In the aerospace and defense supply chain, product quality isn’t just judged by samples — it’s judged by demonstrability. A solder joint that passes but cannot prove the procedure of creating it is still considered unqualified.

This article presents the specific requirements that cross-section must meet in these two areas, and the points businesses need to prepare if they want to participate.

1. Why are aviation and military the most demanding?

• No chance to fix: The product operates where regular maintenance is not possible, and errors can cause serious consequences.
• Very long life cycle: Equipment may have to operate stably for decades.
• Retrieve required materials: Each batch of materials must be traceable to the source.
• Process approval: The manufacturing process must be approved in advance, not just the product.
• Records may be inspected: Records are part of the product, not supplementary documents.

2. Specific requirements affecting cross-section

Note: specific requirements are specified by the customer or main contractor. Businesses need to take the list of applicable requirements from customers’ contracts and technical documents instead of assuming common standards.

3. What are the test records needed?

1. Sample information: Product code, batch number, related material number, manufacturing date.
2. Test information: cutting position, cutting direction, applied sample preparation process.
3. Results: The image has a scale, magnification, and measurement results for each criterion.
4. Applicable criteria: approved standards, quality levels, and thresholds.
5. Device information: Device code and valid calibration date.
6. Personnel information: implementer, checker, approver.
7. Abnormal recording: any deviation from the approved procedure, even if it does not affect the results.

4. Common traps when preparing documents

5. Sample preparation process needs to be stable

A point that gets little attention: in these two fields, the sample preparation procedure is considered part of the test and must be stable. Changing grinding consumables, cutting tools or molding material suppliers without notice may render the record invalid.

• Record the sequence of steps and materials used for each batch.
• Only change materials when there is a reason and after evaluating the impact.
• Maintain control samples between batches to detect process drift.
• Periodic training for people performing sample preparation.

6. Roadmap if requirements are not met

1. Compare actual requirements from contracts and customer technical documents, rather than assumptions.
2. Build internal processes based on standardized test methods.
3. Build report forms There are enough information fields according to profile requirements.
4. Set up a sample storage system Numbered and searchable.
5. Maintain equipment calibration and save complete documents.
6. Agree with customers about criteria, thresholds and test ranges before starting.
7. Evaluate testing room capacity and determine which tests need to be performed in an accredited laboratory.

7. Frequently asked questions

Is it mandatory for testing laboratories to be accredited?

Depending on customer requirements and product characteristics. Some tests are required to be performed in a qualified laboratory; some can be done internally if there is adequate agreement and control.

How long do records need to be kept?

According to the deadline specified in the contract or customer’s request. This period is usually much longer than for consumer products.

Can I use a saved sample from a previous batch instead of cutting a new one?

Not if the batch or process has changed. The saved form is used to answer questions that arise, not to replace current formative assessment.

Do grinding consumables changes need to be reported?

According to change control principles, reporting should be done when the procedure has been approved. Even if not required, recording helps keep records consistent and easy to explain when needed.

Where should I start if I want to join this supply chain?

From getting a complete list of customer’s actual requirements, then standardizing the procedure and application forms. These are two factors that determine responsiveness.

8. Conclusion

For aviation and defense, cross-section is not just a technical test but part of a quality proof system. Correct results are not enough — they must be accompanied by verifiable and traceable records.

Four things to do: get enough actual requirements from customers instead of assuming; standardize sample preparation and stability procedures; Build a profile form with enough information fields; and maintain sample storage system and calibration documents.

References

• IPC-TM-650 Method 2.1.1 — Microsectioning.
• IPC-A-610 — Electronic Assembly Acceptance Criteria.
• J-STD-001 — Requirements for electrical soldering and electronic assembly.
• IPC-6012 — Technical requirements for rigid printed circuit boards.

Related articles

• Cross Section in Automotive and Medical Devices: How the Requirements Differ
• IPC-TM-650 2.1.1: standard microsection procedure
• IPC-A-600 and IPC-6012: cross-section board acceptance criteria
• 7 situations where factories are forced to do cross-sections

Discuss further

Disclaimer

This article is an interpretive content compiled by us; not legal advice. Enterprises need to compare relevant documents/standards verbatim before applying them to specific products.

See more: Copyright Policy & Disclaimer by ticforall.com.

Void in BGA solder joints is the most controversial topic in electronic quality testing. One side considers every void an error; The other side believes that small voids are a normal characteristic of the procedure. Document IPC-7095 exists to provide a systematic review rather than a perceptive argument.

This article presents the leveled void approach, the correct way to measure it, and what to keep in mind when comparing measurement results with criteria.

