EXTERNAL LEAD FINISH FOR HERMETIC PACKAGES - National Semiconductor

External Lead Finish for Hermetic Packages

For hermetic packages, National Semiconductor offers three

primary lead finishes: solder dip, gold plate and tin plate. The

component lead finish serves as a protective coating to pre-

vent oxidation of the lead base material prior to use. The

lead finish will ensure the leads are solderable for board

mount applications as well as provide long term protection

against lead corrosion. The lead finish composition and

thickness is dependent on the package type and the applica-

tions in which the package is used. Lead finish for Mil/Aero

product and all commercial product except Cerquad and se-

lected metal cans conforms to the requirements of

Mil-M-38510.

SOLDER DIP

The solder dip lead finish for hermetic packages is a

60%–63%tin, 40%–37%lead alloy. The finish is applied by

dipping the package leads or terminals into the molten sol-

der. Solder dipped leads provide excellent solderability. Sol-

der dip lead finish is typically lower in cost as compared to

gold or tin plating. The solder thickness and composition

conforms to the requirements of Mil-M-38510.

GOLD PLATE

Gold plated leads are used for many multilayer ceramic

packages and metal can packages. For multilayer ceramic

packages, pure gold is electroplated over an electrolytic

nickel underplate. The gold plating for metal can packages is

also pure electrolytically plated, but it may be applied over an

electroless or an electrolytic nickel plate.

Gold plate is used on package types that cannot be solder

dipped or as process simplification. Multilayer ceramic pack-

ages such as ceramic quad flatpacks (CQFP) and ceramic

pin grid arrays (CPGA) are gold plated. Many metal cans are

offered with gold plated leads.

TIN PLATE

A lead finish of 100%tin plate is used on fine pitch Cerquad

packages used in commercial applications. A plating thick-

ness of 200 microinches minimum is supplied.

The following table is provided as a reference to determine

which lead finish is used for each hermetic package type of-

fered at National Semiconductor.

Lead Finish for Hermetic Packages

Package Type Package Specific External External

(Code) Designator Package Lead Finish Lead Finish

Mil-Aero Commercial

Ceramic Dual-In-Line D; DA Gold Plate or Solder Dip Gold Plate or Solder Dip

Package—Sidebrazed (SB)

Leadless Chip Carrier (LCC) E; EA Solder Dip Gold Plate or Solder Dip

Ceramic Quad J-Bend (CQJB) EL Gold Plate Gold Plate

Ceramic Quad Flatpack (CQFP) EL Gold Plate Gold Plate

Ceramic Flatpack F Gold Plate Gold Plate

Ceramic Dual-In-Line Package (Cerdip) J; JA Solder Dip Solder Dip

Small Outline Integrated Circuit, Wide MC Gold Plate Gold Plate

Ceramic Pin Grid Array (CPGA) U; UA Gold Plate Gold Plate

Cerpack W; WA Solder Dip Solder Dip

Cerquad W; WA Solder Dip Solder Dip or Tin Plate

Metal Can Package (TO) H; HA TO-5/18/39 Gold Plate or Solder Dip Gold Plate or Solder Dip

H; HA TO-46/52/72 Gold Plate or Solder Dip Gold Plate or Solder Dip

K; KA TO-3 Solder Dip Solder Dip

Metal Leaded Chip Carrier AA Solder Plate (85/15)

MQuad ACC

Solder Plate (85/15)

ACE

ALE

AUL

AUA

AUW

AUY

AUZ

August 1999

External Lead Finish for Hermetic Packages

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NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT

DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL

COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:

1. Life support devices or systems are devices or

systems which, (a) are intended for surgical implant

into the body, or (b) support or sustain life, and

whose failure to perform when properly used in

accordance with instructions for use provided in the

labeling, can be reasonably expected to result in a

significant injury to the user.

2. A critical component is any component of a life

support device or system whose failure to perform

can be reasonably expected to cause the failure of

the life support device or system, or to affect its

safety or effectiveness.

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External Lead Finish for Hermetic Packages

National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.