IPC-TM-650 EN 2022 试验方法-- - 第775页

This Page Int entionally Left Blank Number 2.6.27 Subject Thermal Stress, Convection Reflow Assembly Simula tion Date 2/2020 Revision B IPC-TM-650 Page 10 of 10

5.3 Evaluation

5.3.1 Microsection

The test specimen be microsec-

tioned when this test method is used for thermal stress prior

to structural integrity evaluation. After the test specimen has

been conditioned and reflowed in accordance with the

requirements of 5.1 and 5.2, microsection the test specimen

in accordance with IPC TM-650 Method 2.1.1. Inspect speci-

mens required for microsection (e.g., A, B, A/B, AB/R, etc.) for

compliance to the applicable performance specification

and/or AABUS requirement.

For guidelines on microsection preparation see IPC-

9241.

5.3.2 Resistance Change

Resistance change be

used to evaluate IPC-2221 Appendix A (latest revision)

D-coupons for performance-based evaluation of the samples

when specified. Microsectioning of D coupons which have

been evaluated by resistance change is not required.

5.3.2.1

Percent change in resistances of each sample’s

nets

be determined using the first cycle’s peak tempera-

ture resistance as the reference.

5.3.2.2

The maximum allowable percent change in resis-

tance after the test specimen has been conditioned and

reflowed in accordance with 5.1 and 5.2

be 5% maxi-

mum unless otherwise specified.

5.3.2.3

Cycles to failure, corresponding percent change of

the failure, and the percent change of the final cycle

documented.

5.3.3

Deviations to the stated requirements or additional

requirements defined here

be AABUS.

6 Notes

6.1

The design of the convection reflow system should be

flexible enough to facilitate the creation of the reflow profiles

depicted in Figure 5-1, Figure 5-2 and Figure 5-3 for all the

applicable test specimen designs encountered. Some issues

to consider are as follows:

• Thermal mass compensation capability (energy vs. time)

• Environmental control capability (heating and cooling)

• Reproducibility of parameters

• Preheat

• Conveyor speed (if applicable)

• Heating ramp rate

• Cool down rate

• Programming capability

• Profile memory

The IPC-TM-650 website provides a non-comprehensive list-

ing of providers of convection reflow systems suitable for

meeting the reflow profiles within this test method.

6.2

Deviations to the time and temperature specified in 5.1.1

should take into consideration maintaining the solderability of

the surface finish being utilized.

6.3 Example Drawing Notes

As this method addresses

assembly issues with printed boards, it is recommended that

the user of the printed board establish a drawing note in the

procurement documentation to provide the printed board fab-

ricators with guidance relative to the intended reflow process

of the printed board. An example of such a drawing note is

provided as follows:

A. IPC D COUPONS

BE DESIGNED IAW IPC-2221

APPENDIX A AND

INCLUDE COMPONENT (A),

VIA (B) AND ALL PROPAGATED B STRUCTURES. X OF

EACH COUPON DESIGN

BE TESTED PER

MANUFACTURING PANEL.

B. THE IPC D COUPONS

BE SUBJECTED TO 6

REFLOW SIMULATIONS IAW IPC-TM-650, METHOD

2.6.27 USING THE [230 °C, 245 °C, OR 260 °C] PRO-

FILE. ACCEPTANCE CRITERIA

BE < 5%

CHANGE IN RESISTANCE.

Number

2.6.27

Subject

Thermal Stress, Convection Reflow Assembly Simulation

Date

2/2020

Revision

IPC-TM-650

—

shall

Note:

shall

SHALL

Page

This Page Intentionally Left Blank

Number

2.6.27

Subject

Thermal Stress, Convection Reflow Assembly Simulation

Date

2/2020

Revision

IPC-TM-650

Page

1 Scope

Moisture absorption can cause delamination or

other damage in printed boards subjected to soldering heat.