1. What is IPC-7095?

IPC-7095 is a guide to the design and assembly of ball bearing components. Content related to quality control covers how to evaluate voids in ball solder joints, including classification by level and different treatments for each level.

Note on scope: specific numerical thresholds are specified in the body of the standard document. When applied to specific products, businesses need to compare directly with the standard and agree with customers.

2. Why is void not always an error?

Void forms naturally during the melting process: gases from the flux, moisture and air are trapped as the tin solidifies. So in reality almost every solder joint has a certain amount of void.

What determines whether void is a problem or not are three factors:

1. Size: Large void reduces local electrical and thermal conductivity.
2. Location: The void located in the area connected to the pad or in the bearing area has a much greater influence than the void in the middle of the tin block.
3. Distribution: many small, scattered voids are usually less serious; a large centralized void is the problem.

3. How to measure void properly

Indicating a percentage while ignoring size and location is an understatement and often leads to unnecessary disputes.

4. How does Void affect location?

5. X-ray and section when comparing criteria

Practical consequence: for the same ball, the void ratio measured by X-ray and the void ratio measured by cross-section may be different. This doesn’t mean one method is wrong — the two methods measure two different quantities. Therefore, the report must clearly state the method used.

6. Evaluation and reporting process

1. Determine the applicable level for the product and agree with the customer before measuring.
2. Use X-ray for screening and localize balls with large voids.
3. Cut the section at the questionable balls, with at least one reference ball.
4. Record three parameters for each void: scale, largest size, position.
5. Compare criteria by level and clearly state the conclusion for each cut ball.
6. State the limit of conclusion: applies to tested balls, does not generalize to all components if there are not enough samples.

7. Common points of dispute

• Difference between ratio measured by X-ray and by cross-section: Due to the nature of the two different measurements, it is not an error.
• Acceptance thresholds vary between customers: Written agreement is required before evaluation.
• Voids in different locations are treated the same: leading to conclusions that are too strict or too lenient.
• Evaluation from just one word: does not represent the entire row of balls or components.

8. Frequently asked questions

Is there a common void threshold for all products?

No. The threshold depends on the level of application, product requirements and agreement with the customer. It is essential to agree on thresholds before testing.

Do small evenly distributed voids need to be reported?

Reporting is recommended to have data to monitor process trends, even if results are still satisfactory.

Does Void progress over time?

It is possible, especially with components working at high temperatures. Void tends to spread with thermal cycles, so the assessment after the heat test has a different meaning than the assessment immediately after solder jointing.

Should I cut the entire row of balls to evaluate?

If the goal is to evaluate uniformity within a row, cutting along that row should be done. If the goal is to confirm a specific location, cutting in the right location is enough.

Can cross-section results be used as evidence?

Yes, the report clearly states the cutting location, measurement method, application level and includes a photo with a scale. These are factors that help verify results.

9. Conclusion

Void is a natural phenomenon of the solder jointing process, not a default sign of error. What needs to be done is a systematic assessment: measure all three parameters, consider the location, and compare with the agreed application level.

Four things to do: agree on levels and thresholds before measuring; Use X-ray for screening and section for confirmation; Record full scale, maximum size and location; and clearly state the limits of the conclusion according to the number of samples tested.

References

• IPC-7095 — BGA design and assembly.
• IPC-A-610 — Electronic Assembly Acceptance Criteria.
• J-STD-001 — Requirements for electrical soldering and electronic assembly.
• IPC-TM-650 Method 2.1.1 — Microsectioning.

Related articles

• Cross-section BGA: void measurement and head-in-pillow detection
• J-STD-001 and IPC-A-610: evaluation of solder joints through cross-section
• IPC-A-600 and IPC-6012: cross-section board acceptance criteria
• Cross-section QFN/DFN: void under the heat sink and solder pins
• Set of standards governing cross-section: IPC-A-600, IPC-6012, IPC-TM-650 2.1.1, J-STD-001 and IPC-A-610

Discuss further

Disclaimer

This article is an interpretive content compiled by us; not legal advice. Enterprises need to compare relevant documents/standards verbatim before applying them to specific products.

See more: Copyright Policy & Disclaimer by ticforall.com.

The two standards most mentioned when talking about solder jointing quality are J-STD-001 and IPC-A-610. They are often used interchangeably, but their roles are different: one specifies process requirements, the other specifies acceptance criteria for inspection.

This article explains how to use these two standards when evaluating cross-section solder joints, and what points to keep in mind for a well-founded conclusion.

1. Two standards, two roles

In short: J-STD-001 answers “how to do it”, IPC-A-610 answers “what is considered successful”. A good report should cite both when it comes to assessing causes and quality conclusions.

