IPC-TM-650 EN 2022 试验方法.pdf - 第626页

• Junction overheated due to excessive forward current 6.2 Limits to Prevent Voltage Breakdown Due to Indi- vidual Transients As integrated circuit geometries shrink, dielectric breakdown voltage ratings also diminish. O…

4.2

millivoltmeter capable of measuring true mvAC/rms

having a resolution of 0.1 mv AC. The frequency response of

the millivoltmeter shall be 20 Hz-to-20 Mhz. (MilliVac MV814A,

Hewlett-Packard HP3400B, or equivalent).

4.3

millivoltmeter capable of measuring at least 60 mv

DC and having a resolution of 1 mv DC

4.4 Ohmmeter

with a digital readout unit. It shall possess

scales that can measure resistances beyond 5 MΩ with an

accuracy of ± 100 KΩ or better (± 10% or better of the lower

limit). The ohmmeter shall have a resolution of 0.1 MΩ or

better.

4.5

Storage

oscilloscope, 100 Mhz bandwidth or faster, 1

MΩ input vertical amplifier

4.6 Oscilloscope

probe - X10 Attenuation

4.7

Constant

current Source capable of providing 10 milli-

amps DC

4.8

Resistor,

4.99 Ω, 1% precision

⁄

or greater (any com-

mercially available brand carbon or metal film)

4.9

Power

line filter, 20 ampere @ 115 VAC, 50 dB insertion

loss @ 5 Mhz/50Ω

4.10

Test

box (see 5.1)

4.11

Screen

room/shielded enclosure (optional) capable of

accommodating the entire UUT, cord, and hand piece. A fil-

tered AC power receptacle shall be available from within (see

Method 2.5.33.4).

4.12

Resistor,

1.00 KΩ, 1% (any commercially available

brand carbon or metal film)

4.13

Diodes

(two), which shall be of the lowest practicable

known forward bias devices. 1N34 diodes have been found

satisfactory for this purpose.

4.14

Receptacles (two)

4.15

Line

cord

4.16

Strain

relief

4.17 BNC

Connector

4.18

Edge

card connector w/mounting hardware

4.19

Metal

(bud) box

Procedure

All

the following test procedures should be

completed to ensure compliance with ANSI/J-STD-001:

Method 2.5.33.1 Measurement of Electrical Overstress

from Soldering Hand Tools—Ground

Measurements

Method 2.5.33.2 Measurement of Electrical Overstress

from Soldering Hand Tools—Transient

Measurements

Method 2.5.33.3 Measurement of Electrical Overstress

from Soldering Hand Tools—Current

Leakage Measurements

To construct a bench top shielded enclosure for use in lieu of

a screen room, refer to:

Method 2.5.33.4 Measurement of Electrical Overstress

from Soldering Hand Tools—Shielded

Enclosure

5.1

Test Box

Testing

has shown that for UUTs that utilize

high frequency circuits, layout and cord positioning can influ-

ence the AC current leakage reading. A compact configura-

tion such as the one shown in Figure 1 minimizes those influ-

ences (see Method 2.5.33.3).

6 Notes

6.1

Pass/Fail Limits for Transients and Steady-Sate

Voltage

EOS/ESD

papers typically discuss possible dam-

age to electronic components coming from electrostatic dis-

charge (ESD). The potentials discussed typically are 100’s and

1000’s of volts. This test method is also concerned with the

possible damage to electronic components coming from elec-

trical overstress (EOS). The EOS potentials of concern will be

1’s of volts down to millivolts. This test method strives to set

achievable EOS limits for soldering/desoldering equipment

based upon the ability to construct soldering equipment as

well as resolve small potentials from background interference.

Although any electronic component can be damaged by suf-

ficient amounts of EOS/ESD, conventional wisdom states that

semiconductors are the most susceptible. Two obvious EOS/

ESD caused failure modes in semiconductors are:

• Dielectric breakdown or reverse voltage breakdown due to

excessive potential

IPC-TM-650

Number

2.5.33

Subject

Measurement

of Electrical Overstress from Soldering Hand

Tools

Date

11/98

Revision

age2of5

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•

Junction overheated due to excessive forward current

6.2

Limits to Prevent Voltage Breakdown Due to Indi-

vidual Transients

integrated circuit geometries shrink,

dielectric breakdown voltage ratings also diminish. One semi-

conductor discussed here (battery operated integrated cir-

cuits) currently represents the lowest breakdown ratings.

