IPC-TM-650 EN 2022 试验方法.pdf - 第523页

The transmission line parameters R(f), L(f), C(f), and G(f) are a consequence of determining α (f) and β (f) from the fitted trans- mission line solution to the measurements. The final step is the extraction of the relat…

c) There must be sufficient spectral content within the TDR

step pulse for the frequency range of interest where range

of interest is determined by application.

d) The repeatability of the measurement is limited by the noise

and jitter response from the TDR instrument.

1.1.2 EBW Test Coupon and Conductor Caveats This

method is designed to be used on any conductor. However

comparison between measurements is only valid for like inter-

connect structures.

The launch vias should be designed with minimum return loss.

It is recommended that the test coupon or conductor be of a

length greater than 5.0 cm [2.0 in].

EBW applicable documents include IPC-2141, IPC-TM-650,

Method 1.9 and Method 2.5.5.7.

1.2 RIE (Method B Description) In this method a TDR

step with a specified rise time is injected into each of two

lengths of an unterminated conductor. The gated derivative of

the reflected edges is an impulse response for each respec-

tive line. The RIE value is the ratio of energy obtained by inte-

grating the impulse responses. One of the two lengths is

intended to be a relatively short piece; the other is substan-

tially longer and in close proximity to a considerably long con-

ductor on the same printed board layer. The RIE ratio is a

single value that is directly proportional to the aggregate trans-

mission line loss α, which is described in IPC-2141.

1.2.1 RIE Measurement System Limitations RIE values

can vary depending on equipment used and how the tests

were performed. Following the specified method ensures con-

sistent results. Both single-ended and differential line mea-

surements have limitations in common which include the fol-

lowing:

a) RIE values are dependent on equipment bandwidth; this

document specifies only a minimum requirement for the

TDR signal source.

b) When attempting correlation between different systems, it

is critical that all systems have the same bandwidth.

c) The probe cabling, launch, test coupon vias affect mea-

surement accuracy.

d) All RIE loss values are derived and not directly measured.

e) The RIE process utilizes a filter algorithm to improve mea-

surement consistency.

1.2.2 RIE Test Coupon and Conductor Caveats Various

limitations can be attributed to test samples and probing such

as:

a) The probe and launch structure reduces the signal energy

injected into the transmission line.

b) Crosstalk and associated effects, other than differential

coupling, are out of the scope of the RIE method.

c) The RIE method applies to reference structures and test

structures with specified transmission line lengths.

RIE applicable documents include IPC-2141, IPC-TM-650,

Methods 1.9 and 2.5.5.7.

1.3 SPP (Method C Description) The SPP method allows

the extraction of broadband printed board electrical charac-

teristics that affect signal propagation using Time Domain

Reflectometry/Time Domain Transmission (TDR/TDT) equip-

ment. The SPP method produces frequency dependent mea-

surement results. Such frequency-dependent parameters

include the propagation constant (attenuation and phase con-

stant), dielectric constant, loss tangent, and characteristic

impedance. Conductor resistivity and line capacitance are

also assessed. The extracted parameters may be used to

generate predictive causal transmission line models for sys-

tem performance evaluations as well for monitoring produc-

tion line output.

The SPP technique employs a time-domain measurement that

is used to extract the broadband permittivity. The technique is

used on representative stripline structures built with small

interface discontinuities such as lands and vias.

A short pulse is injected into two lines of different lengths.

Signal processing of the digitized pulses consists of rectangu-

lar time windowing of the unwanted reflections from interface

discontinuities. This is followed by Fourier transformation.

From the ratio of the two Fourier transforms, the total attenu-

ation α(f) and phase constant β(f) are obtained. R(f), L(f), C(f),

and G(f), namely resistance, inductance, capacitance, and

conductance per unit length, are calculated using a causally-

enforced two-dimensional (2D) field solver that has a built-in

Debye function for the relation between C(f), and G(f), which

enforces the Kramer-Kronig causality requirement. The total

attenuation α(f) and β(f) are fitted to the measured values and

smooth interpolation and extrapolation is made over the

desired frequency range. The broadband Z

(f) can also be

obtained from Equation [1-1]:

(,)=

Γ(,)

G(,)+j2πC(,)

[1-1]

IPC-TM-650

Number

2.5.5.12

Subject

Test Methods to Determine the Amount of Signal Loss on

Printed Boards

Date

07/12

Revision

Page2of24

The transmission line parameters R(f), L(f), C(f), and G(f) are a

consequence of determining α(f) and β(f) from the fitted trans-

mission line solution to the measurements. The final step is

the extraction of the relative dielectric constant ε

and loss

tangent, tanδ.

