Impedance control and surface finish are two of the most common sources of late-stage questions. Both should be defined in the fab notes, not discovered at assembly.
Controlled impedance
| Parameter | Capability |
|---|---|
| Tolerance | ±10% standard; ±5% with coupons |
| Single-ended | 50 Ω, 75 Ω and custom targets |
| Differential | 90 Ω, 100 Ω and custom targets |
| Verification | Test coupons on the production panel |
| Stack-up | Material and dielectric thickness confirmed before fabrication |
| Report | Measured values included with the shipment on request |
Surface finishes
| Parameter | Capability |
|---|---|
| ENIG | Best general-purpose finish; flat surface for fine-pitch and BGA |
| ENEPIG | Gold wire bonding and harsh-environment assemblies |
| HASL-LF | Cost-effective for through-hole and coarse-pitch SMT |
| OSP | Flat, simple, good for fine-pitch within a short assembly window |
| Immersion silver | High-frequency and fine-pitch, with controlled storage |
| Immersion tin | Press-fit and planar surfaces; limited shelf life |
| Hard gold | Edge connectors and wear surfaces |
How we set the stack-up
For impedance-controlled designs we start from your target values, choose the laminate and prepreg, calculate trace geometry and confirm the result against the manufacturer data sheet. The proposed stack-up is sent for approval before release. Coupons are added to the panel so the measured impedance can be compared with the target.
Do not rely on a generic stack-up from a calculator. Send the target impedance, layer count and material preference — we will confirm the construction against real laminate data.
Frequently asked questions
Can you guarantee ±5% impedance?
Yes, with coupons and an approved stack-up. The tolerance must be stated on the purchase order.
Which finish is best for BGA?
ENIG or ENEPIG are the usual choices because the surface is flat and solderable. OSP is also possible with a controlled assembly window.
Do you provide impedance reports?
Yes. Measured coupon values are reported on request and can be included with the shipment documentation.