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Describe location and retention before naming the cause

Record whether the particle is at the middle of a chip body, near a termination, scattered around the board or associated with a particular paste deposit. Capture scale, component reference and board side. A retained particle and a loose particle may create different risks and require different disposition under the applicable workmanship requirements.

Do not brush away the first examples before recording them. The distribution can indicate whether material was squeezed under a body, separated during reflow or introduced elsewhere. If contamination is suspected, retain appropriate samples and avoid assuming every shiny particle is solder without supporting evidence.

Review the deposit before the component covers it

Inspect print definition, amount, position and stencil underside condition. A deposit extending too far beneath a chip body can be displaced during placement and later coalesce into an unwanted bead. Paste condition, stencil design and support all deserve review; no single aperture shape is optimal for every component and process.

Use solder-paste print measurements to compare volume and position by aperture family. An average across the whole board can conceal a small set of problematic deposits. Compare the actual design and measured print, not merely the nominal foil thickness in a purchase order.

Examine placement and stand-off conditions

Component seating, placement force, body geometry and board support can influence how paste moves before heating. Compare component lots or geometries only with an adequate sample and a controlled print. A change in body length or termination shape may alter the relevant inner deposit region without changing the schematic function.

Do not reduce placement force blindly or compensate for a poor print with a placement offset. The process must still place the component correctly and form the intended joints. Record the candidate mechanism and design a trial that can distinguish it from paste-volume or thermal effects.

Interpret reflow behavior within the material system

Paste slump, volatile evolution, coalescence and wetting behavior interact with the thermal history. Review the exact paste supplier's process guidance and measured product profile. Raising or lowering one oven-zone temperature without checking the product can trade beading for opens, poor wetting or damaged parts.

If the symptom is strongly concentrated at mid-body locations, use the mid-chip aperture comparison to investigate where paste is deposited. If small particles are distributed widely, broaden the investigation to paste handling, printing and material condition. These are hypotheses to test, not diagnoses generated from location alone.

Solder-bead observation rate

Count the defect with a stable denominator

Separate affected components, affected boards and total particle count. Ten particles may occur around one component, so particle count does not equal ten defective components. Define the inspection area, magnification, sampling and classification before comparing two process conditions.

The worksheet reports affected-component percentage and particles per affected component from your entered observations. If 12 of 600 inspected components are affected and 18 particles are counted, the results are 2 percent affected and 1.5 particles per affected component. They do not establish severity, electrical risk or process capability.

Correct and prevent through different actions

An approved removal or cleaning operation may correct a unit, but it must not damage terminations, mask or neighboring features. Reinspect afterward using the agreed method. Prevention requires a controlled change to the contributing print, placement, material or thermal condition and verification over a representative build.

Indium's stencil discussion provides examples of aperture-shape approaches used to reduce balling near passives. Those examples support an engineering trial; they are not universal reduction percentages or a replacement for the selected component's assembly guidance. Preserve adequate solder for both intended terminations while evaluating the unwanted particle.

What to send for engineering review

Include the component package, land and aperture artwork, stencil thickness, paste identification, print/placement evidence, measured profile and a defect map. State whether particles are loose or retained and what acceptance requirement applies. If the issue appeared after a change, include the previous and current controlled states.

The next page should follow the question: mid-chip geometry for inner deposit shape, bridging for an unintended conductive connection, or general defect triage when the particle's origin is still unclear. An enquiry can begin with incomplete evidence; explicitly naming the unknowns helps the team request the right information.

Turn a symptom into a controlled investigation

Record the first observation before cleaning, reheating or removing material changes it. Capture the assembly identity, location, process stage and inspection method. A clear photograph is valuable, but its lighting and viewing angle can also create misleading impressions about shape, color or attachment.

Confirm what has actually failed. A suspected bridge should be distinguished from a harmless-looking feature by appropriate examination and electrical context. A loose particle, an adherent bead and an unintended conductive connection require different questions. A surface appearance alone does not establish a cold joint or an internal separation.

Build a small set of competing hypotheses and identify evidence that could distinguish them. Material condition, deposited quantity, placement, heat history, movement and contamination may interact. Do not make the observed stage the sole cause: a problem first seen after reflow can originate earlier in printing or handling.

Compare affected and unaffected locations under the same observation method. Preserve denominators when reporting rates: boards, components, joints and particles are different counts. Define how many opportunities were inspected and whether repaired units are included. A percentage without this scope can conceal a change in sampling rather than a real improvement.

Contain material where the condition could affect the product, then evaluate a focused corrective action. Use the same measurement and acceptance basis before and after the change. A few improved samples can support an investigation, but they do not alone establish long-term process capability or reliability across every product variant.

For an enquiry, include the marked location, material and process records that are available, the failure symptom and the evidence required for disposition. State what remains unknown. The most useful result is an agreed next investigation or controlled process change, not a confident diagnosis generated from an isolated image or checkbox.