In PCB manufacturing, solder bridging (unintended solder connection between adjacent pads) is a common issue, mainly caused by improper pad design. If left unaddressed, it can lead to short circuits and functional failure. This article introduces three pad types to prevent solder bridging.
In PCB manufacturing, solder bridging (unintended solder connection between adjacent pads) is a common issue, mainly caused by improper pad design. If left unaddressed, it can lead to short circuits and functional failure. This article introduces three pad types to prevent solder bridging.
1. Adding Tail Pads (Pullback Pads)
A tail pad is an extended trace at the edge of a pad, forming a “tail” shape. It guides molten solder along a defined path during soldering, reducing the risk of solder flowing to adjacent pads.
Design factors: length, width, and position must guide solder effectively without interfering with other components.
Application: DIP, SIP, ZIP packages.
Design Rules:
- Mandatory when pin pitch < 0.2 mm.
- For packages parallel to the PCBA flow: add tail pads on the last pin.
- For packages perpendicular to the PCBA flow: add tail pads every other pin.
2. Adding Solder Theft Pads (Solder Sucker Pads)
A solder theft pad is a small auxiliary pad placed between adjacent pads. It absorbs excess solder during soldering, preventing bridging between main pads.
Key challenge: precise control of size and position to avoid disrupting layout or function.
Application: DIP, SIP, ZIP packages.
Design Rules:
- Mandatory when pin pitch < 1.27 mm.
- Solder theft pad must be larger than the original pad.
- Must be placed outside the component outline silkscreen.
- Must share the same net as the adjacent pad or be floating (no electrical conflict).
3. Lengthening Pin Pads
Lengthening a pad increases the contact area between the pad and the pin, improving solder distribution and reducing bridging risk.
Ensure the extended portion does not interfere with other pads/components, and avoid excessive length that complicates soldering.
Application: QFP packages.
Design Rules:
- Pad width = component pin width.
- Pad length = 1 to 1.5 times the component pin length.
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