How to Audit a Chinese PV Module Factory Before PO
Key Takeaway
A pre-PO module factory audit checks whether the line that will build your order can show process control, electroluminescence records, serial traceability, and a bill of materials that matches the certificate. It is a document collection with a line walk. It is not a score, and it is not a substitute for IEC 61215 and IEC 61730 evidence.
Table of Contents
When the Certificate and the Production Lot Are Different Facts
A module buyer is often ready to issue a purchase order with three files: a quotation, a datasheet, and an IEC certificate. Those files describe a commercial offer and a tested construction. They do not describe Tuesday’s layup station. The cell lot, the glass thickness, the encapsulant, the electroluminescence criteria, and the serial database are what the shipment will actually be. A factory visit that only walks a visitor aisle and ends in a conference room does not touch those records.
The pain is a lot that cannot be reconstructed. A later power claim needs a serial that matches a flash file and a bill of lading. Potential-induced degradation or a crack claim needs to know which materials were in that laminate. If the factory cannot open those links, the warranty conversation starts without evidence. Finding that out after containers sail is an expensive way to learn the quality system.
Audits also fail when they imitate a public factory introduction. A tour explains what a plant can show a guest. A pre-PO audit asks whether the purchase order in your folder will be built on a named line, against a named bill of materials, with records you are allowed to sample. The output is a gap list. It is not a numeric grade, and this agenda does not offer one.
A Buyer Agenda Tied to One Model Code
Scope the visit before anyone travels. Name the model code, the wattage bin, the bill of materials revision you intend to buy, and the factory address. Ask which production line will run the order, including whether lamination, framing, or packing is subcontracted to another site. If the answer is a different site, that site is the one you walk. Ask for a translator if work instructions are not in a language your team can read. A translated cover page stapled to a different body is something you can only catch if someone reads the body.
Documents before the line walk
Sit down with the certificate, the construction data form or the equivalent build list, the approved bill of materials, the station work instruction, and the calibration record for the sun simulator. You are checking identity, not decorating a report. The model on the purchase order should appear on the certificate scope or on a statement from the certificate holder that this variant is covered. The glass, encapsulant, rear cover, junction box, and frame called out at the layup station should match that build list. Write the revision codes. A mismatch is an open item, not a detail to settle after the deposit.
Write three names on the first page of your notes: the legal entity on the draft contract, the name at the gate of the line you will walk, and the holder named on the IEC certificate. They can differ. A trading company can sell, a factory can build, and a parent can hold the certificate. The audit does not forbid that structure. It forbids pretending the three are one name if you have not checked.
The line that will run the order
Walk incoming cells, stringing and bussing, layup, lamination, framing or edge finishing, junction-box attach and cure, flash test, electroluminescence, and packing. At each station, look for a controlled instruction and a way to identify the lot in process. A reject bin with no label, or a rework pile mixed with fresh laminates, is a note. You are not there to estimate a yield. You are there to see whether nonconforming product is segregated and whether anyone at the station is allowed to stop the line.
Ask to see the lamination recipe identity that the station is running, and compare the glass and encapsulant callout with the approved bill of materials. You do not need the factory’s cycle time, and you should not turn a stopwatch reading into a capacity promise. You need the revision code of the recipe and the material names.
Electroluminescence, flash, and a serial retrieval
Ask when electroluminescence is performed. A pre-lamination image can catch cracks before they are sealed. A final image before packing is the record that matches the serial you will see on site. Ask for the written criteria: what crack length, what dark area, what soldering defect is a reject, and who is allowed to pass a borderline image. Then ask to retrieve one image by serial from finished goods. If the criteria are only in an operator’s memory, or the image cannot be opened, that is a gap to close before the purchase order, not a story for the closing lunch.
At the sun simulator, record how the reference module is controlled and what the calibration label and procedure say. Do not treat a single flash you happened to watch as a power guarantee for the lot. The purchase order’s acceptance test, if you require one, is a separate clause with a sample size and a rule. The audit confirms the tool and the traceability of its calibration practice as written. It does not replace that clause.
Sample tests and change control
Agree in the contract which samples you may witness or send to a laboratory you name. A practical menu, to be selected against the risk you care about, includes visual and electroluminescence review, flash power against nameplate, and, when the contract requires them, wet leakage, insulation resistance, gel content, or peel strength. The audit day may only show that the fixture or the external lab path exists. Do not leave the visit with invented pass results. Leave with the sentence in the purchase order that names the test, the sample, and the accept or reject rule.
Change control is the other half of the bill of materials. Ask what document stops a silent swap of glass mill, cell bin, encapsulant, backsheet, junction box, or connector. Ask to see the engineering-change form, even a blank one. Then ask the certificate holder whether a change of that type stays inside the certified construction. If nobody can answer, the purchase order should freeze the bill of materials revision and require written approval before a change ships.
