Lead Finish Troubleshooting Guides

 

Tin plating and solder plating are two common lead finish processes used in semiconductor manufacturing. The following tables serve as quick references for troubleshooting problems related to these processes.  Table 1 is a troubleshooting guide for tin plating processes, while Table 2 is intended to help with solder plating processes.  

              

Table 1. Troubleshooting Guide for Tin Plating

Problem

Cause(s)

Remedy

Formation of Dendrites

Insufficient amount of brightener/ additives/replenishment chemicals

Add more brightener/ additives/replenishment chemicals

Insufficient amount of acid

Add more acid (usually sulfuric acid)

Formation of Nodules

Presence of solids in bath

Filter the bath

Graininess

Insufficient replenishment of additive chemicals

Add more replenishment chemicals

Insufficient amount of metal

Add stannous sulfate

Burning

High plating current

Decrease the plating current

Blistering

Inadequate or poor cleaning

Perform proper cleaning

Pitting

Insufficient replenishment of additive chemicals

Add more replenishment chemicals

Reduced Throwing Power

Insufficient replenishment of additive chemicals

Add more replenishment chemicals

Insufficient amount of acid

Add more acid (usually sulfuric acid)

Insufficient amount of metal

Add stannous sulfate

Gassing

High plating current

Decrease the plating current

High plating voltage

Decrease the plating voltage

Anode Polarization

High plating current

Decrease the plating current; add anode

Formation of Brittle Deposits

Organic contamination

Conduct carbon treatment

               

Table 2. Troubleshooting Guide for Solder Plating

Problem

Cause(s)

Remedy

Poor Solderability

Organic contamination

Perform carbon treatment

Inadequate plating thickness

Increase the plating thickness

Metallic contamination (Cu > 50 mg/l)

Subject the bath to dummy plating

Excessive additive content

Dilute the bath or perform carbon treatment

Br > 20 mg/l

Dilute the bath

Low CD Dullness

High metal content

Adjust the bath; use inert anode

High bath temperature

Cool the bath to 65 deg F

Insufficient amount of acid

Add more acid

Cl > 150 mg/l

Dilute the bath

Over-all Dullness

Insufficient amount of additives

Increase additive content

Low plating current

Increase the plating current

High bath temperature

Cool the bath to 65 deg F

I > 5 mg/l

Dilute the bath

Poor Throwing Power

Insufficient amount of additives

Increase additive content

High metal content for current used

Adjust the current; dilute the bath

Insufficient amount of acid

Add more acid

Low Cathode Efficiency

Low metal content for current used

Adjust the current; increase the metal content

Insufficient amount of acid

Add more acid

Pitting in High Current Areas

Insufficient amount of additives

Increase additive content

Low metal content for current used

Increase the metal content

Tarnishing

Improper rinsing

Perform post-rinsing

Low plating thickness

Increase plating thickness

Pre-plate contamination

Eliminate pre-plate contaminants

Anode Polarization

Presence of sludge in the bath or basket

Filter the bath; clean the anodes

Burning

Insufficient amount of additives

Increase additive content

High plating current

Decrease the plating current

Low metal content

Increase the metal content

Cloudy/Turbid Solution

Presence of stannic tin in the bath

Subject the bath to appropriate treatment

Presence of chlorides or sulfates in the bath

Filter the bath and eliminate the source of chlorides and sulfates

Roughness

Presence of stannic tin in the bath

Subject the bath to appropriate treatment

Presence of insolubles in the bath

Filter the bath

Presence of lead precipitates in the bath

Filter the bath and eliminate the source of precipitates

Foaming

High additive content

Perform carbon treatment

Sn/Pb Ratio Problems

Incorrect bath

Adjust the bath composition

Poor bath agitation

Increase bath agitation

Presence of nitrates in the bath

Dilute the bath and eliminate the source of nitrates

       

See also:   Lead FinishPb-free Manufacturing

   

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