Defined Impedance Calculators

Defined Impedance Calculator Banner

There are many different Impedance calculators for PCB designers to use, some are free such as the one available to Eurocircuits customers and some you need to pay for a licence or a monthly subscription.

The aim of them all is to provide the necessary track/gap and isolation values for the layout and manufacture of your PCB.

The interfaces vary from one to another as does the way you input the parameters that are used by the calculator and this is where a user must take care.

Since the very successful launch of the Eurocircuits DEFINED IMPEDANCE pool service we have received feedback that results between our calculator and others varies.

This is something that we took very seriously and launched an investigation to establish why there was a difference.

What We Discovered

It turned out that the parameters required for one system were different to another. For example, the value H1 in our calculator is not the same as H1 in another calculator.

In the example below it is in fact the H2 in the other calculator.

Different Calculator Input Graphic

Magnified Graphic of Buildup & Parameters

In addition, the H2 value in the other system is actually equal to H1 + T in our calculator as above.

Therefore, adding the same values for H1 & H2 in the Eurocircuits calculator compared to another may very well deliver different results, as the corresponding input parameters may differ.

To verify that the Eurocircuits calculator provides the correct results we ran several tests:

  • Firstly, we used the same parameters in our calculator and the Altium calculator and as expected the results we different.
  • We then corrected the parameters used in the Altium calculator to what they require (e.g. H1+T) and the results were extremely close (Zdiff = 100.035E vs 99.146463E).

It is important to use the correct dielectric constant (εr) value for the selected material.

This value will change depending upon the selected frequency.

In the Eurocircuits calculator all the known values are automatically updated based on the selected build-up.

Another point to be aware of is how the calculator generates the results. Is it calculated using the correct formula or simply using a known ‘Rule of Thumb’ equation?

For example, a ‘Rule of Thumb’ equation for a Differential Impedance value is 2x that of the Characteristic Impedance value.

This is only a rough and non-mathematical value which may vary significantly from the real value.

It is important to check how these values are derived?

Conclusion

When using an impedance calculator, you must ensure that the actual values entered, correspond to the parameters required and are not simply copied from one calculator to the next:

  • Eurocircuits’ Impedance calculator uses real values as defined in the supplier’s data sheets.
  • Eurocircuits also calculates the correct Differential Impedance values using the correct formula and not a ‘Rule of Thumb’ method.

Finally, all calculators provide theoretical impedance values as they cannot take in to account the variables and tolerances of the manufacturing process.

This means that whilst the calculator gives you a value, the actual value measured on the PCB may well be different.

It is Eurocircuits’ experience that the measured values on the PCB are within a ±10% of our calculated values.

 

Technical Specifications of all Eurocircuits Prototype & Small Volume Services – European Origin

PCB proto

STANDARD pool

RF pool

IMS pool

eC-Default Technology Values

Poolable Options

Non-Poolable Options

Poolable Options

Non-Poolable Options

Poolable Options

Non-Poolable Options

Number of layers

2, 4

0, 1, 2, 4, 6, 8

10, 12, 14, 16

2, 4

other – ask quotation

1

Max. PCB dimensions

425mm x 425mm, max 8.75dm²

425mm x 425mm, max 8.75dm²

425mm x 425mm and >8.75dm²,

larger – ask quotation

425mm x 425mm, max 8.75dm²

425mm x 425mm and >8.75dm²,

larger , ask quotation

550mm x 425mm, max 8.75dm²

550mm x 425mm and > 8.75dm²,

larger – ask quotation

Min. PCB dimensions

20mm x 20mm

5mm x 5mm

5mm x 5mm

5mm x 5mm

Base material

FR-4, Td>=325°C, T260>=60’, T288>=5’, CTEz=<3.5%, Tg>=150°C

FR-4, Td>=325°C, T260>=60’, T288>=5’, CTEz=<3.5%, Tg>=150°C

Isola 370HR, Td>=340°C, T260>=60’, T288>=30’, CTEz=<2.8%, Tg=180°C

2L – IS680, Tg 200°C

4L – IS680 + Isola 370HR , Tg180°C

Rogers RO4000 series, Tg280°C,

other – ask quotation

MOT=130°C, Tg100°C, >=1.3W/mK, CTI=600V, >=5kV, 0.77 K/W

Base material thickness: 0, 1, 2 layer

1.55mm

1.00mm, 1.55mm, 2.40mm

0.20, 0.36, 0.50, 0.80, 1.20, 2.00, 3.20mm

0.50mm other – ask quotation ALU 1.50mm, 100µm insulation

Base material thickness: Multi Layer

1.55mm

1.55mm

0.36, 0.50, 0.80, 1.00, 1.20, 2.00, 2.40, 3.20mm

1.55mm other – ask quotation

Base copper foil: 1 Layer

35µm/1oz

70µm/2oz-105µm/3oz

other – ask quotation

35µm/1oz

Base copper foil: 2 Layer

18µm/½oz

12µm/?oz-18µm/½oz-35µm/1oz

70µm/2oz-105µm/3oz

18µm/½oz

other – ask quotation

Base copper foil: Multi Layer

(outer layer – inner layer)

18µm/½oz OL – 35µm/1oz IL

12µm/?oz OL – 18µm/½oz IL,

18µm/½oz OL – 35µm/1oz IL

eC-predefined build ups,

any other – ask quotation

18µm/½oz OL – 18µm/½oz IL

other – ask quotation

Multilayer-build

eC-standard

eC-standard

eC-type 1-7, for specials “ask quotation”

eC-type 8

for specials “ask quotation”

