IPC-TM-650 EN 2022 试验方法.pdf - 第531页

EBW requirements agreed upon between customer and ven- dor. 4.4.5.2 RIE Risetime The rise time (10%-90%) for RIE shall be 250 ps or as agreed upon between vendor and cus- tomer with an open tip of the probe as illustrate…

measurement procedures. ESD control components can

include static dissipative mats, deionizer systems, and opera-

tor gowning.

4.4.2 Premeasurement Checks The test measurement

should be performed after the completion of the field check

process. Ensure that the plane of the signal line of a microstrip

(or embedded microstrip) structure is at least a distance equal

to six times the width of the microstrip signal line from any

material (such as the testing table) that can affect the dielec-

tric environment of the microstrip line. If the tests are being

conducted with hand probe(s), care must be taken to ensure

that the hands and/or arms of the operator do not contact any

surface of the printed board over the transmission line being

tested. Probes should be applied to the test points with suffi-

cient force to ensure proper electrical contact between the

conductor and the probe assembly. Consistent application

(that is, force, angle of placement, etc.) of the probes onto the

test points is important to ensure repeatable measurement

results. Before recording any measurement results, ensure

that the TDR waveform is stable (that is, not drifting in ampli-

tude or time) otherwise measurement error will occur. Ensure

that the temperature and humidity of the test environment are

within TDR instrument specifications and are stable.

4.4.3 Method for Evaluation of Measurement Repeat-

ability

Measurement repeatability is described in IPC-TM-

650, Method 1.9. This method also describes a process to

evaluate the reproducibility of a measurement system for mul-

tiple operators, on different days, and when using different

instruments. This evaluation process should be followed and

a precision-to-tolerance ratio acceptable to the customer

obtained.

4.4.4 TDR Requirements In general, the following

describes minimum TDR requirements. Improvement to these

requires agreement between customer and vendor.

4.4.4.1 EBW: TDR Requirements The voltage measure-

ment resolution of the TDR unit shall be at least 1% of the

step amplitude. Step aberrations should be ± 3% or less over

the zone 10 ns to 20 ps before step transition; +10%, -5% or

less for the first 300 ps following step transition; ±3% or less

over the zone 300 ps to 5 ns following step transition; ± 1%

or less over the zone 5 ns to 100 ns following step transition;

0.5% after 100 ns following step transition. The time base

accuracy shall be less than 2 ps.

4.4.4.2 RIE: TDR Requirements The voltage measure-

ment resolution of the TDR unit shall be within 1% of the step

amplitude. Step aberrations should be ± 3% or less over the

zone 10 ns to 20 ps before step transition; +10%, -5% or less

for the first 300 ps following step transition; ± 3% or less over

the zone 300 ps to 5 ns following step transition; ± 1% or less

over the zone 5 ns to 100 ns following step transition; 0.5%

after 100 ns following step transition. The time base accuracy

shall be less than ± 1% of full scaled used. The captured time

shall be at least twice the transit time and shall contain at

least 2000 samples. The time between samples shall also be

less than 25 ps.

4.4.4.3 SPP: TDR Requirements The voltage measure-

ment resolution of the TDR unit shall be at least 1% of the

step amplitude. Step aberrations should be ± 3% or less over

the zone 10 ns to 20 ps before step transition; +10%, -5% or

less for the first 300 ps following step transition; ± 3% or less

over the zone 300 ps to 5 ns following step transition; ± 1%

or less over the zone 5 ns to 100 ns following step transition;

0.5% after 100 ns following step transition. The time base

accuracy shall be less than 2 ps for delays less than 100 ns.

4.4.4.4 SET2DIL: TDR Requirements The voltage mea-

surement resolution of the TDR unit shall be at least 1% of

the step amplitude. Step aberrations should be ± 3% or less

over the zone 10 ns to 20 ps before step transition; +10%,

-5% or less for the first 300 ps following step transition; ± 3%

or less over the zone 300 ps to 5 ns following step transition;

± 1% or less over the zone 5 ns to 100 ns following step tran-

sition; 0.5% after 100 ns following step transition. The time

base accuracy shall be less than 1 ps.

