1. Dispensing processes common pitfalls and solutions.

1.1. Drawing / trailing
1.1.1. Drawing / tailing is dispensing common defect,the causes of common: plastic nozzle inner diameter is too small, dispensing pressure is too high, the spacing of Plastic nozzle and PCB is too big, plastic patch expired or bad quality, good adhesive patch, remove from the refrigerator fails to return to room temperature, dispensing too big etc.
1.1.2. Solutions: Change the larger inner diameter of plastic nozzle; lower dispensing pressure; adjust the "stopper" high; change plastic, choose the right types of plastic viscosity; plastic patch should be removed from the refrigerator to return to room temperature (about 4h) and then put into production; adjust the dispensing volume.

1.2. Plastic nozzle clogging
1.2.1. Symptom:The glue quantity of Plastic nozzle. The usual cause: not completely wash clean pinhole; patch of plastic mixed with impurities, clogging phenomenon; immiscible glue mixed.
1.2.2. Solutions:Exchange clean needles; exchange good quality plastic patch; patch of plastic grades should not be mistaken.

1.3. Empty play
1.3.1. Phenomenon is only dispensing action, but no amount of glue.Causes: patch of plastic mixed with air bubbles; plastic nozzle clogging.
1.3.2. Solution: The syringe should be off the bubble gum treatment (especially gum own equipment); replace the plastic nozzle.

1.4. Components shift
1.4.1. phenomenon is after curing adhesive patch components shifting, serious component leads are not serious on the pad.The cause is the uneven patch of plastic glue, Two chip components such as a little a more; SMD components shift or low tack adhesive patch; PCB storage time is too long after dispensing a semi-cured glue.
1.4.2. Solutions: Check that the plastic nozzle clogging, excluding the plastic uneven; adjust the placement machine working condition; change glue; PCB storage time should not be too long after dispensing (less than 4h).

1.5. After the wave will be out piece.
1.5.1. Phenomenon is adhesive strength components not enough after curing, below the specified value, and sometimes appear out of touch tablets. Cause because is because not in place, specifically temperature is not enough, the element size is too large, large endothermic; curing light aging; glue is not enough; component / PCB contamination.
1.5.2. Solutions: Adjust the curing profile, especially to improve the curing temperature,Peak of heat curing adhesive curing temperature is usually about 150 ℃, Not reach the peak temperature can lead to off-chip.Light glue, it should be observed whether curing light is aging, whether the lamp black phenomenon; whether the number of glue and components / PCB contamination is a problem that should be considered.

1.6. After curing component pin floating / shift
1.6.1. This phenomenon of failure is cured component lead float or shift after wave soldering material will enter the next pad, and in severe short-circuit, open circuit. The main causes are uneven adhesive patch, patch glue too much or component shift when patching.
1.6.2. Solutions: Adjust the dispensing process parameters; control dispensing volume; adjust placement process parameters.