2. Quality level affects criteria

Both standards are classified by quality level, and the quality level determines the stringency of the criteria. Therefore, the conclusion “satisfactory solder joint” must always be accompanied by the applicable level.

3. Welding criteria evaluated through cross-section

4. Limitations when applying surface inspection criteria to cross-sections

IPC-A-610 is designed primarily for visual and optical inspection of product surfaces. When applied to cross-sectional images, there are three points to note:

1. The shape on the section depends on the cutting plane: same solder joint, cut in different position for different shape. Therefore, it is not possible to directly compare the shape on the cross-section with the description of the surface shape.
2. Some features exist only on the surface: for example, the gloss or color of the tin surface — things that cannot be read on the cut surface.
3. Some features can only be seen on the cross-section: metallic bonds, intermetallic compound (IMC) layers, internal voids — things the surface testing criteria don’t cover.

Correct usage: consider the cross-section as an additional data source, clearly stating which features are read from where, instead of trying to assign all surface criteria to the cross-section image.

5. Procedure for evaluating solder joints on cross-section

1. Determine the type of solder joint and the applicable quality level.
2. Determine cutting position and direction used, diagram included.
3. Read each indicator in the table in section 3 and record the results of each indicator separately.
4. Compare with criteria of applicable standards and levels.
5. Specify limits: The results only apply to the cut sample, to the selected cutting plane.

6. The role of J-STD-001 in cross-sectional assessment

When the section shows a defect, the next question is whether the defect is of process origin. J-STD-001 is useful at this step because it specifies process requirements: temperature, time, materials, and equipment control requirements.

• Compare actual thermal profile with process requirements.
• Check the type and condition of solder jointing materials and flux.
• Check device condition and calibration status.
• Check cleaning and post-solder joint treatment requirements.

7. Common errors when drawing conclusions

• Apply surface criteria to the cross-section image: leads to wrong conclusions because the two data sources are of different nature.
• No quality level stated: conclusions cannot be compared.
• Conclusion for the whole lot from one sample: a section represents only the plane itself.
• Skip design: has unusual characteristics in shape but conforms to the intended pad and stencil design.
• No reference to standards: The conclusion has no basis for comparison or defense.

8. Frequently asked questions

Is it possible to conclude “pass” based on cross-section alone?

Yes, for the cut sample itself and for the characteristics observed on that cut section. It is not possible to extrapolate to the entire lot from just one sample.

If the shape on the cross-section is different from that described in the standard, how to handle it?

Check the cutting position and direction first. The unusual shape is due to a different cutting plane, not necessarily a defect.

Which quality level should be applied?

According to customer’s request or according to applicable market. This level must be clearly stated in technical documents before production.

Is Void considered an error by the acceptance criteria?

Not automatically. It is necessary to consider the ratio, maximum size, location and requirements of the product. With heat-conducting or load-bearing components, the criteria are often more stringent.

What else should be checked besides the cross-section?

A combination of AOI or optical testing to evaluate surface characteristics, and electrical measurements to evaluate functionality is recommended. Cross-sections add a layer of information that the other two methods do not have.

9. Conclusion

J-STD-001 and IPC-A-610 are not interchangeable: one is about process requirements, the other is about acceptance criteria. When evaluating solder joints through cross-sections, it is necessary to clearly distinguish which characteristics can be read from the cross-section and what limitations this method has.

Four things to do: clearly state standards and quality levels in the report; Do not apply surface criteria to the cross-sectional image; Read each indicator separately and write separate conclusions; and clearly state the limits of conclusions according to the cut sample.

References

• J-STD-001 — Requirements for electrical soldering and electronic assembly.
• IPC-A-610 — Electronic Assembly Acceptance Criteria.
• IPC-TM-650 Method 2.1.1 — Microsectioning.
• IPC-7095 — BGA design and assembly.

Related articles

• Cross-section solder joint: wetting angle, fillet penetration and intermetallic compound (IMC) layer
• IPC-A-600 and IPC-6012: cross-section board acceptance criteria
• IPC-7095: void criteria for level-specific BGA
• Set of standards governing cross-section: IPC-A-600, IPC-6012, IPC-TM-650 2.1.1, J-STD-001 and IPC-A-610

Discuss further

Disclaimer

This article is an interpretive content compiled by us; not legal advice. Enterprises need to compare relevant documents/standards verbatim before applying them to specific products.

See more: Copyright Policy & Disclaimer by ticforall.com.

