PCB Technical - The first three inspection system of PCBA foundry

One of the most important aspects of the strength differentiation method of electronic product manufacturing service (EMS) manufacturers based on PCBA foundry is the measurement of product quality.

1. Electronic Manufacturing Service (EMS) and Development

For electronic manufacturing services (EMS---Electronic Manufacturing Service), ODM and OEM have become the main PCBA foundry production models. About 40% of the world’s electronic products are produced by outsourcing, and this proportion will increase. increase.

2. Customers' requirements for PCBA quality

Customers have increasingly higher quality requirements for OEM PCBA assembly. The main source is driven by the consumer market, but they all want to obtain high profits, especially in the OEM industry, where the profit rate is increasingly low and the quality requirements continue to increase. There is a sharp contrast. The assembly of PCBA is the basis of the complete electronic information product and an important part of the quality and reliability of the complete machine. It is different from the general component manufacturing, so it needs to be controlled in outsourcing.

3. Understanding of the important role of the three inspection system

The first three-inspection system is a management inspection activity. It is an activity to verify whether each link of PCBA OEM production meets the requirements.

Quality control records should be used as evidence. It is to control the defects of PCBA assembly and manufacturing in the process of manufacturing, supervise the realization of the concept of "products are manufactured", and focus on the establishment of stable, repeatable, and monitorable process control goals. Not a mass inspection.

So, what is the first item?

The first product is the first (part one) product to be produced for each shift or model product. First article inspection is to inspect and confirm the first product.

The first three inspection system is to pay attention to the specific performance of on-site quality, and the management of the main factors affecting the quality of the manufacturing process 5M1E (personnel, equipment, materials, methods, environment, measurement) to determine whether the production conditions can meet the final quality requirements of the product . Its purpose is to prevent batch errors and reduce risks.

The basis of the three inspection system is the first article, and the comparison standard for the first article is the agreement and confirmation of the correctness of the actual OEM product-the sample and the guidance document between the customer and the PCBA foundry. The correctness of the sample not only includes the correctness of the material, but also includes the correctness of the assembly (mounting and inserting) welding and the correctness of the electrical performance. For the consistency of customer guidance documents and samples, the document takes precedence. If there is no document, the sample shall prevail. At all times, everyone must follow this basic principle. This is a protection for PCBA foundries and a responsibility for customers. The purpose is to ensure and improve the quality of the goods, and avoid the occurrence of quality losses caused by the mistakes of both parties.

Fourth, how to implement the first three inspection system

The first article management method stipulates that in each production section, the first 1 to 3 PCBAs of the production batch that have passed all the processes in the section are to be confirmed for the correctness of the assembly materials, the correctness of the welding, and the integrity of the appearance. The purpose is to find out early. Various process problems in the production process to avoid batch failures. Generally speaking, the first production parts mainly include the first part of the placement section, the first part of the assembly section, the first part of the testing section, and the first part of the finished product, which can be increased or decreased according to the specific section of the PCBA foundry.

It must be implemented in each batch of any variety of production, especially the proofing PCBA and the first batch production of PCBA should be paid more attention. The quality line inspector shall conduct a special inspection based on the customer's original BOM and special processing requirements to confirm the compliance of the PCBA. It is necessary to abandon the practice of some PCBA foundries that convert customers’ original BOM into insert assembly material card + paste assembly material card for production, materials, and inspection, because it is very dependent on individuals and completely depends on the responsibility of the BOM conversion personnel Heart and the ability to understand PCBA, without systematic supervision and prevention, it is difficult to be foolproof for the large number of customers and varieties of PCBA foundries.

So what is the three inspection? The three inspections are self-inspection, mutual inspection, and special inspection.

The first is self-inspection. Production and operation employees conduct self-inspection on the products produced by their own workstations, and conduct self-confirmation by comparing work instructions, samples, etc., and find objections to be resolved by the production engineer immediately. The second is mutual inspection. The inspection of the produced products by the length or length of each section or the line preparation staff is also confirmed by comparing the work instructions, samples, etc., and the objections are immediately resolved by the production engineer. The third is special inspection. In-line inspection inspects the product according to the customer’s original BOM, special processing requirements, sample parts, etc., confirms whether the first product produced meets customer requirements, and determines whether the product meets the requirements of production technical documents. Evaluate whether production conditions and process parameters can mass produce qualified products. The PCBA that is OK for the "three inspections" will be retained until the end of batch production.

4.1 Control requirements for the first three inspections

(1) Whether the provisions of technical documents such as product drawings, process documents, BOM, special processing requirements, etc. are harmonized and unified.

(2) Whether the parameters, position, polarity, angle, etc. of the mounted components meet the requirements of the technical documents.

(3) Whether the quality of raw materials is qualified (welder color, appearance of components, positive and negative poles, etc.).

4.2 Identification and records

The first piece that has passed the "three inspections" will be marked on the product by the inspection and kept until the entire batch is processed and transferred to the next process. The purpose of identification and preservation is to be able to trace whether the first "three inspections" and the first "three inspections" have been missed when there are quality problems in the whole batch.

All personnel participating in the first "three inspections" should sign the "first inspection form", and the signatures should be neat and complete to preserve the traceability of product quality.

4.3 PCBA inspection content

(1) The condition of the solder joints ensures that the soldering is reliable and achieves good electrical performance. For example: wrong soldering, missing soldering (empty soldering), false soldering (fake soldering), cold soldering; continuous tin, less tin, more tin, voids, tin bead, tin dross, plugging; whether there is thermal damage to the welding part, Copper skin, tin crack, etc.

(2) The condition of materials and parts, to ensure the correctness of the loaded materials, and to install them in place. For example: wrong parts, reverse, missing parts, tombstones; multiple parts, mixed materials; poor installation, floating height, offset, too long pins, no feet, etc.

(3) PCB situation to prevent bad printed boards and potential failures.