What is Acceptance Quality Level (AQL)

By Bester PCBA

Last Updated: 2023-08-01

What is Acceptance Quality Level (AQL)

Acceptance Quality Level (AQL) is a measure used in the electronic components and printed circuit boards industry to rate the quality of a product. It is defined as the maximum number of defective components or printed circuit boards in a delivery lot that can be considered satisfactory as a process average. The AQL value can be expressed as a percentage or in parts per million (ppm) and can refer to all or specific electrical characteristics or mechanical dimensions that are not met by the products in the delivery lot.

AQL is a key figure for evaluating quality optimization in PCB development and is defined under ISO 2589-1:1999 as a sampling method for component inspection. The acceptable quality level (AQL) is the worst quality level that is tolerable for a product. The AQL differs from product to product, and products that might cause more of a health risk will have a lower AQL. Batches of products that do not meet the AQL, typically based on a percentage measurement, are rejected when tested during pre-shipment inspections.

In practice, AQL is typically considered to be the worst quality level that is still considered satisfactory, while the Rejectable Quality Level (RQL) is considered an unsatisfactory quality level. The Indifference Quality Level (IQL) is somewhere between AQL and RQL. Different companies maintain different interpretations of each defect type, but buyers and sellers agree on an AQL standard that is appropriate to the level of risk each party assumes. These standards are used as a reference during a pre-shipment inspection.

Frequently Asked Questions

What Does 2.5% AQL Mean

AQL 2.5 refers to the acceptable level of major defective goods, which is limited to 2.5% of the total order quantity. If the defect level in the batch produced exceeds 2.5%, it indicates that the product quality does not meet the agreed standards.

What Is the Difference Between Level 1 and Level 2 AQL

Level 2 AQL is generally considered the standard, except for cases where the sample size is small. However, Level 1 AQL only requires 40 percent of the inspection level of Level 2 and is suitable for situations where less differentiation is necessary. On the other hand, Level 3 AQL requires 160 percent of the inspection level of Level 2 and is useful for minimizing the risk of accepting a lot with an excessive number of defects.

What AQL Level Is 100% Inspection

The ANSI/ASQ Z.14 standard recommends conducting a 100 percent inspection when the AQL sample size is equal to or greater than the lot size. Additionally, it is the responsibility of the supplier to perform a 100 percent inspection before an independent inspector conducts a secondary check on the goods.

What Does AQL 4% Mean

The AQL 4% refers to minor defects in a product. These defects may not significantly affect the product’s intended purpose, but they do not meet the specified standards. Despite these defects, some end-users may still purchase the product.

What Does AQL .65 Mean

AQL .65 refers to the minimum acceptable level of quality for a specific population or pre-determined sample size. To illustrate, if someone says “AQL is 0.65%,” it implies that they expect the overall defective items in the entire order quantity to be no more than 0.65%, on average, across multiple production runs with that supplier.

How Do I Choose My AQL Level

To choose your AQL level, it is important to take into account your product and market. For instance, if you are dealing with high-end products, lower AQL levels might be more suitable. Conversely, if you are dealing with lower-end products, higher AQL levels might be more appropriate. Additionally, it is advisable to adjust your inspection levels based on your relationship with the factory.

Is Lower AQL Better

The quality of a glove product batch is measured by AQL, which sets the maximum number of defects allowed in a random selection. Therefore, a lower AQL indicates higher quality and reduces the probability of defects.

What Is a Normal AQL Level

During a regular inspection, the AQL level typically falls between 0.065 and 6.5. The higher the AQL level, the more relaxed the inspection standards. For inspecting consumer products, the AQL level is usually established at 2.5, indicating no tolerance for critical defects, 2.5 for major defects, and 4 for minor defects.

What Is the Rejection Number of Sample Size 315 at 2.5% AQL

The rejection criteria for a sample size of 315 units with an AQL of 2.5% for major defects and 4% for minor defects are as follows: if there are 15 or more major defects and 22 or more minor defects, the lot will be rejected. This information can be found in Table 1 under the letter M.

What Is the Acceptance Sampling Size

The Acceptance Number (c) refers to the maximum number of non-conformances that are allowed within the sample. The Sample Size (n) is the number of samples that need to be inspected. Additionally, single sampling plans have a rejection number (r) that is always one non-conformance more than the acceptance number (c).

What Is an Example of Acceptance Sampling

Suppose you receive a shipment of 10,000 coffee mugs and decide to use acceptance sampling. You randomly select 28 mugs for inspection, and if the number of defective mugs is 0, 1, or 2, you can accept the entire shipment. However, if the sample contains more than 2 defective mugs, you must reject the entire lot.

Is AQL Sampling Random

AQL sampling involves selecting one or more samples randomly from the shipment and comparing them to a “golden” sample that is considered to be perfect. Generally, AQL sampling adheres to the ISO 2859-1 (or ANSI/ASQ Z1.4) standard for sampling.

Where Is AQL Used

AQL, which stands for Acceptable Quality Level, is a statistical sampling technique utilized in quality control to assess whether a batch of products satisfies a specific quality standard. Its primary objective is to guarantee that products meet the anticipated quality level and to avoid the delivery of faulty products.