Step-by-Step Guide to Quality Control

Many people think that QC is something that is done at the end of production before things are shipped out. Although this can be the case with shady production operations, a reputable supplier will never wait until the very end to confirm the quality of design, materials, manufacturing and logistics. A previous post on our blog discusses this in detail: How Quality Control Has an Impact on Different Production Stages.

Now let's dive into how we manage to maintain and surpass international ISO-9001:2015 standards.

A walk-through on the ISO 9001:2005 standard for quality control management system is also written in our Knowledge Base.

At each step, the workflows and the purpose of quality control are quite different. Therefore we divide our Quality Control processes into 4 parts:

1) IQC

IQC stands for Incoming Quality Control, which refers to the quality confirmation and inspection of purchased raw materials, components or products. That is, when the supplier sends the raw materials or parts, the quality is inspected by sampling, and finally it is judged whether the batch of products is accepted or returned. IQC is the first quality control checkpoint before product production. If the unqualified product is put into the manufacturing process, it will lead to the unqualified process or the final product, causing huge losses. Therefore, IQC not only affects the quality of the company's final products, but also affects various direct or indirect costs. How we handle IQC is a three step process:

1. Incoming Materials Inspection. Involves confirming the inspection standards required for incoming materials, and whether the materials meet these inspection standards. Separate good and bad products in different lots in storage.

2. Handling Identified Quality Issues. During the inspection process, quality problems will be tracked and dealt with immediately and quickly communicated back to the relevant departments. In order to combat similar future problems, we propose solutions and establish preventive measures quickly, and don’t avoid informing our clients about the current status in production. Material errors are not always bad and can be turned into a positive outcome if handled openly and efficiently.

3. Feedback on Quality Issues. We look at the nature of Quality Problems and see if they are random errors or systematic. We can always train our frontline staff to better inspect for random errors but if systematic errors cause trouble, we can end up taking that specific supplier out of our vendor list.

    

2) IPQC

IPQC refers to the quality control implemented in the process from raw material production to product packaging and storage (Hence why its called In-Process Quality Control). In this step, quality inspectors will conduct random inspections on the product quality of each process, check the operation methods and handling of the operators in each process, and check the contents of the control plan. And the inspector will analyze the problems found in the inspection, propose improvement countermeasures, and implement improvement strategies. The quality control of this process is mainly to make the process production fully meet the quality requirements of the product. IPQC, being the one with many inputs, makes up a 6-step process that involves:

1. Staff's Handling Procedures. Checking whether the operator wears proper work clothes, shoe covers, finger cots when in contact with the PCBA and other sensitive processes.
2. Machinery and Tools Security Check. This one is quite self-descriptive.
3. Material Placement. Check whether the materials (incoming materials, defective, QC-passed products, and products yet to be confirmed) are placed separately and easily identifiable. Confirm the placement of the materials for faster processing (direction, placement in the workplace, how far down the production line etc.)
4. Check Tools Handling. Check whether the operator works according to the requirements of the workflow and whether the method the tools are used is correct.
5. Testing Methodology. Check and confirm whether the testing method is correct (confirm according to the testing requirements), and whether the product passes the test.
6. Environment Control. Check and confirm whether the workshop environment is tidy and in compliance with 5S  (Sort, Set in Order, Shine, Standardize, Sustain)

3) FQC

FQC, or Final Quality Control is the act of comprehensively inspecting and testing the quality of the product after all the processes are completed to before the product is put into storage. It is also the final quality control work before the product is packaged or boxed. The quality control at this stage mainly focuses on appearance inspection and performance inspection. For example, color, gloss, roughness, burrs, whether there are scratches; physical or chemical properties of materials, electrical properties, mechanical properties, operation control, etc. The purpose of the inspection at this stage is to ensure that the product meets the shipping specifications and even meets the customer's requirements (Fitness for Requirement). Therefore, product defects of different degrees (serious, major, and minor levels) must be detected at this stage.

4) OQC

OQC, or Outgoing QC, refers to the shipment inspection carried out by the supplier in accordance with the standards agreed by the contract or order between the supply and demand parties before the finished product is shipped. The quality inspection at this stage mainly focuses on the packaging status, anti-collision materials, product safety labels, accessories (Accessory Kits), user manuals, product performance testing, outer box labels, etc., for comprehensive verification and confirmation. The quality inspection method at the OQC stage is mainly based on sampling inspection. Of course, for products with high unit prices or high grades, it is also very necessary to perform a full inspection of the overall condition of the product in the OQC stage.

In the FQC and OQC phases, NexPCB mainly inspects and confirms:

1. Functional testing. Confirming that circuit boards are performing normally and clipping/pivoting auxiliary parts are moving within the expected range.
   
   Our QC staff performing functional testing on a PCB using a test jig.
2. Packing List confirmation. First, we make sure that the packing list is complete, and nothing that doesn’t belong inside the product packaging goes inside it. We gently shake the boxes to check if there are any loose parts. Our packaging QC staff confirms that the product manual, and the warranty card is in neat condition, the language is correct, and the text is clear. After validating that the product label specifications and dimensions are correct, the text is clear and the product accessories are complete, with accurate specifications and quantities, we sign them off as passed.
3. Product Appearance. The PCB parts are complete (Confirmed with an optical test), and polarized components are in the correct direction. The solder joints are smooth and clean, no visual indicators of defective joints such as too little solder, missing solder, burns, and shorted pads.
4. Packaging Check. The packaging is the first aspect of the product your customers will see so it needs to signal quality upfront. Checking that the printing on the packaging is correct, the colors follow your Pantone specifications and the packaging is firm and undamaged, results in better quality handling. And then there are functional check-ups related to packaging QC such as barcode and sticker positions. Finally we confirm that the size and strength of the inner box and outer boxes are acceptable so that your products will be safe and sound enroute.

As a company that provides intelligent hardware solutions for hardware start-ups that are working on all sorts of previously unexplored solutions, NexPCB has always strives to provide its customers with strict Quality Control services. After understanding your product requirements, and the manufacturing steps involved, we tailor a QC strategy for your specific needs. We identify gamebreaker features that your customers value the most and make sure that their quality is strictly controlled along the production line. NexPCB can also help you devise a competitor QC strategy to see where they fall short, so that you won’t have to.

However we should also inform you that there is no such thing as a perfect QC and quality is better ensured within an acceptable threshold instead of giving every aspect of it zero tolerance. New Product Introduction (NPI) is a process that requires smart use of limited project resources and a limited time period to reach quantity targets. A zero-tolerance quality control outlook is at best a perfectionist idea.

After we know your acceptable scrap rate, ppm requirements and such, we will map out the thresholds in which your product quality can be maintained. 

In this process, the electronic and structural engineers need to confirm the technical rationality of the specifications and confirm the enforceability with the supplier. The QC staff needs to confirm the enforceability in the factory. The experience of the production line workers also play a pivotal role in detecting any non-obvious errors. Based on the above confirmation method, NexPCB verifies the original reliability and durability requirements, formulates production attention points and key control nodes, and complete quality standards for materials and finished products. The batch production follows with the same emphasis on quality that you see in the first sample you receive.