S-MOS Systems’ SMC62L35 single-chip microcomputer is

designed to run from a single 1.5 volt battery. It has an abso-

lute maximum voltage (damage could result) of 2 volts.

The recommended limit for individual transients is 2 volts

peak.

6.3

Limits to Prevent Overheating Due to Steady-State

Leakage

Most

semiconductor junctions are intentionally

designed, but in integrated circuits, there are also unavoidable

intrinsic junctions. Also, there are junctions that are never sup-

posed to be operated in the forward direction (i.e., JFETs and

tuning diodes). The devices are not well character-ized by the

manufacturer regarding the maximum forward current.

Regardless of the nature of the junction, simultaneous forward

current and voltage drop results in power dissipation. If the

junction power results in a sufficient temperature increase, the

junction may be changed or destroyed. It is possible to pre-

vent forward current from flowing through a junction simply by

keeping the applied voltage below the forward junction volt-

age rating. Two semiconductors discussed here represent the

lowest forward junction voltage ratings: Schottky diodes and

germanium diodes. Motorola’s MBD201 Schottky diode and

most common germanium diodes begin to conduct at 220

millivolts. The test method apparatus represents these by

including commonly available 1N34 germanium diodes. To be

sure no junction heating can be caused by the UUT, the cur-

rent should be zero. But practically, since zero is difficult to

measure, a 1 microamp maximum tolerance can be permitted

without fear of overheating the junction. The recommended

limit for current leakage is 1 microamp (flowing through a

closed circuit, which includes parallel head-to-tail germanium

diodes).

IPC-2.5.33-1

Figure

1 Current Leakage Test Circuit Conﬁguration

AC RECEPT

ACLE

FOR VOLTMETER

AC RECEPTACLE

FOR UUT

BNC CONNECTOR

FOR VOLTMETER

TEST ELECTRODE

CARD EDGE

CONNECTOR

1K RESISTOR

METAL BOX

DIODES

GRN

BLK

WHT

IPC-TM-650

Number

2.5.33

Subject

Measurement

of Electrical Overstress from Soldering Hand

Tools

Date

11/98

Revision

age3of5

电子技术应用　　　　　　　ｗｗｗ．ＣｈｉｎａＡＥＴ．ｃｏｍ

6.4

Test Results

Complete

ALL shaded areas.

Description

of UUT (brand, model configuration, etc.):

est Procedure Pass/Fail Criteria Value Recorded Status

Ground

Measurements (2.5.33.1) ≤5 ΩΩ[ Pass [ Fail

Transient Measurements/Pass 1 (2.5.33.2) ≤2 V peak V [ Pass [ Fail

Transient Measurements/Pass 2 (2.5.33.2) ≤2 V peak V [ Pass [ Fail

Transient Measurements/Pass 3 (2.5.33.2) ≤ 2 V peak V [ Pass [ Fail

Current Leakage Measurements (2.5.33.3) ≤1.0 µ-amp DC µ-amp DC [ Pass [ Fail

Current Leakage Measurements (2.5.33.3) ≤1.0 µ-amp ACrms µ-amp ACrms [ Pass [ Fail

Description of Test Equipment and Configuration

Equipment

Function Brand Model Calibration Date

millivoltmeter true mvAC/rms

DC millivoltmeter 60 mv DC

Ohmmeter resistances beyond 5

MΩ

Storage Oscilloscope 100 Mhz bandwidth or

faster, 1 MΩ input

vertical ampliﬁer

Constant Current Source 10 milliamps DC

Equipment

Scale Used Cal / Std Meas. Baseline Meas.

millivoltmeter

DC millivoltmeter

Ohmmeter

Storage Oscilloscope

Constant Current Source

Additional Comments:

Test

Completed by:

NAME:

DATE:

COMPANY: PHONE:

IPC-TM-650

Number

2.5.33

Subject

Measurement

of Electrical Overstress from Soldering Hand

Tools

Date

11/98

Revision

age4of5

电子技术应用　　　　　　　ｗｗｗ．ＣｈｉｎａＡＥＴ．ｃｏｍ