Two testing rooms do the same cross-section but give different results — the reason often lies not in the skills but in the procedure. IPC-TM-650 Method 2.1.1 exists to solve exactly that problem: standardizing how samples are prepared and how microsection testing is performed.

This article describes the role of this test method, the steps to be followed, and the control points that directly affect the results.

1. What is IPC-TM-650 and Method 2.1.1?

IPC-TM-650 is a set of documents that collects test methods for materials and electronic products. Method 2.1.1 in this set specifies how to perform microsection — that is, cutting, molding, grinding, and polishing the sample to observe the internal structure under a microscope.

Note on scope: detailed specifications (type of abrasive, abrasive sequence, pressure, polishing steps, photo requirements) are specified in the standard text. When applying, businesses need to compare directly with the standard instead of relying on indirect descriptions.

2. Why is process standardization important?

1. Results must be comparable: Without a standard process, it is impossible to know whether the difference is due to the sample or the method.
2. Destroyed samples cannot be redone: Making a mistake in the preparation step means losing the opportunity to observe.
3. Sample preparation can create spurious defects: Scratches, burrs, and fake gaps are all easily read as real defects.
4. Conclusions must be verifiable: The third party needs to know in what order the sample was processed.

3. Process steps

4. Requirements for samples and cutting positions

• The cut location must be representative for the area to be evaluated, do not choose based on convenience.
• The cutting direction must be appropriate with the structure to be observed: longitudinal cutting for through holes, perpendicular cutting of ball rows for ball-shaped components.
• Need control sample prepared under the same conditions to distinguish true abnormalities from normal features.
• Need a background image first to try if the sample will undergo subsequent environmental or mechanical testing.

5. Requirements for equipment and supplies

6. Common errors in practice

1. Skip the intermediate step when grinding: jumping from coarse to fine grain to save time, leading to deep scratches that cannot be treated.
2. Pressing too hard when grinding: causes burrs and deforms the soft metal layer.
3. Do not clean between steps: The remaining abrasive particles from the previous step create new scratches.
4. Grinding too deep: removal of the intermetallic compound (IMC) layer or thin coating layer to be evaluated.
5. Shoot at only one magnification: Missing overall information or missing details, depending on the magnification selected.
6. Do not record the performed sequence: results cannot be reproduced or interpreted in dispute.

7. Take notes so the results can be verified

• Cutting location and direction, with diagram or photo showing location on the product.
• Sequence of grinding and polishing steps performed.
• Magnification of each image and corresponding scale.
• Control sample information and background image, if available.
• Standards and quality levels are used to evaluate results.

8. Frequently asked questions

Is this procedure mandatory?

Depending on customer requirements and applicable quality system. In many cases, the reference to a standardized test method is a condition for the results to be accepted in dispute.

Is it possible to build internal processes yourself?

Yes, but should be based on standardized test methods and clearly state deviations from standards, if any.

Where to get detailed technical specifications?

Taken directly from the test method content in the standard document. This article only presents the general role and sequence.

Does a wrong mold have to be made again?

It often has to be done again, because the sample has been cut and ground. This is why it is important to prepare enough backup samples from the beginning.

Do I need to take photos at multiple steps?

Should be taken at important steps, especially before deep grinding. If a problem is detected, the photos from the previous step help determine whether the cause is in the sample or in the preparation process.

9. Conclusion

The value of the cross-section lies in the reliability of the results, and that reliability depends directly on compliance with the standardization process. A properly prepared sample gives results that are comparable, reproducible, and defensible in the event of dispute.

Four things to do: follow the grinding and polishing sequence, don’t skip steps; Control pressure at every stage; Full recording of cut position, sequence and magnification; and always prepare control samples under the same conditions.

References

• IPC-TM-650 Method 2.1.1 — Microsectioning.
• IPC-6012 — Technical requirements for rigid printed circuit boards.
• IPC-A-600 — Acceptance criteria for printed circuit boards.
• J-STD-001 — Requirements for electrical soldering and electronic assembly.

Related articles

• IPC-A-600 and IPC-6012: cross-section board acceptance criteria
• From rough samples to cross-section images: casting, grinding, polishing and etching
• 5 strange marks on the cross-section: distinguish real errors from phenomena due to sample preparation
• Measuring dimensions on cross-sectional images: how to set the ruler to minimize the error?

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Disclaimer

This article is an interpretive content compiled by us; not legal advice. Enterprises need to compare relevant documents/standards verbatim before applying them to specific products.

See more: Copyright Policy & Disclaimer by ticforall.com.

When evaluating a circuit board on its cross-section, the question “this board passes or fails” cannot be answered without clearly stating which standard is being applied. The two most commonly referred to documents are IPC-A-600 and IPC-6012 — and they are not substitutes for each other.

