JLCPCB Blog

Quality & Reliability Testing

Ensuring Superior Solderability: The Critical Role of Testing in Reliable PCB Production

Key Takeaways Core Purpose: Verifies solder wetting before assembly to prevent yield drops and joint failures. Destructive Test: Per J-STD-002, tested components and coupons cannot be reused in production. Pass Standards: Requires 95 percent solder coverage on leads and 80 percent on exposed thermal pads. Key Defects: Catches non-wetting (exposed metal), dewetting (solder pulling back), and black pad on ENIG. DFM Prevention: Use thermal relief, keep silkscreen off pads, and select the right surface fi......

Aug 25, 2026

Assembly Techniques

Reflow Soldering Profile Troubleshooting: Common Defects and Fixes

In SMT manufacturing, many common reflow soldering defects - such as tombstoning, cold joints, Head-in-Pillow failures, and PCB warpage - are often caused by an improperly tuned reflow soldering profile. Small mistakes in the thermal curve can reduce solder reliability, damage components, and lower production yield. This guide shows how to diagnose and fix reflow profile problems through practical thermal adjustments. By understanding key parameters like ramp rate, soak time, peak temperature, TAL, an......

Aug 25, 2026

SMT Stencil Application & Printing

Pin-in-Paste: Through-Hole Reflow With a Stencil

Key Takeaways One Reflow Process: Pin-in-paste combines SMT and through-hole soldering into a single reflow pass, eliminating the need for separate wave, selective, or hand-soldering steps when the board has only a few through-hole components. Paste Volume Is Critical: Solder paste is roughly 50% flux by volume, so you need to print about twice the solder volume the finished joint requires. Stencil design—overprint apertures and step-up zones—makes or breaks the process. Target 75% Barrel Fill: Per IP......

Aug 25, 2026

SMT Stencil Design

Stencil Aperture Design: Geometry, Area Ratio & Tips

Key Takeaways Stencil aperture design controls paste volume, deposit shape, and print registration — it's the key controllable variable in SMT print quality. As per IPC-7525B, two math rules are non-negotiable: stencil area ratio ≥ 0.66 and stencil aspect ratio ≥ 1.5. Aperture geometry is component-dependent: 1:1 with pad for BGA, window-pane splits for QFN/BGA thermal pads, home-plate shapes for 0201/01005 chips, and modest reductions for fine-pitch QFP. Aperture reductions intentionally decrease the......

Aug 25, 2026

Stencil Selection & Ordering

DIY PCB Stencil: How to Make a Solder Paste Stencil

Key Takeaways DIY is possible: You can make a working solder paste stencil from Kapton, Mylar, or vinyl using a craft knife, vinyl cutter, or laser for larger SMD components and low-volume prototyping. 0.5 mm pitch is the practical boundary: DIY stencils work well above 0.5 mm pitch but struggle with finer QFNs, QFPs, and BGAs due to poor aperture quality and paste release. Match thickness to your smallest pad: Use 0.10–0.15 mm (4–6 mil) sheet stock, choosing thinner material for smaller pads and thic......

Aug 25, 2026

PCB Structures & Fundamentals

Optimizing Thermal Relief Pads for Better Heat Dissipation and Reliable Soldering

Key Takeaways Prevent Solder Defects: Relief spokes trap heat to stop cold joints and prevent tombstoning on small parts. Skip Power Pads: Keep thermal pads and >3A traces solid for maximum heat escape and minimal voltage drop. Match Spoke Geometry: Use thin spokes (0.10–0.20) for passives and wider spokes (0.20–0.30mm}) for standard SMD. Add Etch Margin: Size spokes 30% over fab minimums to survive over-etching during production. You have probably never changed a thermal relief pad setting in your li......

Aug 24, 2026