4.4.5 TDR Risetime Requirement The procedure

depicted in Figure 4-5 can be used to determine the rise time

or maximum slope of the TDR measurement system through

the probe tip. This is done to ensure that there is sufficient

high frequency content within the step pulse that is to be

injected into the device under test (DUT) for the respective test

method.

Note: The SIU is a static isolation unit designed to eliminate

static damage to the TDR sampling head. It may be included

within the TDR instrumentation.

4.4.5.1 EBW Risetime The rise time (10%-90%) for EBW

shall contain sufficient spectral content as agreed upon

between vendor and customer base on the printed board

application with the open tip of the probe. For EBW, hold the

probe in air see Figure 4-5 and measure the maximum slope

of the rise time of the step response (in Megavolts/second)

and/or the risetime. This value should be compared to the

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

Page 10 of 24

EBW requirements agreed upon between customer and ven-

dor.

4.4.5.2 RIE Risetime The rise time (10%-90%) for RIE

shall be 250 ps or as agreed upon between vendor and cus-

tomer with an open tip of the probe as illustrated in Figure 4-5.

4.4.5.3 SPP Risetime The rise time (10%-90%) for SPP

shall be 11 to 35 ps or less at the open tip of the probe or

cable connector as illustrated in Figure 4-5. SPP has an addi-

tional requirement of an impulse forming network to be

located between the TDR head and the test probe.

4.4.5.4 SET2DIL Risetime The rise time (10-90%) for

SET2DIL shall be <35 ps at the open tip of the probe or cable

connector as illustrated in Figure 4-5.

4.4.6 TDR Impedance The impedance of the TDR unit

should be 50 Ω with an impedance uncertainty less than or

equal to ± 0.5 Ω.

4.4.7 TDR System Calibration Follow the TDR instrument

manufacturer’s recommendation for the frequency of factory

calibration. Since RIE is related to the ratio of loss, field cali-

bration reverts to insuring proper results from calibration stan-

dards.

4.4.8 SPP Impulse Forming Network Requirement The

pulse width at the output of the IFN observed at the probe tip

shall be a minimum of 20 ps. The recommendation is to have

a 20 ps to 60 ps pulse width detected in TDT through the

measurement set-up on typical line lengths used in the test

coupon.

4.4.9 Printed Board Connectors The TDR cable connec-

tion shall utilize a ‘‘SMA,’’ 3.50 mm, or 2.92 mm connectors

at their measurement ports. It is recommended that cable

connections be tightened with a torque wrench to follow

specifications, unless otherwise specified by the manufacturer

of the connector or cable.

Three general probing solutions may be utilized to perform the

SPP extraction: microprobe pads, SMA connectors, and

handheld probes. Surface-mounted SMAs, as shown in Fig-

ure 4-6, are recommended for SPP. They may be either

bolted or slip-fitted into the alignment holes as explained ear-

lier. The bolt-down specification for a Molex SMA style con-

nector, part number 73251-1850, is shown in Figure 4-6.

4.4.10 TDR Cabling All test cables shall meet the follow-

ing minimum specifications:

a) Coaxial with a 50 ±1 Ω characteristic impedance

b) 2.92 mm, 3.50 mm, or SMA connectors

c) Max cable insertion loss ≤2.50 dB at 65 GHz, 50 GHz,

40 GHz, or 26.5 GHz, respectively

d) Probing insertion loss ≤0.33 dB at 65 GHz, 50 GHz,

40 GHz, or 26.5 GHz, respectively

IPC-25512-4-5

Figure 4-5 Measurement of Maximum Slope of Step

Risetime at Open End of Probe

TDR Instrument

probe

SIU

Maximum

risetime

Rise time

Time

IPC-25512-4-6

Figure 4-6 Bolt Down Torque Requirement for 2

Connector Styles

Connecter Type Required Torque

SMA 5 in-lb (0.56 N-m)

3.50 mm

2.92 mm

8 in-lb (0.90 N-m)

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

Page 11 of 24

4.4.11 TDR ESD Protection TDR equipment shall pro-

vide ESD protection commensurate with the test environment.

