SMT Procedure Specifications and Usual Anomalies

The SMT procedure requirements is the surface mount technology innovation, which is the standard need in PCB assembly procedure and an
important basis for making certain product quality.

What Are the SMT Procedure Specifications?

1) Tools Specifications

Placement machine: the model, specs, performance, and usage techniques need to meet
requirements.

SMT Reflow oven: reflow stove’s design, specs, efficiency, use techniques, etc.

Visual inspection equipment: design, specs, performance, and use methods have to meet
specs.

Automated testing equipment: models, performance, and use techniques need to adapt the
standard.

2) Material Specifications

Solder paste: solder paste model, specifications, efficiency, usage approaches, and so
on.

Parts: element model, specifications, efficiency, and usage methods must fulfill
conventional.

PCB: PCB design, specifications, performance,
use methods, etc.

3) Refine Requirements

Solder paste printing process: actions, criteria, preventative measures, etc. of solder
paste printing.

SMT procedure: SMT steps, criteria, safety measures, and so on.

Reflow procedure: reflow steps, criteria, preventative measures, etc.

4) Inspection Specs

Visual inspection: techniques, criteria, frequency, etc. of visual inspection.

Automated testing: approaches, standards, frequency, etc. of automated testing.

Common Problems of SMT

SMT procedure anomalies such as such as solder beads, tombstones, bridging, and rejection can result in
item high quality problems.

1) Solder Beads

Solder beads are one of the usual abnormalities in the SMT procedure.

It shows up as little fragments of solder showing up around the pad. The major factors for the
development of solder beads include:

• Inappropriate choice of solder paste.

• The steel plate opening is not ideal.

• The installing stress is too high.

• Improperly the heating system temperature level curve.

2)Erect a monument

It appears as a rectangle-shaped chip element with one end soldered to the pad and the other holding up.

• The main factors for erecting a monument consist of:

• Irregular thermal efficiency.

• Uneven solderability of components or PCB pads.

• Installing balanced out.

The generation of tombstones will certainly bring about poor item look and even impact the product
function.

Consequently, we require to take measures to prevent the occurrence of headstones.

3) Bridging

The solder joints are attached by solder, triggering a short circuit. The root causes of bridging
consist of:

• The opening of the steel mesh is not suitable.

• Way too much solder paste.

• Solder paste collapse.

• The reflow time is also slow-moving.

• The call stress between components and solder paste is undue.

4) Incoming Product Rejection

Incoming material rejection is among the common anomalies in SMT.

It is the failure of components or PCB pads to form a good connection with the solder. The major factors
include:

• Oxidation of elements or PCB pads.

• Surface issues of elements or PCB pads.

• Manufacturing process troubles of components or PCB pads.

Along with the typical abnormalities mentioned over, other anomalies may take place in the SMT
procedure, such as element lift, element change, missing out on, etc.

These abnormalities can additionally result in item top quality problems and should uncovered and
handled on schedule.

Summary

SMT procedure anomalies such as solder beads, headstones, bridging, and being rejected can bring about
product high quality problems.

In order to prevent item high quality problems, it is essential to handle SMT processes. Strictly
execute these specifications, reinforce the administration of tools, products, and examinations, and
thus minimize the event of item top quality issues. At the same time, PCB makers must continue to
develop new technologies to speed up PCB
assembly.