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SEMI G44-94 © SEMI 198 6, 1994 3 purposely added to adjust a plating bath to specified hardness are not considered as impurities. 5.4.5 H ardness — Depending on typ e a nd application, hardne ss i s s peci fied, using Kn…
SEMI G44-94 © SEMI 1986, 1994 2
5 Lead Finish Requirements
5.1 Tin Electroplate
5.1.1 Composition — The tin deposit shall not be less
than 99.8% pure tin and shall not contain more than
0.05% pure carbon. The deposit is Type 1 as defined in
MIL-T-10727.
5.1.2 Characteristics — The procedure used for
evaluating the tin coating and the general requirements
for the coating shall comply with ASTM B 545 or the
latest current revision, except where noted below.
5.1.2.1 Thickness — The plated coating as measured
on the major flat of the leads shall be a minimum of 300
microinches (7.5 micrometers).
5.1.2.2 Appearance — Surface appearance shall be
smooth, fine grained, adherent and free from exposed
basis metal or underplate, visible blisters, pits, nodules,
porosity, indications of burning, excessive edge buildup
and other detrimental defects.
5.1.2.3 Hardness — None specified.
5.1.2.4 Preservation — Preservation coating, if
desired and agreed upon by user and supplier, is
acceptable. (Example: Stearic acid solution in xylol as
defined in MIL-T-10727.)
5.2 Tin Lead (SnPb) Electroplate
5.2.1 Composition — Major constituents shall be tin
and lead (Pb) with minor impurities. Range of major
constituents shall be:
Tin 50%-98%
Lead (Pb) 2%-50%
Nominal 60% Tin, 40% Lead (Pb)
NOTE: Users should be advised that many plating solutions
containing lead (Pb) also contain acid fluorides. Such
solutions will attack those glass materials commonly used in
ceramic packages. Adequate process controls must be
developed and used in conjunction with this plating process to
ensure package and device integrity.
5.2.2 Purity and Application — Per MIL-M-38510.
5.2.3 Thickness — Shall be a minimum of 7.5
micrometers (300 microinches) as measured on the
major flat of the leads.
5.2.4 Appearance — Surface appearance shall be
smooth, fine-grained, adherent, and free from exposed
basis metal or underplate, visible blisters, pits, nodules,
porosity, indications of burning, excessive edge buildup
and other detrimental defects.
5.2.5 Hardness — None specified.
5.3 Tin/Lead (Pb) Solder-Dip
5.3.1 Solder Pot Composition and Purity — Sn60 or
Sn63, per QQ-S-571.
5.3.2 Thickness — Shall be a minimum of 5
micrometers (200 microinches) as measured on the
major flat of the leads.
5.3.3 Process Conformance — Solder coating is
applicable as shown in Table 1. In addition, the coating
is acceptable as follows:
1. Over the electroplated tin or tin/lead as per Section
4.1 or 4.2.
2. Over the electroplated gold as per Section 4.4.
5.3.4 Appearance — Surface shall be smooth and
continuous.
5.3.5 Hardness — None specified.
5.3.6 Coverage — Electroplated packages.
5.3.6.1 The solder dip shall extend up to and beyond
the effective seating plane for Cer-DIPs.
5.3.6.2 The solder dip shall extend within .030" from
glass seal for Cer-Packs.
5.3.7 Coverage — Non-coated packages.
5.3.7.1 When applied over the base metal, hot solder
dip shall cover the entire lead to the glass seal or point
of emergence of the lead or metallized contact through
the package wall.
5.4 Gold Electroplate
5.4.1 Composition — Gold plating shall be applied in
accordance with MIL-G-45204 in any and all of the
following grades depending on application.
Type I 99.7% minimum
Type II 99.0% minimum
Type III 99.9% minimum
NOTE: Type II is suitable for socketing application only.
5.4.2 Thickness — Shall be 1.27–5.72 micrometers
(50-225 microinches) as measured on the major flat of
the leads per MIL-M-38510.
5.4.3 Appearance — Surface appearance shall be
smooth, fine-grained, adherent and free from exposed
basis metal or underplate, visible blisters, pits, nodules,
porosity, indications of burning, excessive edge
buildup, and other detrimental defects.
5.4.4 Purity — Composition limits are as specified in
Section 4.4.1 above. Individual metallics in the deposit
shall not exceed 0.1%. Metallic hardening agents,
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.
Copyright by SEMI® (Semiconductor Equipment and Materials
International), 3081 Zanker Road, San Jose, CA 95134. Reproduction o
f
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.