This article explains the scope of each standard, what to read on the board cross-section, and how the quality level affects the conclusions.

1. Two standards, two scopes

In short: IPC-6012 states the requirements, IPC-A-600 states how to determine pass or fail compared to that requirement. When a cross-sectional report cites only one of the two, the conclusion is often unsubstantiated.

2. Why is it necessary to read both when cutting samples?

• Avoid applying wrong criteria: Using bare board criteria to evaluate soldered boards is a common mistake.
• Assignment of responsibilities: the error is in the bare board belonging to the board supplier; Errors that arise after solder jointing may be part of the solder jointing process.
• Determine the correct quality level to apply: The same characteristic may pass at one level but fail at another.
• Make sure the conclusions can be compared: The report clearly states the standards and applicable levels so that a third party can verify it.

3. Reading indicators on the circuit board cross-section

4. How does quality level affect conclusions?

Since the same characteristic may pass at one level but fail at another, the section report must clearly state the applicable quality level. A “pass” conclusion without stating the level of application is an unverifiable conclusion.

5. Cut the sample on the product or on a separate test sample?

1. Coupon: used to evaluate the board manufacturing process, which can be periodically monitored in batches.
2. Cut on real product: correctly evaluates the area of concern, but destroys a product.
3. Combine both: Separate test samples to evaluate the procedure, cut products when needing to verify specific positions.

One thing to note: results on individual test samples do not automatically translate to the real product, because the placement conditions and hole density may be different. If only data from a single test sample are available, this limitation should be clearly stated in the report.

6. Common errors when presenting reports

• Standards and quality levels are not stated: conclusions cannot be compared.
• Mix bare board criteria with soldered board criteria: leading to erroneous conclusions about responsibility.
• Do not record cutting position and cutting direction: cannot be compared with other tests.
• Missing images at high enough magnification for the transition zone: miss small but serious defects.
• There is no control sample: Unable to distinguish true abnormalities from normal characteristics.

7. Procedure for reading a circuit board cross-section

1. Overall determination: number of layers, board thickness, hole position in cross-section.
2. Plated hole rating: continuity, evenness, whether there are cracks or not.
3. Contact ring rating: material excess, eccentricity.
4. Base material evaluation: separation, burning, impurities.
5. Compare criteria: Compare each criterion with the applicable standards and levels, clearly state the conclusions for each criterion.

8. Frequently asked questions

Can IPC-A-600 and IPC-6012 be used interchangeably?

No. One side states technical requirements, the other side states acceptance criteria. Both are needed for a full conclusion.

Can soldered circuit boards apply IPC-A-600?

Can be used for the board structure, but the solder joints must apply assembly standards. Mixing the two scopes is the source of many disputes.

Who decides the quality level?

Usually applied by customers or according to market requirements. It is important that this grade is clearly stated in the technical documentation prior to production.

Is it necessary to cut samples periodically, or only when there is a problem?

It is recommended to have a recurring plan in batches, especially with multi-layer and small-hole products. Periodic testing detects process drift trends before mass errors occur.

What if the board meets IPC-A-600 but the product is still defective?

Additional off-board factors need to be checked: soldering process, design, assembly stress and usage conditions. Meeting structural criteria does not mean meeting reliability requirements in all conditions.

9. Conclusion

Evaluating the circuit board on the cross-section is only valid when attached to the correct standards and quality levels. IPC-6012 tells the requirements, IPC-A-600 tells how to determine pass or fail — without either, the conclusion will be difficult to reconcile.

Four things to do: clearly state standards and quality levels in every report; Distinguish between bare board and soldered board evaluation; clearly state the location and direction of cutting; and present conclusions according to each indicator instead of a general conclusion.

References

• IPC-6012 — Technical requirements for rigid printed circuit boards.
• IPC-A-600 — Acceptance criteria for printed circuit boards.
• IPC-TM-650 Method 2.1.1 — Microsectioning.
• J-STD-001 — Requirements for electrical soldering and electronic assembly.

Related articles

• IPC-TM-650 2.1.1: standard microsection procedure
• Cross-section through-hole solder joint: when does the pin solder joint crack?
• J-STD-001 and IPC-A-610: evaluation of solder joints through cross-section
• Choose the cutting position and send the cross-section sample: one wrong step and you will lose the entire data set

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Disclaimer

This article is an interpretive content compiled by us; not legal advice. Enterprises need to compare relevant documents/standards verbatim before applying them to specific products.

See more: Copyright Policy & Disclaimer by ticforall.com.

