Skipped Deposits: Preparation, Placement and Process Control Skipped deposits are apertures that receive no paste at all, leaving a bare pad after the print. The defect is different from a deposit that is short or thin, because the failure is complete rather than partial, and the cause is usually a…

Graping Defect: 5 Causes in Solder Paste Reflow Graping is a reflow defect in which the paste on a pad turns into a cluster of small balls instead of one smooth fillet. The balls sit on the pad like a bunch of grapes, each one individually rounded, and the pad…

Pot Skimming: 6 Rules That Cut Dross and Alloy Loss Pot skimming is the removal of the oxide layer that forms on the surface of a molten solder bath, and it is the task that decides how much dross the wave carries onto the boards and how much alloy is…

Dispensing Needle: 5 Rules for Solder Paste A dispensing needle is the last few millimetres of the solder paste path, and it is where most dispensing problems start. The paste has to pass through a bore that is only a few hundred micrometres across, and the behaviour of that passage…

X-Ray Tube: Design Rules and Process Limits An X-ray tube is the source at the heart of a BGA inspection system, and it is a consumable rather than a permanent part. It emits electrons from a filament, accelerates them into a target and produces the X-rays that pass through the…

Fume Extraction on a Reflow Oven: 6 Service Checks Fume extraction on a reflow oven removes the flux vapour that the paste releases as it heats, together with the condensate that forms when that vapour cools. Without extraction the vapour condenses on the coolest surfaces inside the oven, which are…

Soldering Pallet Care: 5 Rules for Selective Solder A soldering pallet is the fixture that carries a board through a selective or wave soldering machine, and it does more than hold the board still. It masks the areas that must stay solder free, it keeps the board flat under the…

Skipped Deposits: 7 Causes in Stencil Printing Skipped deposits are apertures that receive no paste at all, leaving a bare pad after the print. The defect is different from a deposit that is short or thin, because the failure is complete rather than partial, and the cause is usually a…

SMT Line Changeover: 6 Steps That Cut Setup Time Safely Line changeover is the interval between the last good board of one product and the first good board of the next, and it is one of the largest hidden costs on an SMT line. It is not only the machine…

Emulsion Thickness: 5 Rules for Printing Screens Emulsion thickness is the depth of the light sensitive layer that sits above the mesh on a printing screen, and it is the single biggest control over how much ink is deposited. The ink fills the opening, and the volume of that opening…