Spread and Slump

The spread and slump for surface-mount adhesives may be measured according to IPC-SM-817, Method 4.5.5. 1 According to this method, sets of adhesive dots (minimum three per set), 0.65 cm in diameter and 0.25-mm thick, are deposited (for example, by screen or stencil printing) on each of two frosted glass microscope slides. One sample is stored 50-70 minutes at 25°C 5°C and 50% 5% relative humidity and then measured for spreading of the uncured adhesive. The second sample is cured and measured for the 

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Spread and slump Dielectric constant. Corrosion or Gel time (ASTM Modulus [ASTM Degree of cure Infrared... 

F/g. 2. 6 The relationship between initial slump, the flow table spread and the addition level of a superplasticizer. 

Spread or slump Observe three dots dispensed (0.65 mm diameter and 0.25 mm thick) cured and uncured. Measure uncured dots after 70 minutes <10% (5.6) Average of 1.8 0.2 mm dots on FR4 epoxy with solder resist. Check after 3 minutes uncured and cured. 

Sand boils up to 2 ft in diameter were observed along beach Site involved in a lateral spreading landslide. Slumping and fissuring of ground accompanied by some movement toward lake. Horizontal movement only several feet Three large flow slides occurred on the valley sides of the San Pedro River. Volumes of slide material were 40 X 10 8 X 10 and 3 X10 ydL Sliding distance was as much as 1000 ft... 

On release, vapours heavier than air tend to spread (i.e. to slump ) at low level and will aeeumulate in pits, sumps, depressions in ground, ete. This may promote a fire/explosion hazard, or a toxie hazard, or eause an oxygen-defieient atmosphere to form, depending on the ehemieal. 

The density of a vapour or gas at eonstant pressure is proportional to its relative moleeular mass and inversely proportional to temperature. Sinee most gases and vapours have relative moleeular masses greater than air (exeeptions inelude hydrogen, methane and ammonia), the vapours slump and spread or aeeumulate at low levels. The greater the vapour density, the greater the tendeney for this to oeeur. Gases or vapours whieh are less dense than air ean, however, spread at low level when eold (e.g. release of ammonia refrigerant). Table 6.1 ineludes vapour density values. 

The initial rate of spreading (often termed slumping) of a heavier-than-air vapor cloud can be significant, depending on the magnitude of the difference between the effective mean cloud/plume density and the air density. 

Testing techniques for the evaluation of physical properties and other properties of finished margarine products as well as low-fat spreads have been stated to include (4, 91) appearance, oral melting characteristics, oil exudation, slump (collapse), penetrations, spreadability, emulsion viscosity at 35°C (95°F), emulsion drop size, and electrical conductivity. 

Spread/slump test 8.6 Deposit three dots of adhesive 0.65 mm in diameter and 0.25 mm thick on two glass slides. Maintain sample 1 at 25 5 °C and 50 + 25% RH. Cure sample 1 per vendor instmction. <10% increase in dot size is acceptable... 

Heavy gas clouds tend to slump, flow down sloping ground, and spread in a radial direction because of gravity, even on flat ground. In contrast to a passive gas, the gas released may spread against the direction of the wind. Downwind from the source area, a dense gas... 

In terms of printability, tack, slump, and solder balling, there is no clear and consistent difference between the Sn-Pb and lead-free solder pastes (Ref 59-60), because these performances depend on the solder paste formulation, not directly on the solder alloy. Very clear and consistent differences have been observed, however, in wettability between the tin-lead and lead-free solder pastes. In general, the wettability of lead-free solder paste is not as good as the tin-lead solder paste. For example, lead-free solder paste exhibits very limited spreading on OSP during reflow, and exposed corners after reflow are quite common, unless overprint or round corner pads are used. The difference in wettability between OSP and ENIG surface finishes, which is already evident for the tin-lead solder, becomes even more pronounced for lead-free solders. This has been observed with a variety of solder paste and flux formulations from a number of vendors. 

In this article, landslide is used as a generic term to include all types of downslope movement of earth material, including types of movement that involve little or no true sliding. Thus, rock falls, debris flows, etc., are considered types of landslides. The classification system of Vames (1978) is used, which categorizes landslides by the type of material involved (soil or rock) and by the type of movement (falls, topples, slides, slumps, flows, or spreads). Other modifiers commonly are used to indicate velocity of movement, degree of internal disruption, state of activity, and moisture content. 

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