Fabbrica di PCB in Cina: come scegliere il giusto fornitore di servizi PCB2020-08-24
Fabbrica di PCB in Cina: come scegliere il giusto fornitore di servizi PCB
Pertanto, ti consigliamo di ordinare circuiti stampati ( PCBA ) dalla Cina. Hai inviato la richiesta e il file Gerber al fornitore e hai ricevuto l'offerta. Sbarazzati del primo shock causato dalla differenza di prezzo con la Russia, sei pronto per firmare un contratto. Devo visitare la fabbrica prima di iniziare a lavorare?
Absolutely! no doubt. If we are talking about large orders (up to 500 pieces), or even more information about “online” circuit board contract production, please do not place an order before visiting the factory. The cost of mistakes can be high!
Who is this article for
This article is useful for those who plan to visit factories to produce and assemble circuit boards in PCB factory in China, especially for selecting suppliers. She summarized my experience in similar jobs and told you what to look for.
I have combined the key requirements of quality assurance into “minimal packaging”. If some of them do not meet the requirements, you should seriously consider cooperating with the manufacturer. Other important but not basic factors, I call them “additional benefits.” Their absence is not important, but their presence will add some meaning to the factory.
Our goal is to choose a factory that can provide consistently high-quality products. If we talk about the production of printed circuit boards, then for China, the common enemies of high quality: greed and carelessness have added two specific enemies: dust and static electricity. We will “capture” them in all areas.
I must say right away that experienced electronic engineers are unlikely to find new or interesting things here. These materials are designed for managers and business owners.
How about the PCB factory in China
All PCB factories visited in China have roughly the same organization. Depending on the scale of the business, the plot can be located in one room or multiple buildings, but the technical process remains the same, including:
- Surface Mounted Module Workshop (SMD);
- Export component installation workshop;
- Testing, assembly, packaging;
- The component warehouse is not entirely a process, but an important place for quality assurance.
Your tour of the factory floor will proceed in this order.
Component workshop (SMD)
The heart of every PCB factory in China plant. This is where the surface mount device (SMD) is automatically installed. The main advantage lies in automation. Robot machines locate micro devices with amazing speed and accuracy. The fast movement of the manipulator and the flash of optical recognition are fascinating!
The process flow includes the application of solder paste, the installation of SMD components of different sizes, the oven and the final control.
Check dust PCB factory in China
The workshop must be equipped with air conditioning and prevent dust and dirt. The indoor air should be cool and dry. Only enter in work clothes: pajamas, hats and removable shoes. If shoe covers are not given at the entrance, you can turn around without wasting time. Look at the floor, in a decent factory, it is actually made of a dust-proof polymer coating. Go back to the corner and do the simplest dust test-put your finger on the surface. Your fingers should be kept clean.
The entrance to the workshop takes place through a special blowing room where you need to spin the jet. Don’t be surprised if you find a rusty fan and a big hole leading to the street next to such a camera. PCB factory in China
Enter the work clothes workshop through the blowing room
The electric discharge will “bite” you when you touch it. The force is enough to damage delicate electronic components. Therefore, in the factory, the “static” problem must be solved at the system level. Try to fully touch any machine with you. Ideally, the system will ask you not to touch anything, or you will be asked to wear special gloves. All conveyor workers must wear a grounded anti-static wrist strap. Remember, some lenses prefer to wear them on the ankle.
SMD workshop anti-static protection
Aerobatics is a special “column” that eliminates static electricity at the entrance of each workshop. The coming person puts his hand on it and waits a few seconds until the signal sounds.
Quality control of component installation
The third and final key point is intermediate quality control. In addition to solving the “static” problem, this aspect is important in all stages of production. There has never been too much quality control!
The minimum packaging should include a visual inspection at the exit and at least one automatic optical inspection (AOI). These machines sequentially scan the surface of the circuit board and find missing or incorrect component mounting, deformation, soldering defects, etc. No inspector can match them in speed and reliability! I do not recommend working with factories that do not have an AOI site, which can test 100% of the products in the stream.
Project AOI-Automatic optical control of the board after installing the components.
AOI Project-Automatically check installed SMD components
Ideally (I have seen this), automatic optical control is required after each process stage: at the entrance, after applying the paste, after installing the components, and after baking in the oven.
