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SEMI G45-93 © SEMI 198 6, 1993 1 SEMI G45-93 RECOMMENDED PR AC TICE FOR FLASH CH A R ACTERISTICS OF THERMOSETTI NG MOLDING COM POUNDS 1 Scope This method des cribes a procedure for m easuring the flashing characteris tic…

SEMI G44-94 © SEMI 1986, 19943

purposely added to adjust a plating bath to specified

hardness are not considered as impurities.

5.4.5 Hardness — Depending on type and application,

hardness is specified, using Knoop indenter in the

following categories (testing is done as per ASTM E

384):

Type Grade

Hardness

(Knoop)

I A 90 max

B 91-129

C 130-200

II B 91-129

C 130-200

D 201 and over

III A 90 max

5.5 Reflowed Plated Tin or Plated Tin/Lead

5.5.1 Composition — As per the plated finish, Section

4.1.2 or 4.2.1, as applicable.

5.5.2 Characteristics — As per 4.1.2 and 4.2, as

applicable.

5.5.3 Thickness — The thickness of such reflowed

coatings must be a minimum of 200 microinches

measured on a significant surface.

5.5.4 Appearance — The appearance of reflowed

coatings must be smooth and continuous.

Table 1 Recommended Finishes

Undercoating

Finish Mil Spec

Over

Base

Metal

Ni Sn SnPb Au

Tin MIL-T-10727 X X

TinLead

(SnPB)

MIL-M-38510 X X

Electroplate

Solder

QQ-S-571 X X X X X

DIP(SnpB)

Gold

MIL-G-45204 X X*

*Ni undercoat required by MIL-M-38510.

6 Test Methods

Tests for the lead finishes shall be in accordance with

SEMI G35.

7 Sampling

The sampling plan, based on MIL-STD-105 shall be

agreed between vendor and customer.

NOTICE: These standards do not purport to address

safety issues, if any, associated with their use. It is the

responsibility of the user of these standards to establish

appropriate safety and health practices and determine

the applicability of regulatory limitations prior to use.

SEMI makes no warranties or representations as to the

suitability of the standards set forth herein for any

particular application. The determination of the

suitability of the standard is solely the responsibility of

the user. Users are cautioned to refer to manufacturer’s

instructions, product labels, product data sheets, and

other relevant literature respecting any materials

mentioned herein. These standards are subject to

change without notice.

The user’s attention is called to the possibility that

compliance with this standard may require use of

copyrighted material or of an invention covered by

patent rights. By publication of this standard, SEMI

takes no position respecting the validity of any patent

rights or copyrights asserted in connection with any

item mentioned in this standard. Users of this standard

are expressly advised that determination of any such

patent rights or copyrights, and the risk of infringement

of such rights, are entirely their own responsibility.

International), 3081 Zanker Road, San Jose, CA 95134. Reproduction o

the contents in whole or in part is forbidden without express written

consent of SEMI.

SEMI G45-93 © SEMI 1986, 19931

SEMI G45-93

RECOMMENDED PRACTICE FOR FLASH CHARACTERISTICS OF

THERMOSETTING MOLDING COMPOUNDS

1 Scope

This method describes a procedure for measuring the

flashing characteristics of semiconductor grade transfer

molding compounds.

2 Significance

2.1 The flashing tendency for semiconductor grade

molding compounds depends on the interaction of

several variables, including mold conditions, process

parameters, molding compound viscosity, and curing

characteristics. This test is not a valid method for

predicting the flashing performance in all mold types. It

is a method for comparing flash tendency and flashing

type of different molding compounds when evaluated

under a specific set of molding process parameters.

2.2 Flashing presents problems with subsequent

processing of plastic packaged devices after molding. A

high flashing tendency increases die wear in the trim

and form operation, may interfere with plating or solder

dip finishing operations, and may prevent good contact

for electrical test. Thus, reduced tendency toward

flashing will improve the plastic package subassembly

operations. The information from this test will be of

value in rating flash performance of any given

compound to that in production use.

3 Apparatus

3.1 Transfer molding press with a platen area

sufficient to maintain a uniform mold temperature and

having (1) a transfer piston pressure potential of 1000

psi on the material; (2) sufficient clamping pressure to

prevent flashing of the molding compound at clamping

lands; and (3) a minimum plunger speed of 25.4 mm (1

inch) per second without load. The pot diameter shall

be 31.75 to 44.45 ± 0.735 mm (1.250 to 1.750 ± 0.025

inch) and the clearance between pot and ram shall be

sufficiently small that flashing does not occur above the

first sealing groove on the ram.

