Problems Come Back!”
     
    To drop these flaws. scholars have researched on drilling process and PCB design structure. and have come up with the following solutions:
     
    The Remedies
    Desmear process
    It is a chemical process where the melted resin that deposited on the hole walls removed. This process eliminates unwanted resin and enhances electrical conductivity through the vias.
     
    Deburr process
    It is a motorized process that. eradicates the elevated ends (crowns) of the metal (copper) called burrs. Any debris that’s left out 
     

    CNC pcb drill backing board advantage


    • Excellent flatness and thickness tolerance
    • Homogeneous high density core provides for good cleaning. and cooling of the drill bit
    • offers a smooth surface. providing good face to face contact with the PCB giving good burr control. through a wide range of drill diameters
    • Can be ‘flipped’ and used on both sides, maximizing use and material yield 

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