Pin-in-Paste Technology: Bridging Traditional Through-Hole and Modern SMT Processes

In the evolving world of PCB assembly, efficiency and reliability are always top priorities. Enter the pin-in-paste (PIP) method—also known as through-hole reflow—a process that combines the strength and durability of through-hole components with the efficiency of surface mount technology (SMT). At GCT, we've seen how PIP has transformed the assembly landscape, reducing costs and simplifying manufacturing workflows without compromising quality.

What Is Pin-in-Paste?

Pin-in-paste enables through-hole components to be soldered during the SMT reflow process. This removes the need for hand soldering or wave soldering, saving time, reducing equipment requirements, and lowering manufacturing costs. Plus, PIP is often compatible with no-clean soldering processes, streamlining post-solder cleaning.

Key Benefits

• No additional hand or wave soldering
• Fewer manufacturing steps and equipment
• Seamless integration with existing SMT lines
• Reduced production costs
• Potential use of no-clean soldering processes

Pin-in-Paste in Action: GCT's USB4105 Connector

The USB4105 connector is a great example of a component designed for pin-in-paste applications. It features surface mount solder tails and through-hole shell stakes, making it ideal for hybrid soldering techniques.

Step 1: Heat Resistance

Before proceeding, it’s crucial to confirm the component can handle reflow temperatures. For the USB4105, this information is available in the Specification Overview and Product Spec.

Step 2: Pick & Place Compatibility

The USB4105 comes in tape & reel packaging, ready for SMT feeders. Its design provides a flat surface for reliable handling by pick & place machines.

Step 3: Solder Paste Printing

• Surface Mount Solder Tails: These are straightforward, using standard stencil apertures for paste application.
• Through-Hole Shell Stakes: Here’s where the magic happens. To ensure mechanical strength, the solder paste volume needs to be calculated carefully. This involves determining the plated hole and pin volumes, and applying enough paste to fill the space - often doubling the remaining volume for optimal fill.

For thicker PCBs, paste overprinting may be necessary. This technique applies extra paste around the hole to ensure adequate solder volume during reflow, thanks to capillary action. One consideration: large ground layers can dissipate heat too quickly, which may hinder proper solder joints. Thermal relief designs can help mitigate this.

Pin-in-Paste Technology: Bridging Traditional Through-Hole and Modern SMT Processes

The USB4085 raises the complexity with both through-hole pins and shell stakes. The solder paste process varies, but the principle remains the same:

USB4085 as an example

• Confirm reflow resistance
• Ensure pick & place compatibility
• Adjust paste volume for reliable solder joints

Things to Keep in Mind

While pin-in-paste offers huge advantages, successful implementation depends on several factors:

• The type of solder paste
• Paste applicator machine precision
• Stencil design
• PCB layout
• Reflow profiles
• Operator skill and experience

As always, thorough testing is key before scaling production.
For more detailed specifications and technical guidance, please contact us.