Measurements made of the capacitance and loss tangent of

an additional large parallel plate structure embedded in the

same layer with the signal conductor allows the extraction of

and tanδ at very low frequencies. The final R(f), L(f), C(f), and

G(f) are used to extract the complex permittivity using Equa-

tions [1-2] and [1-3].

(ω) =

(

C(ω)

1MHz

)

x ε

r1MHz

[1-2]

tanδ(ω) =

G(ω)

ωC(ω)

[1-3]

where C

1MHz

is the calculated line capacitance at a low

frequency such as 1 MHz and ε

r1MHz

is the value obtained at

1 MHz from the parallel plate measurement. ω is the angular

frequency and equal to 2πf.

The IPC SPP method is intended for printed boards, however

it can be extended to measure coaxial single-ended and dif-

ferential cables, flex cables, multi-chip module ceramic wiring,

single and multi-chip organic module wiring, thin-film wiring,

and on-chip wiring. The extraction results produce results in

frequency range between 10 KHz to 40 GHz, depending on

the quality of the TDR equipments and test coupon structure.

1.4 SET2DIL (Method D Description) In this method a

TDR step is injected into one half of a 101.6 mm [4.0 in] dif-

ferential pair, which has the two legs of the differential pair

shorted together at the far end. The waveforms of both halves

of the differential pair are captured and manipulated to derive

SDD21 (and Z

, if desired) of the equivalent differential pair.

1.4.1 SET2DIL Measurement System Caveats SET2DIL

produces the SDD21 value for the differential pair being mea-

sured; it is not intended to rigorously differentiate between

loss elements (conductor vs. dielectric, for instance). The

same structure can also be used to measure the differential

impedance, though that calculation isn’t covered in this speci-

fication. Some other limitations of SET2DIL include:

a) SET2DIL SDD21 measurements will include losses due to

the vias, for stripline traces. To minimize errors induced by

vias, the following limitations are made to the SET2DIL

coupon design:

i. The coupon has an effective length of 203.2 [8.0 in],

which will cause the trace losses to overwhelm small via

losses.

ii. Stripline traces on the bottom portion of the board

(lower layers) are measured from the top to minimize

via stub effects. Upper stripline layers are measured

from the bottom of the board.

b) SET2DIL SDD21 measurements will include an error term

from SDD11 effects if the differential trace being measured

isn’t 100 Ω (2x the reference impedance of 50 Ω).

i. The coupon has an effective length of 203.2 mm [8.0 in],

causing the trace insertion losses (SDD21) to overwhelm

the relatively small return loss.

ii. The primary purpose of SET2DIL is to ensure the trace

properties match that of those in simulations. Thus,

SDD21 from simulations with a 50 Ω reference can be

used as the measurement criteria for SET2DIL, making

the reference error difference moot.

1.5 FD (Method E Description) Three of the previously

described methods use TDR to determine the loss character-

istics of a printed board. This approach utilizes a Vector Net-

work Analyzer (VNA) or the fast fourier transform (FFT) of a

TDT for this purpose. The result is a direct measure of fre-

quency domain attenuation and loss. VNA equipment includes

calibration to the launch pad which must be used. The inser-

tion loss is directly related to transmission line design param-

eters utilized in signaling design analysis. The metric for the FD

method is the slope of the RMS insertion loss fit for a speci-

fied frequency range.

2 APPLICABLE DOCUMENTS

IPC-2141

Controlled Impedance Circuit Boards and High

Speed Logic Design

IPC-TM-650 Test Methods Manual

1.9 Measurement Precision Estimation for Variables Data

2.5.5.7 Characteristic Impedance of Lines on Printed Boards

by TDR

IEEE802.3ap Std 2007 Annex 69b.4.1, ‘‘Fitted attenuation’’

2.1 Technical Publications

R. Mellitz, T. Ballou, and S.G. Pytel, ‘‘Energy Based TDR Loss

Method for PB Manufacturers,’’ from IPCWorks 2005, Las

Vegas, NV.

IPC-TM-650

Number

2.5.5.12

Subject

Test Methods to Determine the Amount of Signal Loss on

Printed Boards

Date

07/12

Revision

Page3of24

B. Gore, J. Loyer, R. Mellitz, M. Gaudion, J. Burnikell, P.

Carre, ‘‘Towards a PB Production Floor Metric for Go/No Go

Testing of Lossy High Speed Transmission Lines,’’ from IPC

Expo 2008.