It is recommended that samples be grounded to remove any

residual static to protect against static discharge with in the

test environments.

Static can be built up on samples prior to test and can dam-

age the sampling heads in the TDR/TDT equipment. There-

fore, it is recommended that ESD protection be used. Such

protection must be supplied internally to the TDR system.

Samples should be grounded to remove any residual static

and/or passed through some type of deionization device prior

to testing. This can be done by shorting each line to ground

with a simple connection between one end of the lines and

the instrument ground. Keeping the relative humidity in the

test area between 45% and 55% may minimize the buildup of

static. Operators are always required to have a grounding

strap around one wrist havinga1MΩ resistor in series with it.

Special waxing can be used on the lab floor to prevent body

charge build-up. Always use a grounded, conductive table

mat. Always wear a heel strap. Always ground the center con-

ductor of a test cable before making a connection to static-

sensitive equipment.

4.5 SPP Test Apparatus

4.5.1 Other SPP Equipment Requirements

An LCR

meter is required that can measure capacitance at 1 MHz.

4.5.2 SPP Software The following software is required for

implementation of the SPP technique:

a) Gamma-Z software for signal processing or equivalent

b) 2D field solver such as CZ2D, which can be downloaded

from: www.alphaworks.ibm.com/tech/gammazandcz2d,

or equivalent

4.6 FD Test Apparatus The measurement equipment

needed includes a VNA, cabling, a probing solution, and a

calibration structure and calibration coefficients that are

acquired from the probe or connector manufacturer. The

probing solution should match the test sample chosen from

the above described samples. High performance connectors

and cables are recommended in performing VNA measure-

ments. Optionally, a TDT system may be used in place of a

VNA to acquire frequency domain attenuation and loss data.

5 Procedures

5.1 EBW Measurements Procedure

5.1.1 Measurement Process

This procedure will measure

the maximum slope of the rise time of the combined measure-

ment system and DUT and determine a loss factor. Recom-

mended resolution is 4000 points with a horizontal scale of

200 ps/div.

Step 1 – Probe the interconnect (see Figure 5-1) and measure

the maximum slope of the step response in Megavolts/second

(e.g., 430 Megavolts/second). The maximum slope may be

directly acquired from TDR equipment with that capability.

Step 2 – Report the Loss Factor at the test system bandwidth

(as measured within 4.4.5.1) (e.g., 430 Megavolts/second @

14.5 GHz).

5.2 RIE Measurement Procedures Figure 5-2 summa-

rizes the RIE measurement procedure.

The RIE method utilizes a comparison between a reference

loss (line) measurement and a test conductor (line) measure-

ment. The reference measurement may be a calibration stan-

dard or short length of conductor in the neighborhood and on

the same layer as the conductor to be measured.

5.2.1 TDR – Open or Unterminated Line Requirement

The RIE method requires a measurement of lines where one

end is a probe launch and the other end is left unterminated

or open. The probe injects a fast step at the launch point in

much the same manner specified in IPC-TM-650, Method

2.5.5.7. The injected step causes a wave to propagate down

the line; most of the wave is reflected by the open end of the

line and travels back to the source where it is measured as the

superposition of the incident wave and all the reflections.

IPC-25512-5-1

Figure 5-1 Measurement of Maximum Slope of Step Rise

Time at Open end of DUT

TDR Instrument

probe

SIU

Maximum

risetime

DUT

(interconnect)

Time

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

Page 12 of 24