Extra PTH cycles: blind – buried

build up to be checked by us

build up to be checked by us

Extra press cycles: sequential build up

build up to be checked by us

build up to be checked by us

Min. track width outer layer

0.150mm

0.100mm (max.18µm base Cu)

0.090mm (max.18µm base Cu)

0.100mm

0.090mm (max.18µm base Cu)

0.150mm

Min. spacing outer layer

0.150mm

0.100mm (max.12µm base Cu)

0.090mm (max.12µm base Cu)

0.125mm

0.090mm (max.12µm base Cu)

0.150mm

Min. annular ring outer layer

0.125mm

0.100mm

0.100mm

0.100mm

0.100mm

0.125mm

Min. track width inner layer

0.150mm

0.100mm (max.18µm base Cu)

0.090mm (max.18µm base Cu)

0.100mm

0.090mm (max.18µm base Cu)

Min. spacing inner layer

0.150mm

0.100mm (max.18µm base Cu)

0.090mm (max.12µm base Cu)

0.100mm

0.090mm (max.12µm base Cu)

Min. annular ring inner layer

0.125mm

0.125mm

0.125mm

0.125mm

0.125mm

Min. finished hole size

0.25mm

0.15mm

0.10mm, press fit holes

0.15mm

0.10mm, press fit holes

0.60mm

Min. outer layer pad diameter =

selected finished hole size + “value”

0.350mm (PTH)

0.250mm (NPTH)

0.300mm (PTH)

0.200mm (NPTH)

0.300mm (PTH)

0.200mm (NPTH)

0.300mm (PTH)

0.200mm (NPTH)

0.300mm (PTH)

0.200mm (NPTH)

0.250mm (NPTH)

Min. inner layer pad diameter =

selected finished hole size + “value”

0.350mm (PTH)

0.250mm (NPTH)

0.350mm (PTH)

0.250mm (NPTH)

0.350mm (PTH)

0.250mm (NPTH)

0.350mm (PTH)

0.250mm (NPTH)

0.350mm (PTH)

0.250mm (NPTH)

Min. Cu to board-edge – outer layers

0.250mm (routed)

0.250mm (routed), 0.450mm (V-cut)

0.250mm (routed), 0.450mm (V-cut)

0.250mm (routed), 0.450mm (V-cut)

Min. Cu to board-edge – inner layers

0.400mm (routed)

0.400mm (routed), 0.450mm (V-cut)

0.400mm (routed), 0.450mm (V-cut)

Extra features in copper

copper up to board edge, plated holes on the board edge, round edge plating

copper up to board edge, plated holes on the board edge, round edge plating

copper up to the board edge

Surface finish

lead-free finish at our discretion

for best price

lead-free for best price,

ENIG selective, LF HAL

ENIG overall, Im Ag, HAL Pb/Sn

ENIG selective

LF HAL, ENIG overall, Im Ag, HAL Pb/Sn

LF HAL

Soldermask type/colour

Liquid Photo Image able – green

LPI: green, black

LPI: blue, red, white, clear

LPI: green

LPI: blue, red, white, clear

LPI: white, black (white = default)

Legend colour

white (no, one or both sides)

white (no, one or both sides)

yellow, black, white PIL

white (no, one or both sides)

yellow, black, white PIL

black, white (black = default)

Extra options

peel able mask, via filling

gold fingers, carbon pads, heat sink paste

peel able mask, via filling

gold fingers, carbon pads, heat sink paste

Slots and cut-outs

2.0mm tool

0.5mm, 1.2mm, 2.0mm tool

0.5mm, 1.2mm, 2.0mm tool

2.0mm tool

Delivery panels (customer panels)

2.0mm break-routed, V-cut

2.0mm break-routed , V-cut

2.0mm break-routed , V-cut

Max. customer panel dimensions

350mm x 250mm

425mm x 425mm and >8.75dm²,

larger – ask quotation

350mm x 250mm

425mm x 425mm and >8.75dm²,

larger – ask quotation

550mm x 425mm, max 8.75dm²

550mm x 425mm and > 8.75dm²,

larger – ask quotation

Min. customer panel dimensions

50mm x 50mm

50mm x 50mm

50mm x 50mm

eC-registration compatible panel

Max 350mmx250mm, Min 50mmx50mm

Max 350mmx250mm, Min 50mmx50mm

Max 350mmx250mm, Min 50mmx50mm

Electrical test

standard

standard, option for 1L

standard

option

UL marking

available

available

not yet available

not yet available

Stencil material

130µm stainless steel

130µm stainless steel

130µm stainless steel

130µm stainless steel

Max. stencil size

595 x 595 mm

595 x 595 mm

595 x 595 mm

595 x 595 mm

The Eurocircuits default Technology Parameters are the values listed in the “PCB proto” column (except base material), these are also used in “STANDARD pool” and “RF pool.

In “STANDARD pool” and “RF pool” pooling limits and non-pooling limits are listed for all technology values.

For Tolerance Parameter relating to our PCB Services please see our current specification

To see all the eC-predefined build-ups for multilayers, please use the build-up wizard in our PCB Calculator program.

For all services the aspect ration is 1:8.

For more please see or current Classification Table in our PCB Design Guidelines.

See also our service for small and medium volume: “BINDI pool”– Eurocircuits” Asian alternative with European assured quality.