IPC-TM-650 EN 2022 试验方法.pdf - 第584页

1 Scope The purpose of this test method is to quickly assess the adequacy of a given Anisotropically Conductive Adhesive Film (ACF) construction and bonding process for avoiding short circuits between adjacent traces of …

current preset on the Hipot test instrument, causing the

instrument to indicate a failure when in fact there was none.

The charging current of the capacitor is affected by the

change in voltage from one ramp step to another, the dielec-

tric constant of the dielectric, the thickness of the dielectric

and the area of the capacitor. High dielectric constant, very

thin dielectric thickness and large area of the capacitor plates

will all cause the charging current to increase. As a result, the

threshold current setting on the Hipot test instrument may

need to be adjusted to avoid generating a false failure condi-

tion.

6.2 Some thin and filled dielectrics will require a higher

threshold current setting, compared to unfilled materials. This

is particularly true of dielectrics containing ferroelectric com-

pounds, such as barium titanate. These materials may show

a nonlinear response between current and voltage. This is not

an issue at most operating voltages, which are normally low,

but can be an issue for the Hipot test. At high voltage levels,

these materials may trigger a false failure because they allow

more current than the threshold setting.

6.3 Materials, especially very thin and/or highly filled materi-

als, may have a leakage current per unit area that is area

dependent when tested at the specified test voltage. Thus,

results from the qualification test specimen or other small area

test structures may not reflect the actual leakage current per

unit area when the material is tested in a significantly larger

area format, such as that commonly done in conformance

testing by a material supplier.

6.4 Reference Documents

ASTM D149

‘‘Dielectric Breakdown Voltage of Solid Electri-

cal Insulating Materials at Commercial Power Frequencies’’

IPC-TM-650

Number

2.5.7.2

Subject

Dielectric Withstanding Voltage (Hipot Method) - Thin Dielectric

Layers for Printed Boards

Date

11/2009

Revision

Page3of3

Scope

The

purpose of this test method is to quickly

assess the adequacy of a given Anisotropically Conductive

Adhesive Film (ACF) construction and bonding process for

avoiding short circuits between adjacent traces of a flex circuit

being bonded to a low profile circuit substrate.

1.1

Purpose

ACF

materials are often used to interconnect

fine-pitch flexible circuitry to substrates such as flat-panel dis-

plays. A center to center pitch range of 80 µm to 200 µm is

not uncommon in circuits for flat panel display applications. It

is critical that the particle dispersion within the ACF be of suf-

ficient quality such that there is no inherent tendency for short

circuits between adjacent traces. In addition, it is important

that a bonding process is used, which doesn’t create any

undue accumulation of particles, which will lead to short cir-

cuits.

Applicable Documents

None

Test Specimens

3.1

order to perform this test, a custom-designed and

fabricated flex circuit substrate will need to be produced.

A suggested flex circuit construction of a design is shown in

Figure 1. Flex circuit materials should be selected to be repre-

sentative of what is being used in the application. The traces

alternate between anodic and cathodic polarity as shown.

Trace thickness, width, and pitch, should be selected in

accordance with the application. Total trace count should be

at least 100, and total width of the pattern should be slightly

less than the thermode length. Total length of the traces

should be sufficient to allow at least four bonds to be accom-

modated as shown in Figure 2 and Figure 3.

N is the number of circuit traces (at least 100).

I is the measured leakage current in amps after 10 seconds @

50V.

g is the gap spacing between adjacent traces on the circuit in

mm (of the order 0.04 mm to 0.1 mm).

IPC-2-5-10-1-1

Figure

1 Suggested Flex Circuit Layout for Insulation

Resistance Test

IPC-2-5-10-1-2

Figure

2 Preattachment of the ACF Strips to the Flex

Circuit

The

Institute for Interconnecting and Packaging Electronic Circuits

2215 Sanders Road • Northbrook, IL 60062

IPC-TM-650

TEST

METHODS MANUAL

Number

2.5.10.1

Subject

Insulation

Resistivity for Adhesive Interconnection

Bonds

Date

11/98

Revision

Originating Task Group

SMT Mounting Adhesives Task Group (5-24d)

Material

in this Test Methods Manual was voluntarily established by Technical Committees of the IPC. This material is advisory only

and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this

material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement.

Equipment referenced is for the convenience of the user and does not imply endorsement by the IPC.

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Apparatus

4.1

power supply capable of providing voltage in the

range of 10 V to 100 V, with an accuracy of at least ± 10%,

and capable of supplying current in the range of 0 mA to 1 mA

at those voltage levels

4.2

ammeter capable of measuring current in the range

of 0 to 1 mA, with an accuracy of ± 0.001 mA

4.3

Stopwatch

or other timing mechanism capable of

resolving ± 1 second

4.4

Hot-bar

bonds capable of producing ACF bonds

between flex circuits and flat panel displays, and outfitted with

a thermode of appropriate length and width for a given appli-

cation (Thermode width is generally in the range of 2 mm to 3

mm, and length is in the range of 25 mm to 50 mm.)

Procedure

5.1

Calculate

the insulation resistivity (pi) in Ohm-cm for

each of three samples. Each sample must meet the specifica-

tion requirement (see Figure 4).

pi =

(A)(B)(C)(D)(E)

(F)(G)(H)

=Ω−cm

where:

= voltage

B = number of bonds

C = width of bond (mm)

D = conductor thickness (mm)

E = total number of lines - 1

F = mm to µm conversion

G = current amps

H = trace to trace gap (mm)

Example A test circuit is designed with 100 total circuit

traces (50 anodic and 50 cathodic) on 100 µm pitch. The

trace thickness is 0.035 mm (1 oz Cu) and the trace to trace

gap is 0.05 mm. Suppose also that four ACF bonds are pre-

pared, with each bond being 3 mm wide. After applying a 50

VDC bias for 10 seconds, a leakage current of 0.5 mA is

measured.

pi =

(50)(4)(3)(0.035)(99)

(10)(0.0005)(0.050)

= 8.3E6 Ω−cm

IPC-2-5-10-1-3

Figure

3 Flex Circuit Containing Four ACF Bond Sites,

After Being Bonded to a Glass Slide

IPC-2-5-10-1-4

Figure

4 Schematic Diagram for Insulation Resistivity

Measurement

IPC-TM-650

Number

2.5.10.1

Subject

Insulation

Resistivity for Adhesive Interconnection Bonds

Date

11/98

Revision

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