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SEMI G20-96 © SEMI 198 0, 1996 2 5 Lead Finish 5.1 Tin Electroplate 5.1.1 Composition — T he tin shall n o t be less t han 99.8% pure ti n and s hall not contain more than 0.1% carbon. The depos it is Ty pe I as defined …

SEMI G20-96 © SEMI 1980, 19961

SEMI G20-96

SPECIFICATION FOR LEAD FINISHES FOR PLASTIC PACKAGES

(ACTIVE DEVICES ONLY)

1 Purpose

This specification defines lead finishes for plastic

packages (e.g., single-in-line, dual-in-line, quad-in-line)

utilizing leadframes with SEMI specified leadframe

materials.

2 Scope

This specification defines the composition, properties,

and limits and refers to the appropriate tests for utility.

3 Referenced Documents

Unless otherwise specified, the following standards and

specifications, with appropriate issue letter at time of

order entry, form a part of this specification to the

extent, and for the purpose, specified herein.

3.1 SEMI Specifications

SEMI G4 — Specification for Integrated Circuit

Leadframe Materials Used in the Production of

Stamped Leadframes

SEMI G18 — Specification for Integrated Circuit

Leadframe Material Used in the Production of Etched

Leadframes

SEMI G55 — Test Method Measurement of Silver

Plating Brightness

SEMI G56 — Test Method Measurement of Silver

Plating Thickness

3.2 ASTM Specifications

B 487 — Measuring Metal and Oxide Coating

Thickness by Microscopical Examination of Cross

Section

B 545 — Standard Specification for Electrodeposited

Coatings of Tin

B 567 — Measurement of Coating Thickness by the

Beta Backscatter Principle

B 568 — Measurement of Coating Thickness by X-Ray

Spectrometry

E 1B 571 — Adhesion of Metallic Coatings

E 10 — Standard Test Method for Brinell Hardness for

Metallic Materials

1 American Society for Testing Materials, 100 Barr Harbor Drive,

West Conshohoken, PA 19428-2959

E 384 — Standard Test Methods for Microhardness of

Materials

3.3 Federal Specifications

QQ-S-365 — Silver Plating, Electrodeposited, General

Requirements for

QQ-S-571 — Solder, Tin Alloy: Tin Lead Alloy, and

Lead Alloy

3.4 Military Specifications

MIL-G-45204 — Gold Plating, Electrodeposited

MIL-P-81728 — Plating, Tin Lead, Electrodeposited

MIL-STD-883 — Test Methods and Procedures for

Microelectronics

MIL-T-10727 — Tin Plating; Electrodeposits or Hot-

Dipped, for Ferrous and Non-Ferrous Metals

4 Application

4.1 Table 1 lists recommended finishes for copper and

nickel/iron alloys.

4.1.1 Silver is approved as a lead finish for all alloys

but only for internal processing. When shipped to a

customer, silver must be removed and replaced by tin

lead.

4.1.2 Gold plate is usable in socketed applications as

well as in soldered applications. Hardness, grain size,

and other properties shall be specified on the

procurement drawing.

4.1.3 Solder, as used in this specification, refers to tin

lead as 63/37 or 60/40 unless otherwise specified and

agreed upon between user and supplier, and stated on

procurement drawings.

4.1.4 “Tinning” is a generic term (pr imarily used in

user industries) and means hot solder dip (near 60/40

tin lead) and not an application of tin.

4.2 Composition, limits, mechanical and physical

properties, and dimensions and tolerances for

leadframes are stated in SEMI G4 and SEMI G18.

4.3 Lead finish details are stated in Section 5.

2 Military Standards, Naval Publications and Forms Center, 5801

Tabor Ave., Philadelphia, PA 19120

SEMI G20-96 © SEMI 1980, 1996 2

5 Lead Finish

5.1 Tin Electroplate

5.1.1 Composition — The tin shall not be less than

99.8% pure tin and shall not contain more than 0.1%

carbon. The deposit is Type I as defined in MIL-T-

10727.

