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| Question | Answer |
|---|---|
| What is the meaning of CM? | Service providers who manage manufacturing, assembly, and testing of circuit boards |
| For the SMT component to thru-hole clearance, are those recommendations for the necessary clearance for a selective solder process? | Yes, these clearances are recommended to support the selective soldering process. They ensure the soldering nozzle can correctly access the through-hole leads without interfering with or colliding with nearby SMT components, enabling reliable soldering. |
| Do any assembly parameters change when assembling HDI boards? | Yes, several assembly parameters change for HDI boards. The process requires higher placement precision, optimized soldering profiles, and more advanced inspection techniques to handle finer features and tighter tolerances. |
| Why is the pad-to-pad clearance different from the pad-to-annular ring clearance? | Pad-to-pad clearance is the spacing between two copper features and is mainly controlled by etching limits to prevent shorts. Pad-to-annular ring clearance includes additional drill registration tolerances, since the hole can shift during drilling. This requires extra spacing to avoid breakout and ensure a reliable annular ring. Hence, pad-to-annular ring clearance is typically larger because it must account for both etching and drilling variations. |
| Do you require the MPN in the centroid file (for the PNP), or just the BOM? | The MPN is required in the BOM, not in the centroid file. The centroid (PnP) file only needs reference designators, X/Y coordinates, rotation, and side. The BOM provides the MPN and component details used for assembly. |
| How do you determine the optimum reflow profile? | The optimum reflow profile is determined based on the solder type (leaded or lead-free), component characteristics, and board properties. Factors such as board density, material types, and heat dissipation characteristics also influence the profile. Reflow ovens operate with multiple zones and use predefined, recipe-based profiles as a starting point. To fine-tune the profile, thermocouples are placed on the board to monitor actual temperatures during a trial run. The collected data is analyzed to ensure accurate heating, soaking, and cooling. Adjustments are made to achieve a reliable and optimized reflow process. |
| What is the difference in how you handle circuit designs with controlled impedances. Also, what parameters do you need to specify a controlled impedance design. | Controlled impedance design begins with accurate modeling of the PCB stack-up. The design is analyzed using impedance modeling tools to determine the appropriate trace width, spacing, dielectric thickness, and material properties required to achieve the target impedance. Once the design moves to fabrication, maintaining impedance control depends on tightly managing several critical parameters. This starts with controlling the dielectric thickness during lamination, as variations can significantly impact impedance. The trace widths and their tolerances are precisely defined and verified on the inner layers before lamination. Additional factors, such as the influence of the solder mask, are also considered as they can affect the final impedance. Overall, controlled impedance is established early in the design phase through stack-up modeling and is consistently maintained throughout the manufacturing process by controlling material properties and fabrication tolerances. |
| What brand of PNP machines do you use? | We use Europlacer pick-and-place (PnP) machines for component assembly. |
| Many manufacturer part numbers include designators for reel size (3,000 vs 10,000 piece reels, etc). How do you recommend we notate that we don’t care what reel size is used, so long as the actual part is the same? | You only need to specify a single MPN for the component in the BOM. The reel size or packaging (e.g., 3,000 vs. 10,000 pieces) does not need to be specified, as long as the part itself is the same. Based on the production quantity and component requirements, the assembler will decide whether to use full reels, partial reels, or cut tape accordingly. |
| Do you run the FA oven profile on a blank board or an assembled board? | The FA oven profile is typically run on an assembled board, not a blank one. This is because the presence of components affects heat distribution and thermal behavior. Factors like component mass and heat-sinking characteristics influence how the board heats up during reflow, so profiling with an assembled board ensures more accurate and reliable results. |
| Do you prefer working with Gerber Files or OBD++ files for born fabrication. | It’s ODB++. Especially if you need assembly, we prefer ODB++. |
| Can we add multiple MPNs for one ref designator to capture the variants? | Yes, that’s possible. |
| We have chip components like 0201. It is in imperial while converting into inches is 100 and 10 of metric. 020.254=0.508mm will be the length. 010.254=0.254 mm will be the width. Another method is: 0.02425.4=0.6096 mm will be the length. 0.01225.4=0.3048 mm will be the width. Which one is the correct dimension? Do we have a method of calculating height? |
The confusion arises because the imperial code (e.g., 0201) is only a nominal label and does not represent exact physical dimensions. In practice, you should not calculate component dimensions from these codes (whether using 0.254 mm conversion or inch-based calculations), as they do not account for manufacturing tolerances, which can vary by ±5–10% depending on the supplier. The correct approach is to refer to the component’s datasheet for the exact length, width, and height. For PCB footprint design, these values should then be aligned with IPC-7351 standards, which consider maximum component dimensions and tolerances. Similarly, there is no reliable formula to calculate height from the code, you must obtain it directly from the datasheet. |