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Unfortunately there's a multitude of different variations for pin pitches and package sizes, thermal pad geometries and so on that can make packages incompatible. For a similarly named LQFP or QFN package, for example, the pin pitch might be 0.3, 0.4, 0.5, 0.65 or 0.8 millimeters and the outline of the plastic could be, for example 7x7, 10x10 or 12x12 millimeters.
Below is an example of one of many pages of dimensions describing various LQFP variants from a single chip packager:
So there are a lot of variants. Also you must take into account the different thermal pad layout requirements for different ICs. It saves a lot of trouble to include the thermal pad layout in a package rather than expect the user to dig through datasheets to get it right.
But if you get the dimension variant correct, e.g. LFQP52 at 10x10 package, with pitch of 0.65 mm, then I guess it doesn't matter which factory makes the chip.. the pins should be all center aligned, for example.
Fine-Tuning Your Component Placement–
In addition to the general guidelines for placing components in basic order, there are other design considerations to note:
1,Direction: it is recommended to set the direction of similar components as one direction to help achieve an efficient and error free welding process.
2,Placement: Stay clear of placing components on the solder side of a board that would rest behind plated through hole components
3,Organization: To limit the number of board assembly steps, ensure that all through-hole components are placed on top of the PCB and surface mount (SMT) components are placed on the same side of the PCB.
Place power, grounding and signal wiring–
After the components are placed, it is time to handle the power, grounding and residual signal routing according to the following guidelines:
1. Position the power supply and ground plane: ensure that the power supply and ground plane are symmetrical, centered and located inside the PCB. In addition, it is recommended to keep the power and grounding wiring firm and wide.
2. Connect signal wiring: ensure that all signal wiring between all components is as short and direct as possible. If there are horizontal traces on the top of the PCB, the traces are always vertically placed on the subsequent layers of the PCB, and vice versa.
3. Define the net width: for low current signals (less than 0.3 amp), it is recommended to place a wire with a width of 0.010 inch. If the wiring should carry more current, the width should be wider. There are many trace width calculators on the Internet for different current ratings.
Keeping Things Separate–
High voltage and current spikes in the power supply circuit can seriously interfere with low voltage and current control circuits. Experienced designers deal with it in the following ways:
1. Separation: it is recommended that each power supply stage keep the power supply ground and control ground separate. If it cannot be avoided, make sure it is at the end of the supply path.
2. Placement: if the grounding layer is in the middle layer, it is recommended to place a small impedance path to minimize the risk of any power circuit interference.
3. Coupling: in order to reduce capacitive coupling due to placing a large ground plane and wiring above and below it, please try to make your analog ground only cross the analog line.
Solve the heating problem–
Many times, inexperienced PCB designers do not consider heat dissipation. However, when a PCB is subjected to a high temperature environment, it may prove to have serious design defects. Here you can deal with it:
1. Identify problematic components: it is important to analyze the data sheets of components on the PCB. Any component that is expected to generate a large amount of heat should be distributed throughout the PCB, rather than gathering them together.
2. Add heat sink: This is one of the effective ways to achieve proper heat dissipation in your PCB. For wave soldering applications on PCB with high copper content, it is also important to maintain the process temperature.
We have exemplified ten basic rules that are common in PCB design. Welcome to read and hope to help you.
According to your PCB design rules check your layout–
Multiple verification and inspection of your final design can determine the success of manufacturing. Electrical rule check (ERC) and design rule check (DRC) can help you verify the final design with established constraints. Click to view more PCB layout information.