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  • The consideration of the aperture size in PCB proofing
    Date :2017-4-22

    When the circuit board proofing plug-in component soldering pad, the pad size should be appropriate. The bonding pad is too large, the solder spreading area is larger, the solder joint is not full, and the surface tension of the small copper foil is too small. The gap with the aperture and the line element is too large, easy to weld, when 2~2.5 times the aperture ratio lead width 0.05~0.2mm, pad diameter, welding is the ideal conditions.


    In accordance with the requirements of the board circuit board proofing is in order to achieve the minimum diameter, the diameter is at least more than the maximum diameter of the welding terminal hole flange 0.5mm. Test pads must be provided for all nodes in accordance with ANSI/IPC 2221 requirements. A node is an electrical connection between two or more components. A test pad requires a signal name (signal node name), and printed circuit board benchmark X-Y axis and the test pad coordinate position (the test pad is located on which side of the printed circuit board).


    The aspect ratio of the plated through hole has an important influence on the ability of the circuit board manufacturers to conduct effective plating in the plated through hole. It is also important to ensure the reliability of the PTH/PTV structure. When the size of the hole is less than 1/4 of the thickness of the circuit board, the tolerance should be increased by 0.05mm. When the drilling hole diameter is 0.35mm or less, the aspect ratio is 4:1 or greater, the circuit board proofing manufacturers should use the appropriate way to cover or block the plated through hole to prevent the entry of solder. In general, the thickness of the printed circuit board and the ratio of plated through hole spacing should be less than 5: 1. The need to provide fixed device information for SMT, also printed circuit board assembly layout temperature technology, in order to "test fixtures" in circuit or often referred to as "the promotion of testability in the circuit in the nail bed fixing device with the help of.


    In order to achieve this goal:
    1 avoid plated through holes on both sides of the printed circuit board. Place the test tip through the hole to the non - element / solder surface of the printed circuit board. This approach allows the use of reliable, inexpensive devices. The number of different pore sizes should be kept at a minimum.
    2 the diameter of the test pad specially designed for detection shall not be less than 0.9mm.
    3 do not rely on the edge of the connector pointer to the pad test. Test probe is easy to damage the gold-plated pointer.
    4 test the space around the pad should be greater than 0.6mm and less than 5mm. If the height of the component is greater than 6 7mm, the test pad should be placed outside of the component 5mm.
    5 do not place any components or test pads within the edge of the printed circuit board 3mm.
    6 test pads should be placed in the center of the 2.5mm hole in a grid. If possible, allow the use of standard probes and a more reliable fixture.


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