PCB Design Principles

writer: G May 08, 2019

1. In the substrate, the DIE pad must be in the same direction as the bonding wire, and the outgoing wire needs to be in the same direction as the pad. For each DIE, a cross-shaped pad must be placed at its diagonal position. As the alignment coordinate at the time of binding, the coordinates need to be connected to the network of the attachment, generally selected (there must be a network, otherwise the cross will not appear), and in order to prevent the cross from being overwhelmed by the copper skin, it is impossible to accurately locate, generally used It is forbidden to enclose the copper plate frame. DIE's bindings should be noted that pads that are not used, ie pads that do not have a network connection, need to be removed. As shown below. 

2. The manufacturing process of the substrate is special. Each line must be made of electroplating by electroplating to form pads and traces, or wherever copper is needed. It must be noted here that even if there is no electrical connection, that is, a pad without a network, it is necessary to pull the pad out of the frame in eco mode to copper the pad, otherwise the pad will have no copper. And the plating line that pulls out the frame must have a position where the copper of the other layer marks its corrosion, where the seventh layer of copper is used for marking. In general, the copper skin is 0.15 mm above the plate frame, and the copper edge is about 0.2 mm away from the frame. 

3. In the board frame, to determine the positive and negative, it is best to place all the devices on the same side, which is marked with three XXX, as shown in the following figure.

             

4. The pad used in the substrate is larger than the general pad, there is a special package, which is the difference between CX0201, X mark and C0201. Finished as follows:

0603 pad: The window opening area of the 1.02mmX0.92mm pad: 0.9mmX0.8mm, and the distance between the two pads is 1.5mm.

0402 pad: The window opening area of the 0.62mmX0.62mm pad: 0.5mmX0.5mm, and the distance between the two pads is 1.0mm.

0201 pad: 0.42mmX0.42mm pad window opening area: 0.3mmX0.3mm, the middle of the two pads is 0.55mm.

5. DIE requirements are as follows: the binding pad (single wire) minimum size 0.2mmX0.09mm90 degrees, the minimum spacing of each pad to 2MILS, the inner row of the ground wire and power line pad width is also required to achieve 0.2 Mm. The angle of the bond pad is adjusted according to the angle of the component wire. When Substrate is done, the tie line is not too long. The minimum distance between the master DIE and the inner bond pad is 0.4mm, and the distance between FLASHDIE and the bond pad is 0.2mm. The longest tie line should not exceed 3mm. The spacing between the two rows of bonded pads should be more than 0.27 mm apart. 

6. The SMT pad and DIE bonding pad and SMT component should be kept above 0.3mm. The distance between one DIE bonding pad and another DIE should be kept above 0.2mm. The signal trace is a minimum of 2MILS with a 2MILS spacing. The main power supply line should be 6-8MILS, and try to spread the floor area as much as possible. Power and other signal lines can be placed in places where flooring is not possible to enhance the strength of the substrate. 

7. Pay attention to the vias and pads when wiring, and the gold fingers should not be too close. The same properties of the vias and gold fingers should be at least 0.12mm. The vias of different properties should be far away from the pads and gold. finger. The minimum through hole is 0.35mm, and the inner hole is 0.2mm. When laying copper, pay attention to the fact that copper and gold fingers can't be very close, some broken copper should be deleted, and no large area is allowed to be laid. The place of copper exists. 

8. Use a grid when laying copper. The ratio is 1:4, that is, COPPERPOUR is 0.1mm and COPPER is 0.4mm. The copper angle is changed to 45 degrees.

The copper skin is shown in the figure.


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