5 Most Common Causes of Plated Through-Hole (PTH) Failure
Plated through-holes connect different layers of your PCB, yet defects in PTHs can lead to electrical failures, mechanical weaknesses, and reduced board lifespan. Understanding the 5 most common causes of plated through-hole PTH failure enables you to specify designs correctly and select manufacturers preventing these costly defects before boards ship.
Cause 1: Barrel Cracks from Thermal Stress
PTH barrel cracks refer to fractures in the copper plating inside the hole, occurring at corners or along the barrel due to mechanical stress or thermal expansion. Temperature increases from 25°C to 260°C during reflow soldering cause PCB material to expand, stressing copper plating when material’s CTE is mismatched.
Thermo-mechanical stresses mainly due to mismatch in out-of-plane z-direction CTE between PTH metal and laminated material can result in PTH failure. Copper expands at 17 ppm/°C while FR-4 expands at 50-70 ppm/°C, creating differential expansion stress in the barrel.
Prevention: Choose substrate with stable thermal properties (CTE 12-15 ppm/°C), specify minimum 25μm copper plating thickness, and limit aspect ratios below 6:1.
Cause 2: Plated Voids and Incomplete Plating
Plated through-hole voids are areas where copper plating is missing or incomplete, forming during electroplating if air bubbles, contaminants, or uneven current distribution prevent uniform copper deposition. High aspect ratios (10:1) make it challenging for plating solution to reach hole centers.
Prevention: Maintain hole aspect ratios below 6:1, implement rigorous cleaning protocols, and use quality plating chemistry with proper agitation.
Cause 3: Insufficient Copper Thickness
The main issue is inconsistent plating in PTH—using too little copper leaves voids that block current flow and damage reliability. Industry standards require 20-25μm minimum, but poor control results in thinner deposits lacking mechanical strength.
Prevention: Specify minimum 25μm plating thickness, verify with microsectioning, and partner with manufacturers maintaining tight plating controls.
Cause 4: Poor Drilling Quality
Protruding glass fibers from poor drilling practices cause stress points leading to PTH failure during thermal loading. Debris blocking holes prevents reliable component mounting and soldering.
Prevention: Use sharp drill bits, implement deburring processes, and verify hole cleanliness before plating.
Cause 5: Inner Layer Connection Failures
Copper plating fails to establish proper electrical contact with internal layers when lamination or plating defects create gaps between barrel and inner copper pads.
Prevention: Maintain electroless copper thickness on plated interconnections and ensure strong grain deposit in copper structure.
Choosing Quality PTH Manufacturers
Professional manufacturers prevent PTH failures through advanced drilling equipment maintaining precision tolerances, controlled plating processes ensuring uniform thickness, rigorous quality testing including AOI and X-ray inspection, and experienced engineering providing design guidance.
Companies like MorePCB implement systematic controls preventing PTH defects. Their manufacturing capabilities include precision drilling, controlled plating, comprehensive testing, and design support. With global shipping worldwide, MorePCB ensures reliable PTH fabrication regardless of location.
FAQ
Q: What causes PTH barrel cracks?
A: Temperature increases from 25°C to 260°C during reflow soldering cause PCB material to expand, stressing copper plating when CTE is mismatched between copper (17 ppm/°C) and FR-4 (50-70 ppm/°C), creating barrel cracks.
Q: How thick should PTH copper plating be?
A: Industry standards require 20-25μm minimum copper thickness. Plating below 20μm reduces mechanical strength and increases crack susceptibility during thermal cycling.
Q: What aspect ratio is safe for PTHs?
A: Keep hole aspect ratios (board thickness to hole diameter) below 6:1. High aspect ratios like 10:1 make plating solution reach difficult, causing voids and incomplete copper deposition.
Q: How do manufacturers prevent PTH voids?
A: Quality manufacturers implement rigorous cleaning protocols removing debris, maintain proper plating chemistry with adequate agitation, control aspect ratios, and use AOI/X-ray inspection catching defects early.
Q: Can PTH failures be repaired?
A: While eyelet insertion or re-plating can repair isolated PTH damage, prevention through quality manufacturing proves far more reliable and cost-effective than repairs attempting to restore compromised connections.
