Alternate Multilayer Stackup
Timelines and summary
Our apologies for the surprise; Due to a stock outage, our supplier cannot use FR408-HR, for the time being. Since order timelines are important, we’re using an alternate stackup for now.
- 2025-12-31: We’ve recieved a notification that FR408HR stock is out, and the substitution EM528 stackup is being used
- (projected) 2026-1-12: FR408HR stock should be restored and put in place on other orders.
- (projected) 2026-1-19: Delayed FR408HR orders should start shipping
What do to if this substrate is unacceptable
We know how demanding our customers are, and that equivilent is not identical.
If this substrate does not work for your application, please contact us.
- For orders that are already placed; We can provide cancellations, refunds, or simply divert your order to the Isola substrate once it’s available
- For new orders simply place the order, using the new “Require FR408-HR” option during checkout. These orders will be held until stock is available.
Our sincere apologies for the mishap here.
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
- Impedence tables for 50 ohm single ended + 90/100 ohm differential.
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 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 | 8.0 |0 / 2 |90.0 |9.0 |90.2| Differential | Lyr1 | 7.0 | 7.0 |0 / 2 |100.0 |10.0 |100.2|
6 Layer Stackup
| Layer | Material | Dk | Df |
|---|---|---|---|
| 1oz copper | |||
| 4.56 mil prepreg | EM-528 - 2x106-77% | 3.35 | 0.004 |
| 0.5oz copper | |||
| 4.00 mil core | EM-528 - 1x3313-57.5% | 3.79 | 0.005 |
| 0.5oz copper | |||
| 21mil core | EM-528 - 3x7628 | 4.11 | 0.005 |
| 0.5oz copper | |||
| 4.00 mil core | EM-528 - 1x3313-57.5% | 3.79 | 0.005 |
| 0.5oz copper | |||
| 4.56 mil prepreg | EM-528 - 2x106-77% | 3.35 | 0.004 |
| 1oz copper |