This test is a process control tool to determine both the bulk

moisture content and moisture absorption rate of a printed

board. It may be used to determine whether the specimen

conforms to the monitoring level of the user’s performance

specification, to assist in process development, or for process

control. This test may not provide accurate analytical results

on all specimens, depending on the thickness of the item, the

presence of copper layers or other moisture barriers within the

structure, or the presence of any volatile compounds other

than water. The weight of the specimen is compared before

and after a bake operation. The bake is intended to remove

most of the water (> 90%) from the sample, and the bake time

and temperature specified herein are minimums. To improve

test accuracy, or to prevent heat damage, other bake param-

eters may be as agreed between user and supplier (AABUS).

2 Applicable Documents

Certification of Facilities that Inspect/Test

Printed Boards, Components and Materials

3 Test Specimens

This test may be applied to actual printed boards. If the item

is too large to be weighed easily, a representative sample or

coupon may be used. The sample may be sectioned from a

larger printed board or assembly (e.g., a scrapped item), pro-

vided that the sample represents the features and construc-

tion of the whole. The sample should be sized based on the

mass capacity and physical dimensions of the analytical bal-

ance. If a coupon is used, it must include features and con-

struction similar to the item that it represents, including similar

content and distribution of copper, and must have been sub-

jected to the identical processing environments and condi-

tions. It should be realized that the use of a representative

coupon excised from a larger printed board may result in

exposed laminate edges that will result in a slightly different

absorption rate than the actual printed board.

4 Apparatus

4.1

Circulating air oven capable of maintaining a uniform

temperature of 105 +5 °C/-0 °C (221 +9 °F/-0 °F). Nitrogen

atmosphere (inert) or vacuum is not required, but will promote

drying and improve accuracy of the test.

4.2

Analytical balance capable of determining the test

sample/coupon weight in grams to 4 places of accuracy

(X.XXXX) is required. Precautions

be taken to ensure

that the analytical balance test location is not compromised by

vibration or air drafts. If the test samples are functional printed

circuit boards with embedded active devices, ESD require-

ments appropriate to handling these circuit boards

followed. The analytical balance

be calibrated in accor-

dance with IPC-QL-653.

4.3

Tweezers, tongs or equivalent be used to handle

the test sample/coupons to prevent handling contamination.

The tweezers

be cleaned prior to each test sample/

coupon weighing session.

4.4

Gloves be used when handling the test samples/

coupons to prevent handling contamination. The gloves

contribute any contamination material on the test

samples/coupons.

5 Procedure

5.1 Initial Weighing

The weight of the test sample/coupon

be determined to the nearest 0.0001g and recorded.

5.2 Bake

The test sample/coupon be baked for 24

hours at 105 +5 °C/-0 °C (221 + 9 °F/-0 °F), unless AABUS.

The intent of this bake is to remove at least 90% of the

moisture from the sample. Printed boards that are very thick,

have solid copper planes, or that are especially saturated with

moisture (which may be bound deep within inner layers) may

require longer bake times and/or higher temperatures.

5.3 Post-Bake Weighing

An extremely rigid post bake

weighing regimen must be strictly followed to accurately

determine the test sample/coupon absorption rate. The ana-

lytical balance measurement station

be organized to

prevent any interruption of the post bake weighing process.

Procedure:

1. The test sample/coupon

be removed from the circu-

lating oven and transferred immediately (within 2 minutes)

to the analytical balance measurement location.

2. Each test sample/coupon

be placed on the analyti-

cal balance and allowed to dwell for 15 seconds, and then

3000 Lakeside Drive, Suite 309S

Bannockburn, IL 60015-1249

IPC-TM-650

TEST METHODS MANUAL

Number

2.6.28

Subject

Moisture Content and/or Moisture Absorption Rate,

(Bulk) Printed Board

Date

08/2010

Revision

Originating Task Group

Board Storage and handling Subcommittee (D-35)

Association

Connecting

Electronics

Industries

IPC-QL-653

shall

not

shall

Note:

shall

Material

this

Test

Methods

Manual

was

voluntarily

established

Technical

Committees

PC.

This

material

advisory

only

and

use

adaptation

，

entirely

voluntary.

IPC

disclaims

all

liability

any

kind

the

use,

application,

adaptation

this

material.

Users

are

also

wholly

responsible

for

protecting

themselves

against

all

claims

liabilities

for

patent

infringement.

Equipment

referenced

for

the

convenience

the

user

and

does

not

imply

endorsement

IPC.

Page