Table 1 Alloys

Finish Iron

Alloys

Finish Copper

Alloys

Tin MIL-T-10727

Tin (over base metal) X X

Acceptable Undercoats

1. Copper X X

2. Nickel X X

Tin Lead (Sn/Pb)

MIL-P-81728

Tin Lead (over base metal) X X

Sn/Pb

Acceptable Undercoats

1. Copper X X

2. Nickel X X

Solder Dip (Sn/Pb)

QQ-S-571

Solder Dip (over base metal) X X

Acceptable Undercoats

1. Copper X X

2. Nickel X X

3. Silver X X

Gold MIL-G-45204

Gold (over base metal) X

Acceptable Undercoats

1. Nickel X X

2. Copper Flash X

Silver QQ-S-365

Silver (over base metal) X X

Acceptable Undercoats

1. Copper X

2. Gold X

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.

5.1.3 Thickness — The plated coating as measured on

the major flat of the leads shall be a minimum of 5

micrometers (200 microinches).

5.1.4 Appearance — The surface texture of the tin

shall be non-reflective matte finish.

5.1.5 Hardness — None specified.

5.1.6 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

lead with minor impurities. Range of major constituents

shall be:

Tin 60%—95%

Lead 5%—40%

5.2.2 Purity and Application — Per MIL-P-81728.

5.2.3 Thickness — Shall be a minimum of 5

micrometers (200 microinches) measured on the major

flat of the leads.

5.2.4 The surface of the tin lead shall be non-reflective

matte finish.

5.2.5 Hardness — None specified.

5.3 Tin Lead Solder-Dip

5.3.1 Composition — 60/40 or 63/37.

5.3.2 Purity — As per Federal Specification QQ-S-

571.

5.3.3 Thickness — Shall be a minimum of 5

micrometers (200 microinches) as measured on the

major flat of the leads.

5.3.4 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

5.1 or 5.2.

2. Over the electroplated silver as per Section 5.4.

3. Over the electroplated gold as per Section 5.5.

5.3.5 Appearance — Surface shall be smooth and

continuous.

5.3.6 Hardness — None specified.

5.4 Silver Electroplate

5.4.1 Composition — Silver electroplate shall be semi-

bright, Type II as per Federal Specification QQ-S-365,

Grade B, (without supplementary tarnish resistant

treatment).

5.4.2 Thickness — Shall be a minimum of 1.25

micrometers (50 microinches) as measured on the

major flat of the leads, in accordance with SEMI G56.

5.4.3 Appearance — Smooth and continuous and

semi-bright with minimum discoloration as measured,

in accordance with SEMI G55.

5.4.4 Hardness — Hardness shall be between 90 and

135 on the Brinell Hardness Scale, in accordance with

ASTM E 10.

5.4.5 Additional Processing

5.4.5.1 Due to chemical reactions, silver electroplated

surfaces should be protected from sulfur and sulfur

bearing materials such as note paper, cardboard, and

other like materials. Sulfur-free papers shall be used for

packing.

5.4.5.2 Prior to shipment to a user, devices with silver

electroplated leads shall have the silver removed and

replaced with tin lead coated leads, unless accepted by

contract.

5.5 Gold Electroplate

5.5.1 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 Percent minimum

Type II - 99.0 Percent minimum

Type III - 99.9 Percent minimum

NOTE 1: Type II is suitable for socketing application only.

5.5.2 Thickness — Shall be a minimum of 1.25

micrometers (50 microinches) as measured on the

major flat of the leads.

5.5.3 Appearance — Appearance of surface shall be

smooth and continuous. Attributes and defects are

specified in MIL-G-45204 (workmanship paragraph).

5.5.4 Purity — Composition limits are as specified in

Section 5.5.1 above. Individual metallics in the deposit

shall not exceed 0.1%. Metallic hardening agents,

purposely added to adjust a plating bath to specified

hardness, are not considered as impurities.

5.5.5 Hardness — Depending on Type and

Application, hardness is specified, using Knoop

indenter in the following categories (testing shall be in

accordance with 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

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.