Underfill and Edge Bonding for Assemblies Why Joints Need Reinforcement A solder joint is the mechanical as well as the electrical connection, and on a large area array package it carries a load that a small ball was never designed to take alone. Thermal cycling makes the package and the…

SMT Reflow Solder Paste Flux Residue: What Is Left Behind Modern electronics depend on boards that are assembled correctly the first time. Every product – a phone, a charger, a medical instrument or an industrial controller – relies on thousands of solder joints that must conduct current for years. This…

Stencil Design for Paste Printing The Stencil Sets the Volume Paste printing is a volumetric process, and the stencil is the tool that defines the volume. For a rectangular aperture the deposit is the area of the aperture multiplied by the foil thickness, so the design of the aperture and…

Wave and Selective Soldering Where Wave Soldering Still Fits Wave soldering remains the efficient way to solder through hole components at volume. A board passes over a standing wave of molten solder, and every joint on the underside is made in one pass, which is far faster than touching each…

PCB Copper Trace Signal Reflection: The Echo on the Line Modern electronics depend on boards that are assembled correctly the first time. Every product – a phone, a charger, a medical instrument or an industrial controller – relies on thousands of solder joints that must conduct current for years. This…

Reflow Profile Development and Control What a Profile Is A reflow profile is the temperature of the assembly as a function of time, and the oven’s settings are only a means of producing it. The distinction matters because two boards in the same oven can see different temperatures, depending on…

X-ray Inspection of Hidden Solder Joints Why Some Joints Cannot Be Seen As packages have moved to area array terminations, the solder joint has moved out of sight. A ball grid array, a chip scale package and a land grid array all connect on the underside of the body, so…

Line Clearance and Setup Verification Changeover Is a Risk Event Changing a line from one product to another is the point where the highest number of avoidable errors enter a factory. Feeder positions are re-loaded, programs are selected, stencils are swapped and the first boards of the new product are…

PCB Dielectric Thickness Measurement: Checking the Layer Depth Electronics manufacturing has become a discipline of small details. Solder paste volumes, placement accuracy, temperature profiles and inspection limits all add up to the final result. This guide looks at PCB dielectric thickness measurement from the perspective of a PCBA factory floor,…

Solder Paste Storage, Thawing and Working Life Paste Is a Chemical Product Solder paste is a suspension of alloy powder in flux, and its behaviour depends on the chemistry as much as on the metal. The flux controls the oxides, the tack and the slump, and it changes with temperature…