Cost of Test

Cost of test (or cost of quality) is the total expense of testing and quality assurance across the entire manufacturing flow — including wafer probe, final test, burn-in, failure analysis, and field returns, typically 10-30% of total product cost, making test optimization critical for profitability.

What Is Cost of Test?

Definition: Total testing and quality costs from wafer to field.
Scope: Probe, final test, burn-in, FA, returns, warranty.
Typical: 10-30% of total manufacturing cost.
Impact: Major component of product cost structure.

Why Cost of Test Matters

Profitability: Significant impact on margins.
Competitiveness: Lower cost of test enables better pricing.
Investment: Test equipment is major capital expense.
Optimization: High-leverage area for cost reduction.

Components

Wafer Probe: First electrical test (20-30% of test cost).
Final Test: Comprehensive package test (40-50%).
Burn-in: Extended stress testing (20-30% for high-rel).
Failure Analysis: Root cause investigation (5-10%).
Field Returns: Warranty and replacement costs (variable).

Total Cost Calculation

def calculate_total_cost_of_test(volume, probe_cost, final_test_cost,
                                  burn_in_cost, fa_cost, return_rate,
                                  return_cost):
    # Manufacturing test costs
    mfg_test_cost = volume * (probe_cost + final_test_cost + burn_in_cost)
    
    # Failure analysis
    fa_total = fa_cost
    
    # Field return costs
    returns = volume * return_rate
    return_total = returns * return_cost
    
    total_cost = mfg_test_cost + fa_total + return_total
    cost_per_unit = total_cost / volume
    
    return {
        'total_cost': total_cost,
        'cost_per_unit': cost_per_unit,
        'mfg_test': mfg_test_cost,
        'returns': return_total
    }

Optimization Strategies

Test Time Reduction: Minimize test duration while maintaining coverage.
Adaptive Testing: Skip tests based on inline data.
Yield Improvement: Reduce retest and rework.
Escape Prevention: Invest in test to avoid expensive field failures.
Equipment Utilization: Maximize tester uptime.

Trade-offs

More Testing → Higher test cost + Lower field failures
Less Testing → Lower test cost + Higher field failures

Optimal: Minimize total cost (test + field failures)

Best Practice: Optimize total cost of quality, not just manufacturing test cost. Preventing one field failure often justifies significant test investment.

Cost of test is a strategic business metric — optimizing it requires balancing manufacturing test costs against field failure costs to minimize total cost while maintaining customer satisfaction.

Cost of Test

Take cost of test further