3.2 Standard Flash Test Mold — Per Figure 1.

3.3 Force Gauge — With appropriate range to

calibrate transfer pressure to minimum of 10.343 mpa

(1,500 psi).

3.4 Steel Rule — Measured in 0.25 mm (0.010 in).

3.5 Halo Lamp — 3× magnification, minimum.

3.6 Thermocouple and/or Pyrometer Calibrated — In

the 160°–190°C range (calibration to be checked every

6 months).

4 Test Conditions

4.1 Molding Compounds — Refrigerated shipment

and storage of some molding compounds is necessary.

The molding compound is to be at room temperature

before the container is opened. Care must be taken to

preserve the original moisture content. The material

should be in powdered form, unless otherwise

specified.

4.2 Flash Test Mold — Shall be clean and free from

any mold release agents or lubricants. A standard mold

cleaning compound can be used to insure mold

cleanliness.

4.3 Molding Conditions

4.3.1 The temperature of the mold shall be measured

using a thermocouple inserted in the mold or with a

surface pyrometer. The ram shall be kept at the mold

temperature. Molding temperature is to be 175°C unless

otherwise specified. Temperature must be maintained

within ± 3°C (± 5°F) of the specified temperature.

4.3.2 The transfer pressure for test, as measured under

the transfer plunger, is to be 6.895 ± 0.177 mpa (1000 ±

25 psi) unless otherwise specified.

4.3.3 The weight of the charge shall be adjusted to

give a molded cull thickness of 3.303 ± 0.254 mm

(0.130 ± 0.010") excluding vertical flash.

4.3.4 The free running ram speed shall be at least 25.4

mm/sec (1"/sec). Recommended speed is 100 ± 25

mm/sec into the pot and application of pressure on the

charge shall be maintained throughout the mold cycle.

4.3.5 Unless otherwise specified, a minimum of 1.5

minutes close and cure time shall be used.

4.3.6 Flash length shall be measured in 0.25 mm

(0.010 in) intervals.

5 Procedure

5.1 Thoroughly clean the ram, pot, and mold of any

cured compound, or other foreign matter.

5.2 Heat the mold and ram to within ± 3°C of the

specified temperature.

5.3 At the beginning of each series of tests and at each

change of compound, check and set the transfer

pressure using the force gauge. The proper force gauge

setting can be determined from the formula:

ΠD

where F is the force in pounds, P is the desired pressure

on the material in psi, and D is the ram diameter in

inches.

5.4

For each material change, make at least three clean

out runs using the material to be tested before recording

data. These runs may be used to determine the charge

weight.

5.5

Weigh out the compound to the nearest 0.1 g as

previously determined to yield a cull of 3.302 ± 0.254

mm (0.130 ± 0.010 in).

5.6

Raise the ram, add the compound to the pot, and

immediately activate the transfer cycle.

5.7

Remove cull and measure thickness. If the cull is

not within 0.130 ± 0.010 in, discard the run and repeat

the test, adjusting the charge weight as necessary.

5.8

Open mold and measure longe st flash for each

channel to nearest 0.25 mm (0.010 in) using 3×

minimum magnification. Be sure to check both top and

bottom plates of mold before measuring flash.

NOTE: Care must be taken to include the measurement of

transparent and semi-transparent flash which may be present

in the smaller channel. After measurements, diligence is

required to remove all flash, including the transparent and

semi-transparent varieties prior to the next test.

5.9 Repeat Steps 5.6 through 5.8 at least 3 times for

repeatability.

6 Reporting of Results

6.1 Report the material designation and lot number.

6.2 Report the average and standard deviation of the

flash length in each channel.

6.3 Report the temperature and pressure used for the

tests.

NOTE: Common Errors/Problems:

• Inadequate preheat of flash mold and/or transfer

plunger prior to test and between shots.

• Incorrect cull thickness.

• Omission of transparent or semi-transparent flash

in measurement (often present in smallest two

channels).

• Inadequate cleaning of mold between shots.

• Starting from the end of the ruler to make flash

length measurements instead of starting at a known

distance from the end.

• Inadequate mold break-in. Three shots should be

run and disregarded before recording flash

measurements for each material.

• Sprue, channel entry point, and mating mold

surface wear may produce error in measurement

and correlation problem. The impact of wear on

results has not been determined. Extent of

permissible mold wear requires agreement between

testing organizations.