IPC-TM-650 EN 2022 试验方法.pdf - 第530页

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 …

Note: Equipment drift may occur as a function of time and

environment; check with equipment manufacturer for proper

calibration frequency.

4.2 EBW, RIE, and SET2DIL Apparatus EBW, RIE, and

SET2DIL utilize a TDR measurement system which shall be

composed of a step generator, high-speed sampling oscillo-

scope, and all the necessary accessories for connecting the

TDR unit to the test specimen depicted in Figure 4-3. IPC-

2141 provides a short discussion of the TDR system architec-

ture, system considerations, and the TDR measurement

process.

4.3 SPP Apparatus SPP utilizes a TDR measurement sys-

tem with the addition of one more sampling output head and

impulse forming networks placed between the TDR Sample

head and on probe. This type of setup comprises a TDT sys-

tem as shown in Figure 4-4.

Three general probing solutions may be used. These include:

microprobes, SMA connectors, and handheld probes. Each of

these methods embodies a test structure(s) in near proximity

and on the same printed board layer.

4.4 Measurement System Requirements

4.4.1 System Calibration

Follow the TDR instrument

manufacturer’s recommendation for the frequency of factory

calibration. TDR system ‘‘field’’ checks are to be performed at

regular intervals to ensure proper operation of the test sys-

tembetween the less regular factory calibrations. Field checks

are required for the following reasons:

a) TDR instrument specifications vary with temperature.

b) TDR instrument specifications vary with time (drift).

c) TDR instrument specifications vary due to minor ESD dam-

age.

d) TDR instrument factory calibration may not include auxiliary

components (e.g., cables, probes, etc.).

TDR system field checks should also be performed after a

change of any system component (such as, cable, probes,

etc.). Ensure that the TDR instrument has been operating for

at least 30 minutes prior to any field check or test measure-

ment procedure. Use proper ESD control methods to avoid

damage to the TDR instrument in all field check and test

IPC-25512-4-3

Figure 4-3 TDR Measurement Components

IPC-25512-4-4

Figure 4-4 SPP TDT/IFF Measurement Components

TDR

Low Frequency

Impedance

Analyzer

Impulse

Forming

Network

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

Page9of24

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