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
| Standard | Scope | Answer the question |
|---|---|---|
| IPC-A-600 — Acceptance criteria for printed circuit boards | Bare circuit board, no components installed | Does the printed circuit board meet the requirements in terms of structure and manufacturing quality? |
| IPC-6012 — Technical requirements for rigid printed circuit boards | Technical requirements that the board must meet | What requirements must the circuit board be manufactured according to? |
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
| Target | Characteristics to evaluate | Signs to pay attention to |
|---|---|---|
| Plated hole quality | Continuity and evenness of the plating layer according to depth | Localized thin plating, holes, cracks |
| Contact ring around hole | Excess material between hole edge and pad edge | Lack of material, drill hole deviated from the center of the pad |
| Copper layer thickness | Thickness of the copper layer on the surface and in the hole | Big difference between positions |
| Condition of base material | There are separations, burn marks, and strange impurities | Gaps between layers of material, discolored streaks |
| Borehole fluctuations | Straightness of hole wall according to depth | The wall of the hole is not straight and has steps |
| Corrosion level | Signs of corrosion on the surface and in the hole | The edges of the material are concave and have crystallized salt |
4. How does quality level affect conclusions?
| Quality level | Typical product type | Required level |
|---|---|---|
| Level 1 | Consumer products, basic requirements | Prioritize functionality, accept certain flawed characteristics |
| Level 2 | Industrial products, specialized equipment | Higher requirements on stability, more limited on allowed defects |
| Level 3 | Products requiring high reliability, critical equipment | The most stringent requirements, prioritizing continuous reliability |
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?
- Coupon: used to evaluate the board manufacturing process, which can be periodically monitored in batches.
- Cut on real product: correctly evaluates the area of concern, but destroys a product.
- 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
- Overall determination: number of layers, board thickness, hole position in cross-section.
- Plated hole rating: continuity, evenness, whether there are cracks or not.
- Contact ring rating: material excess, eccentricity.
- Base material evaluation: separation, burning, impurities.
- 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
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.
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