Alternate Multilayer Stackup

Timelines and summary

  • 2026-09-21: Initial notification of stock related delays, and EM528HR core is made available during checkout. This substrate is provided as an option during checkout and for affected customers to mitigate delays.
  • 2026-09-28 (ETA): Expected date for stock issues to be resolved, and restore FR408HR orders.
  • 2026-10-02 (ETA): Earliest date in which affected FR408HR orders may be shipping

Comparison of substrates

These are the major changes between the substrates

Value FR408HR EM528 -
Datasheet FR408-HR EM528  
Volume Resistivity 4.4*10^7 >10^10 Mohm-CM
Surface Resistivity 2.6*10^6 > 10^9 Mohm
Td(TGA) 360 420 °C
Tg (DMA) 230 250 °C
Tg (TMA)   220 °C
Tg (DSC) 190   °C
Thermal Conductivity 0.4 0.6 W/mK
Water Absorption 0.061 0.11 %
Flame Resistance UL-94 V-0 UL-94 V-0  
Substrate color white red  

The boards are visually distinguishable; The EM528 is a visible reddish color, compared to a milky white of FR408-HR. This is visible on the sides of the board, or on any exposed board surface.

The following information is not currently available, but has been requested.

  • Outgassing information
  • Dielectric Breakdown
  • Arc Resistance
  • CTI
  • RTI
  • 6 layer impedence table

If there’s additional material information not listed here or on the EM528 datasheet, but critical to your application, please contact us at [email protected] .

4 Layer EM528 Stackup

Layer Material Dk Df
1oz copper      
7.67 mil prepreg EM-528 2x3313-59% 3.76 0.005
0.5oz copper      
39.00mil core EM-528 5x7628 4.11 0.005
0.5oz copper      
7.67 mil prepreg EM-528 2x3313-59% 3.76 0.005
1oz copper      
4 layer impedance chart
Type Trace Layer Trace Width (mil) Trace Spacing (mil) Ref Layers Target (ohm) Tolerance (ohm) Predicted (ohm)
Single Ended Lyr1 14.0   0 / 2 50.0 5.0 50.4
Differential Lyr1 8.0 4.0 0 / 2 90.0 9.0 90.2
Differential Lyr1 7.0 5.0 0 / 2 100.0 10.0 100.2
Whaleshark white