If you have any questions, feel free to ask.
The following points are worth considering:
1. **What is the tolerance of your finished BGA pad?**
Different tolerance requirements may lead PCB manufacturers to adopt varying processes to adjust or increase the size of the BGA pad. Additionally, due to the minimum spacing (pitch) requirements of PCB manufacturers, this will affect your BGA pitch design.
If the tolerance is large and the pitch is small, the finished BGA pad may be biased toward the lower tolerance limit, which could make BGA soldering more challenging.
On the other hand, if the tolerance is tight and the spacing is also small, the PCB manufacturer may not be able to compensate for the process limitations due to insufficient spacing. This could result in a significantly reduced BGA pad size or even exceed the tolerance limits (though this might occur in some cases). Furthermore, very few PCB manufacturers would accept this type of design. Delivery times and quality consistency could also become potential issues.
2. **How much compensation is required from your manufacturer to meet your finished product tolerance requirements?**
Refer to point 1 for further details.
Here is the revised version of your text with slight rewording for clarity and flow while maintaining the original technical meaning:
**3. What spacing does your manufacturer require to ensure there is no BGA pad under the solder mask?**
This is the additional space that must be reserved, in conjunction with the requirement in item 1.
It is also one of the factors influencing your BGA pitch configuration.
**4. Is a solder mask bridge required between the BGA pads?**
This is commonly referred to as the “green oil bridge” issue by PCB manufacturers.
If so, this is the third factor that requires reserved spacing.
It is also a key factor in determining your BGA pitch settings.
**5. How much spacing does your manufacturer require to ensure there is solder mask coverage on the board?**
Refer to item 4 for details.
If the spacing is too narrow, the “green oil bridge” may fail.
Without a proper “green oil bridge,” some PCB assembly manufacturers might encounter soldering issues, such as insufficient solder paste deposition.
**6. Do you need to route signals between the BGA pads?**
If routing is required, the width of the traces, the number of traces, the spacing between the traces, and the distance between the traces and areas not covered by solder mask should all be considered when defining the BGA pitch.
These factors also include items 7, 8, and 9.
**7. If routing is required, what tolerance is acceptable for the finished traces? How much compensation does your manufacturer need to achieve the required specification?**
This is similar to the consideration in item 1.
**8. If routing is required, how much spacing does your manufacturer need to ensure complete solder mask coverage over the traces?**
This is due to tool alignment deviations in the PCB manufacturing process. When operators align the imaging tool for solder mask application, 100% alignment cannot be guaranteed. This variation is influenced by both the operator’s experience and the dimensional stability of the PCB.
**9. If there is more than one routed trace, does your manufacturer need to maintain spacing between the traces after compensation (spacing) and before the etching process?**
This is a comprehensive consideration that involves items 6, 7, and 8.
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