Xilinx Kria K26 SOM - PCB Fabrication and Assembly Requirements

The K26 SOM 3D CAD les are available for your plaorm or carrier design reference. These
les are design aides in your cooling mechanical design, system assembly interference and
clearance reviews, and board-to-board (B2B) connector placement alignment checks.
PCB Fabrication and Assembly House
Requirements
The following are requirements for the fabricaon of the PC board assembly.
• Carrier card PCB pad-to-pad tolerance should be < ±25 µm.
The blue to red cross (surface pad to surface pad) tolerance with respect to the Gerber pad
locaon should be less than ±1mil (25 µm).
• Carrier card assembly house placement capability should be < ±26 µm.
• RMS value of the PCB pad-to-pad and component placement tolerance, based on the
capabilies listed above should be < ±36 µm.
• Samtec recommends a tolerance of ±0.04 mm in the distance between the connectors.
• The combinaon of the all these requirements must be controlled to less than ±40 µm
The evaluaon of Samtec connector placement is conducted by shiing the placement of the
connector from 0% (PCB pad center aligned with connector pin center) to 15% (pin center oset
by 15% of PCB pad width). The shied connectors are capable of self-aligning aer a reow
soldering process. The following image shows that even though placement of the connector
shied by 15% of the pad width, the connector solder ball was sll able to self-align to the center
of pad.
Chapter 3: Mechanical Design Considerations
UG1091 (v1.0) April 20, 2021 www.xilinx.com
Carrier Card Design for Kria SOM 39
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