SLVAEU0 September   2020 LM117HVQML-SP , LM117QML-SP , LM136A-2.5QML-SP , LM137JAN-SP , LM137QML-SP , LM185-1.2QML-SP , LM185-2.5QML-SP , LM2940QML-SP , LM2941QML-SP , LM4050QML-SP , LM723JAN-SP , LP2953QML-SP , TL1431-SP , TPS50601-SP , TPS50601A-SP , TPS7A4501-SP , TPS7H1101-SP , TPS7H1101A-SP , TPS7H1111-SP , TPS7H1121-SP , TPS7H2201-SP , TPS7H2211-SP , TPS7H3301-SP , TPS7H4001-SP , TPS7H4002-SP , TPS7H4011-SP , TPS7H5001-SP , TPS7H5002-SP , TPS7H5003-SP , TPS7H5004-SP , TPS7H6003-SP , TPS7H6013-SP , TPS7H6023-SP , UC1525B-SP , UC1611-SP , UC1705-SP , UC1707-SP , UC1708-SP , UC1709-SP , UC1710-SP , UC1715-SP , UC1823A-SP , UC1825-SP , UC1825A-SP , UC1825B-SP , UC1832-SP , UC1834-SP , UC1842-SP , UC1842A-SP , UC1843-SP , UC1843A-SP , UC1843B-SP , UC1844-SP , UC1844A-SP , UC1845-SP , UC1845A-SP , UC1846-SP , UC1856-SP , UC1863-SP , UC1875-SP , UC1901-SP , UC19432-SP , UCC1806-SP

 

  1.   Trademarks
  2. 1Reflow Profiles
  3. 2Critical Considerations for Gold-Plated Termination-Finishes
  4. 3Considerations for Leadless Ceramic Chip Carrier Packages
  5. 4Lead Forming
  6. 5Ceramic Packaging
  7. 6References

2 Critical Considerations for Gold-Plated Termination-Finishes

TI offers a variety of termination finishes for compliant hermetic packages, for example:

  • Alloy-42 leads with Sn63Pb37 hot solder dip.

  • Alloy-42 or Kovar leads with 50µ-in to 350 µ-in of nickel underplate and 60 µ-in to 225 µ-in of gold finish plate

  • Alloy-42 or Kovar leads with 50µ-in to 350 µ-in of nickel underplate and SN63Pb37 hot solder dip

Table 2-1 MIL-PRF-38535 TABLE A-III Composition and Coating Thickness Requirements

Coating

Minimum

Maximum

Hot solder dip (for all round leads)

60 µ-in

Not Specified

Hot solder dip (for all shapes other than round leads which have ≤ 25 mil pitch)

150 µ-in

Not Specified

Hot solder dip (for all shapes other than round leads with > 25 mil pitch)

200 µ-in

Not Specified

Tin-lead plate (as plated)

300 µ-in

Not Specified

Tin-lead plate (fused)

200 µ-in

Not Specified

Gold plate

50 µ-in

225 µ-in

Nickel plate (electroplate)

50 µ-in

350 µ-in

Nickel plate (electroless)

50 µ-in

250 µ-in

Nickel cladding

50 µ-in

350 µ-in

The electronics industry currently recognizes a threshold level of 3% gold by weight that can be dissolved into eutectic tin-lead solder above which the solder-joint may exhibit gold embrittlement.

With the specified gold thickness it is recommended that gold-plated leads be pre-tinned (solder-dipped) before board mounting to scavenge the gold from the leads. If this is not done, there is a chance of gold-embrittlement of the board-level solder-joints. A flowing solder-pot or two passes in a static solder-pot is recommended. Solder-pot solder composition should be periodically monitored for gold content.