In a set of cross-sectional images, not everything that looks strange is a defect. Cutting, casting, and grinding samples also create marks — and those marks can look a lot like real cracks, real delamination, or faulty solder joints. Mistakes at this point are doubly costly: the factory both goes in the wrong direction and loses credibility with partners when the mistake is discovered.

This article reviews five common strange marks, how to distinguish them from real defects, and what to control during sample preparation.

1. Five strange and common traces

2. General principle of distinction

1. Direction: Traces due to sample preparation are usually oriented in the direction of the cutting edge or grinding direction, not in the direction of structural stress.
2. By location: Traces due to sample preparation are usually located in the surface layer or at the edge of the sample, rarely deep in the material.
3. According to repetition: If you grind again and the mark disappears, there is a high possibility that it is a machining mark. The real error remains after resharpening.
4. By form: True defects often have clear edges, sometimes with associated secondary traces (oxidation, deformation, adjacent voids); Machining traces are usually clean, even, and unidirectional.
5. According to control sample: Compared with well-prepared samples, machining traces tend to be similar across many samples, while true errors are unevenly distributed.

3. Transition rim — the easiest place to get confused

The transition zone between materials is where many real defects are concentrated, but it is also where the grinding process easily creates burrs and drag marks. This is an area that needs to be observed at high magnification and compared with many samples before drawing conclusions.

Signs of burrs in this area: soft metal is pulled over the surrounding harder material, creating the feeling of an unusually thick layer of metal. If polished again at a lighter step, this layer disappears.

4. Control points when preparing samples

5. Checklist before concluding

• Re-sharpened and checked to see if the marks are still there or gone.
• Compared with the control sample prepared under the same conditions.
• Checked whether the direction of the trace was in the structural direction or in the machining direction.
• The possibility of abrasive grains or metal burrs has been ruled out.
• Observed at high magnification at the transition zone.
• Suspicious traces were clearly noted in the report instead of ignored or confirmed.

6. Frequently asked questions

How do you know if a crack is real or caused by cutting?

Grind again and observe. If the crack remains and its direction is related to the structure, it is a true crack. If lost or changed in the direction of grinding, it is a machining mark.

Could the gap between the coating and the surface be due to casting?

Yes. If the molding resin does not penetrate completely into the small gap, it will leave a gap that looks like peeling. It is necessary to distinguish by the shape of the void and the degree of filling in the adjacent area.

Is loss of intermetallic compound (IMC) layer a solder jointing error?

Not always. The intermetallic compound (IMC) layer is very thin so it can easily be erased when polished too hard. It is necessary to check for signs of chamfering at the edge and compare it with a sample prepared more gently.

How many samples should be used to make a clear distinction?

Three samples are a reasonable minimum: if the same mark appears in all three and all have the same orientation, it is likely to be a machining mark. Real errors usually do not repeat exactly the same way.

If still not sure, what is the conclusion?

Record the level of certainty in the report and clearly state the suspected traces, with on-site photos. An honest statement of uncertainty is more valuable than a definitive but wrong conclusion.

7. Conclusion

The quality of a cross-section report depends not only on image reading skills but also on sample preparation discipline. Machining traces can lead to wrong conclusions, and wrong conclusions lead to wrong corrective actions — much more expensive than the initial cost of properly preparing the sample.

Four things to do: always re-sharpen to confirm the mark; eliminate burrs and abrasives before concluding; Prepare at least three samples to evaluate repeatability; and clearly state points of doubt instead of over-confirming them.

References

• IPC-TM-650 Method 2.1.1 — Microsectioning, sample preparation section.
• IPC-A-610 — Electronic Assembly Acceptance Criteria.
• IPC-6012 — Technical requirements for rigid printed circuit boards.
• J-STD-001 — Requirements for electrical soldering and electronic assembly.

Related articles

• From cross-sectional image to root cause: 5 investigation steps
• Two Laboratories, Two Different Results: Why?
• From rough samples to cross-section images: casting, grinding, polishing and etching
• 10 circuit board defects can only be detected by cross-section

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Disclaimer

This article is an interpretive content compiled by us; not legal advice. Enterprises need to compare relevant documents/standards verbatim before applying them to specific products.

See more: Copyright Policy & Disclaimer by ticforall.com.

A good cross-section only answers the “what” question. The real question that gets a factory meeting is “why” — and the gap between the two is where many quality investigations go astray.

This article presents a five-step process from cross-sectional image to root cause, along with common mistakes and a set of criteria to know when the conclusion is strong enough.

