Measling that bridges uncommon conductors is unacceptable. Whitish, discrete spots or crosses below the laminate surface - usually induced by thermal shock/stress. No dedicated effort shall be expended to remove solder from unpopluated plated through holes (PTH) and/or vias. Interfacial connections (vias) in multilayer PWBs do not require the use of filler wire, and shall not be solder filled. Leads terminated straingt through the PWB shall extend a minium of 0.5 mm (0.020 in.) beyond the pad surface. Leads may be bend up to 30В° from the vertical plane to retain the part during soldering. Leads terminated straight through the PWB shall extend 0.5 mm (0.020 in.) to 2.29 mm (0.0900 in.) beyond the pad surface. Glass encased parts shall be covered with transparent/translucent resilient sleeving (or other approved material) when epoxy is used for staking, conformal coating, encapsulating or where damage from other sources is likely. Interfacial connections in double-sided PWBs require the use of filler wire if the PWB coupon is not evaluated by construction analysis. NASA-STD-8739.3, Д®xposed base metal on the vertical edge of printed wiring conductors, lands and pads is acceptable. Slight solder dewetting around the periphery of the component side termination pad shall not be cause for rejection, provided the termination exhibits flow-through and bonding of the lead/conductor to the termination pad.Д®xposed ends of leads on straight-through termination shall not be cause for rejection if the PWA is to be conformally coated.Дefects or damage (cuts, nicks, gouges, scrapes, etc.) that result in exposed base metal (except for the vertical edges of circuit traces, lands and pads) shall be rejectable. Parts having conductive cases, which are mounted over printed conductors or which are in close proximity to other conductive materials shall be separated by insulation of suitable thickness, or shall have an insulating jacket/sleeve. Clinched leads shall not violate minimum electrical spacing requirements.Д¬omponent leads shall not be clinched toward an electrically uncommon conductor. Adhesives shall not interfere with soldering, and residues shall be removed following soldering operations.ДЄdhesive material in the solder joint shall be cause for rejection.Д¬onductor/lead ends may be clinched, with the clinched length at least 1/2 the largest solder pad dimension, bent in the direction of the longest pad dimension. The termination exhibits a gap of less than two (2) insulated wire diameters (<2d) between the end of the insulation and the first point of contact of the conductor to the termination/pad.ДЄdhesives may be used to temporarily hold discrete components in position during wave or reflow soldering.

The contour of the conductor shall not be obscured at the termination end of the insulation. The insulation shall not be imbedded in the solder joint. and shall be mechanically restrained.Д¬omponents weighing in excess of 7 g (0.25 oz.) total, or 3.5 gm (0.12 oz.) per lead, shall be mechanically secured to the mounting surface by at least 4 evenly spaced bonds, when no other mechancial support is used. Parts which dissipate heat in quantities of 1 Watt or greater, or in quantities sufficient to damage the laminate shall be mounted with sufficient standoff The fillet completely wets all elements of the connection and is concave. The solder joint surfaces are smooth, nonporous and undisturbed, with a finish varying from satin to bright. The fillet completely wets all elements to the periphery of the connection and is concave. The solder joint surface is smooth, nonporous and undisturbed, with a finish varying from satin to bright.

Populated plated through holes (PTH) should exhibit a vertical solder fill of 100%, with a fully formed fillet on the solder side, and evidence of 100% wetting on the component side lead, barrel and pad. Solder fillets are smooth and shiny with concave profiles. Component leads exhibit proper bend radii and stress relief. Component and board markings are clear and legible.

While discretes are rapidly being displaced by the smaller-form surface mount technology (SMT) package, the discrete component is still widely in use, especially in extreme environmental applications where the SMT device will not perform reliability and/or is unavailable.Д¬omponents are installed per engineering documentation and are parallel to, and in contact with, the board surface. THROUGH-HOLE SOLDERING GENERAL REQUIREMENTS THROUGH-HOLE SOLDERINGДiscrete components are the backbone of the electronics world, consisting of individually packaged, leaded devices, highly integrated circuits (IC), interconnects, terminators, switches, etc.

Pcb soldering