Joint Appearance and Its Relation to Reliability A joint that looks acceptable is not necessarily a joint that will last, and the two questions are answered by different methods. Appearance is a proxy for the process, and reliability is a property of the structure. What Appearance Predicts Appearance predicts whether…

Powder Grade Choice: Type 4 or Type 5 Solder Paste Solder paste powder is graded by size, and the grade decides how the paste behaves on the smallest apertures of a board. Moving from a Type 4 to a Type 5 powder can rescue a marginal fine pitch print, but…

Assembly Area Humidity and Dew Point Control An assembly area is controlled for humidity because the paste, the components and the coating all respond to it. The measurement that matters is taken where the work happens rather than at the air handling unit, and the two can differ by more…

Board Handling Between Lines A board travels further than most people realise between the start and the end of a production line, and every transfer is an opportunity for damage. Handling defects are rarely dramatic: a chipped component, a hairline crack in a solder joint, an edge that has been…

Reflow Oven Fan and Duct Maintenance A convection reflow oven is a machine whose product is a temperature profile, and the profile depends on airflow as much as on heater power. Fans, ducts, plenums and filters determine how the heat reaches the board, and their condition drifts with flux condensation,…

Nozzle and Feeder Storage System Placement tooling is expensive, numerous and easy to lose control of. A feeder that is not stored properly gets damaged, a nozzle that is stored in the wrong tray is used on the wrong component, and a rack that has no identification becomes a place…

Fine Line Etching Process Control for Dense Circuitry Fine line etching is where a design that looked comfortable on screen becomes difficult in the tank. Removing thin copper without eating into the trace width depends on chemistry, resist quality, spray uniformity and bath control, and the tolerances tighten sharply as…

Panel Design for Maximum Material Utilization and Yield Panel design is where a board’s unit cost is largely decided, long before the first laminate is cut. How many boards fit, how much material is wasted at the edges, how easily the array can be assembled and how cleanly it can…

Cleanliness Verification Methods Cleanliness is a requirement that is easy to state and hard to verify, because there is no single test that covers every contamination risk. Flux residue, ionic material, particles, oils and moisture each behave differently and each cause different failures, so the verification method has to be…

OSP Versus Immersion Tin: Shelf Life and Solderability OSP and immersion tin both present a solderable copper surface without the thermal excursion of hot air levelling, and both are popular on fine pitch boards where a flat finish matters. They differ in what they protect, how long they last and…