Solder paste data plays a critical role in the PCB manufacturing process, but creating it can be complicated. There are various challenges involved, from managing data inputs to ensuring precise paste application. As a PCB manufacturer, we often need help preparing solder paste data because this process relies heavily on customer-provided data and specific assembly requirements.

However, these limitations apply only when the customer opts for fabrication services alone,as we may need more insight into the assembly process. If the customer chooses our turnkey services, where we handle fabrication and assembly, these limitations are eliminated since we manage the entire assembly process, including solder paste data preparation.

This guide outlines why these limitations exist and explains how you can better collaborate with us to ensure optimal project results.

• Paste Layer Provided: When customers include a solder paste layer, this acts as our primary reference for stencil creation.
• No Paste Layer Provided: If the paste layer is absent, we generate one using information from copper, solder mask, and drill data, but this process may not perfectly align with the customer’s soldering requirements.

• Flashed Copper Pads: We consider all flashed copper pads that are undrilled and free of solder mask as stencil openings.
• Component Lead Verification: We verify that all solderable component leads have corresponding open pads in the paste layer.
• Non-Soldered Pads: Pads without component leads but open in the stencil will get covered in molten paste. To prevent this, customers must provide a stencil file with detailed instructions for non-soldered pads.
However, for more complex decisions regarding non-soldered pads or stencil design adjustments, the customer or EMS provider, who understands the assembly needs, is responsible.

• Surface Area: The size of the paste layer openings.
• Stencil Thickness: The thickness of the stencil material.
• Aspect Ratio: This determines how much solder paste can flow through the stencil openings, impacting final solder quality.
A bare board manufacturer or PCB fabricator will need more detailed knowledge for assembly-specific data generation. Only the customer or EMS provider can determine the correct paste volume based on the type of components and PCB assembly process being used.

• Increase Paste Volume: This is done by enlarging the opening size or using a thicker stencil.
• Decrease Paste Volume: We reduce paste volume by making the stencil opening smaller or using a thinner stencil.
However, this is an EMS-specific task, as only the customer or EMS provider knows the exact requirements for their soldering process.

• Stencil thickness limitations and the effect on paste application are tied to the assembly process.
This information must come directly from EMS providers or customers since the specific assembly machinery and components must determine the stencil thickness.

• Minimum Aperture Size: If the aperture size is too small in relation to the stencil thickness, solder paste may need to be applied appropriately.
• Optimal Aperture Size: Correctly calibrated aperture sizes ensure reliable soldering results.
As a bare board manufacturer, we would not be able to assess the optimal aperture size required for the solder paste. Only the EMS provider can tailor this aspect of the data.

• Insufficient Paste: This can lead to poor solder joints, potentially resulting in faulty connections.
• Excessive Paste: Too much paste can cause solder bridges, leading to shorts between component leads.
However, the EMS provider controls these precision-based factors based on the components and assembly process.

• Lead Influence: Multiple leads of the same component may affect paste pad size and placement.
• Lead Type Impact: For components with large, flat leads, a larger paste pad may need to be split into smaller apertures to ensure proper paste application. These details are beyond the scope of what a bare board manufacturer can evaluate, making it crucial for customers or EMS providers to provide this data.

Final review and adjustment of solder paste data require a deep understanding of the PCB assembly process. Only the EMS provider can adjust the data to meet their machinery and process needs.