Another zone includes soldering crucible that holds up to 400 kg of solder. Two jets form proper wave that having contact with a board, creates solder joints of all elements.
It’s best if electronic components are arranged in parallel to the direction of solder wave flow in the soldering unit. The joints formed this way do not tend to create short-circuits on the board.
All parameters of the soldering unit are precisely controlled to ensure maximum efficiency of this process. Among controlled parameters are: the amount of flux applied, temperature in all heating zones, the capacity of pumps responsible for the size of the wave that washes the board, as well as oxygen level, because soldering takes place at inert nitrogen atmosphere. With this atmosphere (the level of oxygen is minimized to about 0.2%) flux is activated more efficiently, there is less pollution, solder’s surface tension is increased improving menisci in the soldering joints.
The use of nitrogen also makes the whole process more economical as the amount of melting loss (solder oxides formed during soldering) has been reduced. In the old hall, where soldering was carried out in free air, after an eight-hour shift 4,5 kg of melting loss was taken out of the soldering unit. Now, when soldering is carried out in the nitrogen atmosphere, the amount of melting loss is reduced to 1,5 kg per week (decrease of 95%). An additional advantage of soldering in nitrogen atmosphere is also reduction in consumption of flux.
Nitrogen is supplied to soldering units from central system that is connected to a large reservoir with gas in liquid phase located outside a production hall. This method of distribution of shielding gas is most efficient.
After soldering, laminate sheets (or boards) are cooled and get to the next stage of production of LPG controllers.
Optical inspection
Ready PCBs or sheets are subjected to optical inspection. It’s carried out in a device equipped with a camera, which by taking photos of the boards, checks the arrangement of individual elements, the polarization of diodes, individual solder joints (the shape of solder menisci which, when proper, ensures that there’s no cold solder – a cause of non-current).
The machine picks the boards that might not function properly. Each abnormality is verified by the staff. If it’s confirmed, photos of the damaged board are archived in a database and the product is repaired. After the board’s code is scanned, the person responsible for repairing the product gets the info about the character of abnormality from the device that carries out optical inspection. The board is repaired and proper information is recorded in the database.
Programming and testing
After optical inspection, boards are delivered to programming and activating stands. It’s equipped with testers copyright by AC SA’s structural studies department.
The processor of controllers is programmed first. After programming, a function test is carried out. It’s a simulation of the controller’s work in a car. Electrical signals appear which sometimes reveals damage to electronic components (impossible to detect during optical inspection). A board with broken electronic element goes to the service point where any such defect can be repaired with proper equipment.
Programming and activating stands were changed so that there’s no need to connect plug to the connector. Needle adapters are used connected directly to the joint’s pins on PCB. Thanks to this, connecting PCB before programming is done very quickly. Each stand also has code readers so test results are recorded in the database.
Lacquering controllers’ boards
The next step in the process of creating controllers is lacquering PCBs. It protects them from the weather, especially moisture. Protecting solder joints from oxidation is also important. An additional advantage of lacquering is the fact that varnish has adhesive properties. Electronic components gain additional connection with PCB which increases mechanical strength of the whole product.
Lacquering is carried out automatically in special devices – a form of XYZ plotter with a nozzle for spraying lacquer. This method compared to previously used dipping method is characterized by significantly lower consumption of varnish as it’s applied in exactly the right amount in areas that require it.
What’s more, the operation time of lacquering is shortened (compared to dipping method) as there’s no need to mask bulk connection on PCB that are later connected with the housing (it was required in the dipping method). In the case of spraying, head skips these spots.
Spray nozzle shapes lacquer that comes from it to a form of a curtain that properly wraps individual elements on PCB, creating a uniform film. It has appropriate width controlled every 20 cycles to ensure that boards are covered properly.
The curing of the varnish takes place in a furnace, at specific temperature. Then laminate sheets (if the product was produced in this form) are separated into individual boards. Technical margins are cut from those separate boards.
Pouring seals
Some controllers and pressure sensors are equipped with silicone seals, poured at special stands. The seal is suitable for use 24 hours after being poured on a cover or housing (the cover can be turned).
Assembling the controller
All production stages end with installing the controller – closing the board with soldered electronic elements in the housing.
Housings are bolted and sealed (including the connector), and labels are stuck onto them. There’s a special code stuck to the joint, linked in the database to a 2D code branded on the boards before the actual production process.
The final step is to check a controller for tightening screws, tightness, compliance of stickers on the housing. After this stage, the controller goes to the packing plant where it becomes part of gas system kits.
Other products of controllers production department
There are also other components of gas supply systems manufactured at controllers production department. Installation of gas level indicators, power source switches, temperature sensors and pressure sensors is carried out at dedicated stands.
Summary
Relocating production of controllers to new premises enabled the creation of a production line that eliminates troublesome transport of components between different areas. Previously, all stages were carried out individually in small rooms which meant that the products had to be carried from one place to another. By moving production to new premises and introducing small changes in some of the processes, production time has been significantly reduced.
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