What to See, What to Take Away, What Not to Conclude
Use the table as the audit record. Each row has a takeaway you can file and a conclusion you are not entitled to draw from a short visit. Do not add a score column.
| Block | Look at | Take away | Do not conclude |
|---|---|---|---|
| Identity | Contract name, gate name, certificate holder | The three names, written down | That they are one company because the logo matches |
| Bill of materials | Station sheet versus construction data and approved BOM | Revision codes, or a written mismatch | That a showroom line is the export line |
| Lamination | Recipe identity and the glass and encapsulant callout | The recipe revision now in use | A cycle time or a capacity promise |
| Electroluminescence | Pre-lamination and final EL, plus the written defect classes | The criteria document and one serial lookup | A pass rate or a quality score |
| Flash | Simulator, reference module, calibration label and procedure | How calibration is identified in the procedure | That the module you saw flashed represents the purchase order |
| Traceability | One finished serial opened to lots and files | Cell, glass, encapsulant, rear cover, flash, EL, or a failed retrieval | A retention period that was not in a procedure you read |
| Nonconformance | Quarantine area and the NCR form | That the form exists and the area is physically separate | That rework is rare |
| Change control | Engineering-change path for glass, cell, rear cover, junction box | The rule that is supposed to stop a silent BOM change | That the night shift you did not see follows it |
Close the visit with two lists. The first list is records you actually saw, identified by revision or by serial, not by impression. The second list is gaps that block or condition the purchase order: a BOM mismatch, a missing electroluminescence criteria sheet, a serial that does not retrieve, a certificate scope that does not name the model, or a subcontracted process you were not allowed to see. Assign each gap to a person and a document that will close it. A verbal assurance in the conference room does not close it.
Pre-shipment inspection at the container is a different activity. It samples the finished lot against the purchase order. The factory audit samples the system that is supposed to produce every lot. Passing one does not pass the other. If you want both, write both into the order. Incoming inspection at your warehouse remains available as a last check of identity, visual condition, and, if you built it, a flash sample. It cannot recreate a material lot that was never recorded.
Language and shift coverage belong in the notes. If you walked only a day shift on a line that also runs at night, write that limit in the first paragraph of the report. If a process leaves the site, name the process and the address you did not visit. Readers of the report should be able to see the boundary of the evidence without guessing how thorough the team felt.
What a One-Visit Audit Does Not Prove
- It does not score the factory. A gap list is the result. A single number would hide which control failed.
- It does not replace IEC 61215 or IEC 61730. Type tests and a process walk answer different questions. Keep both files.
- It does not create a warranty. The warrantor, the term, and the remedy are the limited warranty. A hospitable visit does not add years to that PDF.
- It does not prove the night shift, a subcontracted site, or the next bill-of-materials change. Write the limit of what you saw. Freeze the revision if change control was unclear.
- It does not measure a yield or a defect rate. Do not publish a percentage you did not calculate from an agreed sample.
- It does not replace pre-shipment or incoming inspection. Those checks look at the lot you will pay for. Schedule them separately if you need them.
Bring the Model Code and the Certificate Scope
Share the model you intend to order and the certificate you were given. Weltrus will help you turn the gap list into purchase-order conditions: bill of materials revision, traceability fields, and the sample tests you actually need.
Frequently Asked Questions
Does a pre-PO factory audit replace the IEC 61215 and IEC 61730 file?
No. The certificate and its construction data describe a tested design. The audit asks whether the line that will run your purchase order is building that construction under a controlled process. You need both. A clean visit does not create a certificate, and a certificate does not prove which glass is on the line today.
What should an EL review produce?
A copy of the written defect criteria, confirmation of when electroluminescence is performed, and a check that images can be retrieved by serial. It does not produce a pass rate. If the factory cannot show the criteria or cannot open an image for a finished serial, write that as an open item before the purchase order.
What is a useful traceability test during a short visit?
Pick one finished serial in the packing area and ask the factory to retrieve the cell lot, glass lot, encapsulant lot, rear-cover lot, flash file, and electroluminescence file. If the record opens, you have seen the system work once. If it does not open, the purchase order should not assume serial-level traceability.
Which names have to match before you issue the purchase order?
Write down the legal name on the contract, the name on the factory gate for the line you walked, and the holder named on the IEC certificate. They may be three names. The audit does not require them to be identical, but it requires you to know which entity builds, which entity is certified, and which entity you can claim against.
Should the audit end with a numeric score?
No. End with a list of records you saw and a list of gaps that block or condition the purchase order. A single score hides whether the gap was a missing electroluminescence file or a missing fire extinguisher. This agenda does not publish a score.