1. Why is cross-sectional image not the answer by itself?

Cross-sectional images show the shape of the defect: where is the crack, what shape is the void, which layer is separated. But the same form can be caused by many different causes. If we jump to conclusions from the form, it’s easy to choose the wrong corrective action — and correcting the wrong area is more expensive than not correcting it.

Therefore, the investigation process must separate two things: describing the phenomenon, and tracing the cause. Step one is done by eye and microscope. Step two is made of data.

2. Five steps of investigation

3. Details of each step

Step 1 — Describe the phenomenon, not infer

• Record the location, size, and direction of each observed trace.
• Shoot at at least two magnifications: one to see the whole picture, one to see the details.
• Always take photos with the control sample at the same magnification.
• Do not use words that describe the cause in this step.

Step 2 — Identify the failed floor

Structural errors on circuit boards typically fall into one of four levels: substrate material, metal plating, solder joints, or component bodies. Determining the correct floor will localize the supplier and related process.

Step 3 — Build a hypothesis and assign a timeline

For each trace, list all the moments in the product life cycle that could have been created: material acquisition, solder jointing, paneling, assembly, testing, transportation, use. Then gradually eliminate based on the nature of the trace — for example, cracks with oxidized edges are difficult to form in the final step.

Step 4 — Compare process data

This is the step that distinguishes between speculation and conclusion. Data to compare: heat log of solder jointing furnace, contact time, number of re-solder jointing times, change of material supplier, change of machine parameters, clamping force and tightening torque.

Step 5 — Verify with control test

The conclusion is only as strong as it is reproducible: change exactly one variable, keep the rest constant, and see if the phenomenon appears as predicted. If it cannot be reproduced, it is necessary to reconsider the hypothesis instead of drawing conclusions based on feelings.

4. Two typical examples

5. Common mistakes

1. Jump from photo to conclusion: Skip the data collation step because the results look too obvious.
2. Combine multiple causes into one conclusion: It’s generally written as “solder joint error” so no one knows what needs to be fixed.
3. Missing control sample: If there are no samples from the same lot, all comparisons are only relative.
4. Conclusion for the whole lot from one sample: a sample only represents itself.
5. Ignore the possibility of errors due to sample preparation: Fake scratches, burrs and gaps can be read as real defects.
6. Conclusion according to the requester: Choose the cause according to the ordering department’s expectations instead of according to the data.

6. Set of criteria to know if the conclusion is strong enough

• The specific failure floor has been identified, not just the general floor.
• There is a control sample under the same conditions.
• The hypothesis was verified by process data, not just by geometric inference.
• The possibility of error due to sample preparation was excluded.
• The phenomenon has been reproduced by controlled testing.
• Conclusions can be used to recommend specific actions for a specified step.

7. Frequently asked questions

How long does it take to walk all five steps?

Depending on the complexity and availability of process data. The most time-consuming step is usually step four, because process data is not always fully saved.

What if there is no process data?

It is still possible to narrow the scope using steps three and five: construct a hypothesis over time, then reproduce it with a controlled experiment. But the conclusion will be weaker and the limits need to be clearly stated.

Is it always necessary to find exactly one cause?

No. Many errors have multiple causes and effects. It is necessary to determine which causes are the main contributors and which can be intervened.

Which step is most often overlooked?

Step one. Many investigations begin with conclusions rather than with objective descriptions, leading to data collection in a predetermined direction.

When should an investigation be stopped?

Once there is a conclusion that leads to specific corrective actions and the corrective results can be verified with subsequent data. If this has not been done, the investigation has not ended.

8. Conclusion

Cross-sectional images are the starting point of the investigation, not the results. Its real value lies in the fact that it localizes the failure layer and provides a hypothesis that is specific enough to verify with data.

Four things to do: separate the description step from the inference step; always have a control sample; compare process data before concluding; and only end the investigation when the phenomenon can be reproduced under controlled conditions.

References

• IPC-A-610 — Electronic Assembly Acceptance Criteria.
• IPC-TM-650 Method 2.1.1 — Microsectioning.
• J-STD-001 — Requirements for electrical soldering and electronic assembly.
• IPC-6012 — Technical requirements for rigid printed circuit boards.

Related articles

• 5 strange marks on the cross-section: distinguish real errors from phenomena due to sample preparation
• Two Laboratories, Two Different Results: Why?
• 10 circuit board defects can only be detected by cross-section
• Why do solder joints crack after thermal shock test? Read the marks on the cross-section

Discuss further

Disclaimer

This article is an interpretive content compiled by us; not legal advice. Enterprises need to compare relevant documents/standards verbatim before applying them to specific products.