A. Deutsch, G. Arjavalingam, and G. Kopcsay, ‘‘Characteriza-

tion of Resistive Transmission Lines by Short Pulse Propaga-

tion,’’ in IEEE Microwave and Guided Wave Letters, vol. 2,

no.1, January 1992.

A. Deutsch, G. Arjavalingam, G. Kopcsay, and M. Deger-

strom, ‘‘Short-Pulse Propagation Technique for Characteriz-

ing Resistive Package Interconnections,’’ in IEEE Transactions

on Components, Hybrids, and Manufacturing Technology, vol.

15, no. 6, December 1992.

A. Deutsch, T. M. Winkel, G. Kopcsay, C. Surovic, B. Rubin,

G. Katopis, B. Chamberlin, R. Krabbenhoft, ‘‘Extraction of ε

(f)

and tanδ(f) for Printed Circuit Board Insulators Up to 30 GHz

Using the Short Pulse Propagation Technique’’ in IEEE Trans-

actions on Advanced Packaging, vol. 20, no. 1, February

2005.

A. Deutsch, C. W. Surovic, R. S. Krabbenhoft, G. V. Kopcsay,

B. J. Chamberlin, ‘‘Prediction of Losses Caused by Rough-

ness of Metallization in Printed-Circuit Boards,’’ IEEE Transac-

tions on Advanced Packaging, vol. 30, no.2, pp.279-287,

May 2007.

A. Deutsch, Roger Krabbenhoft, C. W. Surovic, B. Rubin,

T-M. Winkel, ‘‘Use of the SPP Technique to Account for Inho-

mogeneities in Differential Printed-Circuit-Board Wiring’’

Digest of SPI’08, Signal Propagation on Interconnects, May

12-15, Avignon, France, 2008 pp. 12-16.

G. Arjavalingam, A. Deutsch, G. V. Kopcsay, J. K. Tam,

‘‘Methods for the Measurement of the Frequency Dependent

Complex Propagation Matrix, Impedance Matrix, and Admit-

tance Matrix of Coupled Transmission Lines,’’ U.S. Patent,

patent 5,502,392, March 26, 1996.

J. Loyer, R. Kunze, ‘‘SET2DIL: Method to Derive Differential

Insertion Loss from Single-Ended TDR/TDT Measurements,’’

DesignCon 2010.

3 Test Coupons (Specimens)

3.1 Common Characteristics

The coupons for all the

methods contain transmission lines. The SPP coupon also

includes a small disc structure. The following are general

guidelines for designing transmission line test structures for

test methods within this document. These transmission line

test structures or interconnects may be placed within the

functional area of the printed board or within test coupons. A

coupon is a section of the printed board that is designated for

test structures and is removed from the panel after printed

board fabrication is completed. Differences between the char-

acteristics of test and functional interconnects may exist. The

relative merit of test structure placement relation to functional

circuit is beyond the scope of this document.

3.1.1 General Nomenclature – Coupons It is recom-

mended that coupons have labels that contain information

about the associated test line signal layer; for example, L1,

S3, etc. Labeling of the contact land for differential conductors

shall clearly indicate the matched pair.

It is recommended that test coupons include a printed board

serial number, part number, and date code.

3.1.2 Ground and Reference Planes All reference planes

in the coupon shall be connected together within the coupon

area and be independent of those planes in the functional cir-

cuit area. Ground and reference plane dispensation within the

functional area is beyond the scope of this document.

3.1.3 Differential Coupons The differential line is also

known as a balanced transmission line. The probing area

should contain four contact lands: one contact land for each

of the two signal conductors in the differential pair and two

contact lands connected to the reference plane(s).

3.1.4 Probe Launch The probe launch is comprised of a

PTH or other via structure and ground contact rectangular

pad and an example is depicted in Figure 3-1. The hole diam-

eter is recommended to be the smallest hole that is appropri-

ate for the respective technology. Some printed boards may

employ blind and buried vias. The recommended pitch

between ground and signal pad for high volume testing is

1.016 mm [0.040 in] or 2.54 mm [0.100 in]. Higher accuracy

can be achieved with smaller ground pad to signal pad spac-

ing and use of multiple ground vias.

3.1.5 Connector Launch A high bandwidth connector

launch may be used instead of probe launch as show in Fig-

ure 3-2.

Figure 3-3 provides an example of high bandwidth connector

launch.

3.1.6 General Surface Condition The panel test coupons

shall have the same surface plating and use the same solder

mask requirements as the functional printed board.

IPC-TM-650

Number

2.5.5.12

Subject

Test Methods to Determine the Amount of Signal Loss on

Printed Boards

Date

07/12

Revision

Page4of24