Workshop for installing socket (THT) components
Unlike SMD, the lead-out components are not soldered to the surface, but installed through holes on the board (THT-through hole technology). The organizational structure of this website will provide you with a lot of information about the factory!
Small factories only use manual labor. This is not bad in itself, but the productivity of manual welding is low (which will affect the manufacturing cost of large-scale orders), and there are human factors in the appearance of defects.
A good factory is equipped with a wave soldering furnace that can automatically seal the installed components. There are also conveyor belts and manual operations, but workers only “bait” the components by inserting their “legs” into the corresponding holes, and then remove the “tails” protruding from the other side after leaving the oven. It is faster and more reliable!
Mount the input components on the PCB before wave soldering
Install input components on the board before sending to the wave soldering furnace
The minimum packaging is the same: protection from dust and “static”, cool dry air, replaceable shoes and work clothes, and continuous quality control.
In order to get more benefits, please pay attention to work arrangements. The convenient location of tools, conveyor belts, air extraction in the workshop and good lighting are important factors that affect the quality of printed circuit boards. Stop and observe the workers: at what pace are they working, and whether they are eager to perform all prescribed operations on each workpiece.
I saw a factory where the duty of every (!) worker on the conveyor included checking the received parts. He carefully checked the circuit board, checked the soldering of the various components, and then started to operate.
PCB factory in China Test assembly workshop
The test of the finished printed circuit board is carried out in at least two stages:
The electrical control is carried out on a special shelf (usually, its production is another production line in commercial products, called “test fixtures”). He checks whether the circuit board is open, or whether there are unnecessary contacts.
Function control involves checking the performance of the main functions specified in the partially assembled product. For example, if you order a board with a GSM module, the functional test will include installing the SIM card, connecting the power supply, and running a series of tests on the computer.
Make sure to conduct electrical and functional tests on all 100% PCBs produced before production!
Controllo elettrico dei circuiti stampati
Controllo elettrico del PCB finito
Guardare le condizioni in cui si trovano. A differenza dell'installazione dei componenti, quest'area non richiede un'elevata pulizia e qualità dell'aria, quindi non è un crimine non avere aria condizionata e abiti da lavoro. Tuttavia, devi essere d'accordo sul fatto che le cattive condizioni di lavoro non possono migliorare la qualità delle merci! Pertanto, l'aria fresca, una buona illuminazione e l'ergonomia sul posto di lavoro saranno altri motivi.
Le fabbriche più “avanzate” sono in grado di effettuare test a lungo termine dei loro prodotti: armadi speciali e persino intere stanze possono simulare condizioni operative future, dove le apparecchiature lavorano ininterrottamente per ore, a volte anche giorni.
Make sure to check out the parts warehouse. The quality of the latter is very sensitive to two things: moisture and aging. Therefore, the warehouse must be equipped with a climate monitor to display temperature and humidity, and even better is equipped with air conditioning. If possible, check the date the component arrived in the warehouse. Components that have been used for more than 2 years are full of serious problems.
In addition to the workshop, the warehouse must have a dust-free floor.
Parts warehouse of PCB factory in China
This is what a good parts warehouse looks like
Pay attention to how the warehouse is organized. It is the number of digits signed on the rack, the container for storing the components, their degree of protection, the person and method of selection and assembly.
For example, I came across a factory where components are transported from the warehouse to the SMD workshop on the trolley. These people told me about dust prevention!
As far as the added value of the entire factory is concerned, it focuses on the overall quality of the process organization.
As you know, it is impossible to automate chaos. Therefore, the more systematic and automated factory work, the less chance of marriage. Are there marks on the floor? it is good. Does the workpiece move between parts on the conveyor belt, and does the machine equipped with the conveyor belt stop emitting signal lights? perfect!
Le buone fabbriche utilizzano l'archiviazione degli indirizzi nell'officina e spesso distinguono anche il colore delle divise dei lavoratori in base alla natura e allo stato del lavoro (anche il più interessante sono i lavoratori bianchi di "gestione"), e ogni posto di lavoro ha istruzioni e promemoria dei lavoratori .
Ognuna di queste sfumature può essere di per sé banale, ma combinate, questi piccoli trucchi creano quello che viene comunemente definito un sistema di gestione della qualità.