See more: Copyright Policy & Disclaimer by ticforall.com.

A conformal coating exists to block moisture, dust, and impurities from the circuit board surface. But when the coating doesn’t adhere well enough, it not only loses its protective effect — it also becomes a permanent site for moisture and impurities on the surface, causing the condition to deteriorate more quickly than if left uncoated.

This article provides instructions on how to read peeling coating and pad peeling marks on cross-sections, how to distinguish the origin, and what control points are needed in production.

1. Why does the coating peel off?

Coating adhesion depends on three factors: whether the surface is clean, whether the surface is dry, and whether the coating has cured properly. Without any of these elements, the coating may still look normal when first applied but gradually peel off over time.

2. Types of bubbles and how to identify them

1. Edge peeling: The coating separates from the surface starting from the edge or from the edge of the component. This form is often due to mechanical force.
2. Wide area: The coating separates into large patches, often related to thermal stress or residual moisture.
3. Local flaking on the solder joint: The coating separates from the tin surface but remains attached to the surrounding base material, usually because the tin surface has an oxide layer or flux residue.
4. Air pockets under cover: closed space between the coating and the surface, not completely separated but still creating a moisture path.
5. Flange according to component leg area: The coating separates around the base of the component, creating a gap that conducts moisture directly to the solder joint.

3. Marks to be read on the cross-section

4. Pad peeling and substrate material cracking

A related but more serious form of damage is pad shedding: the copper pad separates from the backing material, or the backing material cracks just below the pad. Two common mechanisms:

1. Excessive traction: When removing components, pulling wires or tightening connectors, force is transmitted to the pad and separates it from the material.
2. Cracking of the base material just below the pad: This form does not cause the pad to completely separate but weakens the bond, leading to an open circuit when additional thermal stress is applied.

On the cross-section, the second form is harder to see because the pad is still in the correct position. The telltale sign is a crack in the base material running just below the edge of the pad — which should be observed closely with high magnification.

5. Effects when the coating loses its effectiveness

6. Control points in production

1. Clean the surface before coating: This is the most important step and also the most overlooked.
2. Control residual moisture: Dry at appropriate time and temperature before coating.
3. Make sure it is fully frozen: Check the curing time and temperature according to the material manufacturer’s recommendations.
4. Avoid mechanical stress after coating: Check whether the post-coating steps accidentally impact the edge of the coating.
5. Periodic inspection by cross-section: Conventional adhesion tests do not detect air pockets under the coating.

7. Frequently asked questions

Is peeling coating always the fault of the coating material?

No. The most common cause is that the surface has not been cleaned properly or is still damp before coating. It is necessary to check the procedure before changing materials.

Is there a way to test adhesion without cutting the sample?

There are surface adhesion tests, but they only evaluate the coating at the test site, not detecting air pockets or local gaps underneath. The cross-section adds that information.

Are air pockets under the cover always at fault?

Not immediately. But it is a potential moisture conduit, and in highly humid or contaminated environments, it becomes a corrosion initiation point.

Can a bong pad be detected by normal testing?

Only when the pad has separated is visible. In cases where cracks in the substrate material under the pad are often not apparent, a cross-section or resistance test must be used.

Where should I focus on cutting?

You should choose areas with many pin components, the interface between the coating and the component pin, and the area near the connector — places that are most exposed to mechanical and moisture impacts.

8. Conclusion

The coating is only effective when it truly adheres to the entire surface. A small gap is enough to turn the protective layer into a permanent moisture trap, and the consequences appear late in the form of corrosion and electrical leakage.

Four things to do: control cleaning and drying before coating; Check the cross-section in the first batch to see air pockets and gaps; clearly state the location of the start of peeling to deduce the stress source; and incorporate environmental testing to assess actual effects over time.

References

• IPC-A-610 — Acceptance criteria of electronic assemblies, protective coating section.
• IPC-CC-830 — Standard for protective coating materials for printed circuit boards.
• IPC-TM-650 Method 2.1.1 — Microsectioning.
• J-STD-001 — Requirements for electrical soldering and electronic assembly.

Related articles

• What is Cross Section? Why do we have to cut samples to evaluate solder joints and circuit boards?
• 5 strange marks on the cross-section: distinguish real errors from phenomena due to sample preparation
• 10 circuit board defects can only be detected by cross-section
• Cross-section of crimp terminal and cable: compression, broken strands and gaps

Discuss further

Disclaimer

This article is an interpretive content compiled by us; not legal advice. Enterprises need to compare relevant documents/standards verbatim before applying them to specific products.

See more: Copyright Policy & Disclaimer by ticforall.com.