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By Richard Oakley
A PRINTED WORLD WE TAKE FOR GRANTED: THE MIRACLE OF THE SURFACE MOUNTED COMPONENT, PRINTED CIRCUIT BOARD.
Makar Technologies Ltd was established by Managing Director, Dave King, in 2015. This focussed, high-tech company is based in Forres and its objective was to develop in the Highlands. Currently employing twenty people, Makar has experienced a ten-fold growth in the last year. What do they do? They manufacture the modern-day miracle which we now take for granted – the surface mounted component, printed circuit board (PCB).
Practically everything in our age is controlled by a circuit board. Anyone who is aware of this technology will be astounded by the amount of functionality that can be placed on a board only fifty square centimetres in area, for example the British designed and built the £35 Raspberry Pi, ‘system on a chip’ computer, with thirty million sold globally.
Already armed with the knowledge that Makar is an innovative company; their contemporary building at the Enterprise Park in Forres, dazzling us in the crisp mid-morning sunshine, does not hint at its inner treasures; a huge investment of modern, cutting-edge equipment and working areas – with top-grade staff too.
The modern-day circuit board forms the heart of our modern world. It uses power coming from a battery source or the mains to control things we take for granted. For example, the PCB used to control a remotely controlled toy car. This toy car system will have two PCBs. The one in the hand control device will assess the direction the operator wants the car to drive, left, right, backwards or forwards or combinations of these. The directional request will come from a potentiometer (variable resistor) in the handset pushed by the operator and set to give an output between 0 for a no signal in that direction to a maximum one of 5 volts. This directional request will be calculated by a chip designed for this purpose and sent to another one that will transmit this information to the car. This part of the system will be powered by a battery with an on/off switch. On the car, the transmitted signal will be received by a receiver which may consist of several microcontroller chips. This will all be contained on a further PCB, again powered by batteries with an on/off switch. The directional information will be decoded and sent to a further chip that will convert the signal into a series of on /off commands that will be sent to motors controlling the steering and the drive motors turning the wheels.
Now for a tour of Makar’s factory – each area needs an in-depth explanation – and Marc Smith introduces himself. He is the customer program manager and he is also involved with business development and finding new markets – as well as being a Moray College/UHI graduate. “When we arrived in 2015, we just had a shell. The decision was taken to build and equip the space properly and correctly from the start and we started with the floor, this is suspended above the ground some 600mm and is designed to conduct static electricity away from equipment being manufactured and the operatives constructing it.” We were issued with anti-static overalls before entering the assembly area.
Dave King then joins us on our tour of the production facility so we can see how their boards are manufactured from start to finish. It starts with a block of four boards. They contain no components and will be separated out once all the components are assembled.
The unpopulated boards are fed into the production facility on demand by a magazine type device. From here they pass to a machine that coats the boards, where required, with solder paste, which is used to attach the surface mounted components in a later process. The blank PCBs are coated with Rosin and are green in colour with areas that are uncoated where the conductive tin coating is exposed, these areas are silver in appearance and have to be covered with the solder paste. A thin metal screen with holes in it corresponding to the areas requiring covering, is used like a silk screen in conventional screen-printing, it masks the board in areas not requiring paste.
The next stage of manufacture involves positioning the surface mounted components onto the board where the solder paste was applied in the previous process. The pick and place robot used for this can position between thirty and forty thousand components an hour, to an accuracy of one hundredth of a millimetre. The surface mounted components are fed into the system on ribbons so the robot doing the placing has to navigate between source and final position with an accuracy that positions the component precisely and uses a path which does not collide with any previously positioned piece.
Once all the components are placed, the board is then heated to cure the conductive solder before being washed in a solution that removes any excess. The final stage of the surface mounted section of manufacture involves checking the board using sophisticated visual recognition soft and hardware to check that each component has been positioned correctly with reference to the track layout and is of the required type and size. For example, surface mount, square, forty pin chips with ten legs per side could be mounted in one of four positions but only one pin is marked as pin one and this has to be aligned with the correct track on the PCB, otherwise the chip and board will not work correctly. Positioned sequentially in the manufacturing line is a machine that is used to assess the attachment of chips such as microprocessors that have their pins placed vertically below the component (most surface mounted components have their contact legs running horizontally out from the chip). This type of chip is very easy to damage while placing and this machine checks both the attachment and integrity of the device ensuring that no contact pins are squashed. This device uses x-rays to check the chip positioning, functionality and for solder voids.
Located at the juxtaposition between the surface mount board production area and close to where the through hole components are added to the boards sits Makar’s ‘ace in the pack’ – an infra-red rework station. This machine uses an IR beam to heat the component and is specifically used with BGA chips. A ball grid array (BGA) chip is a type of surface-mount packaging (a chip carrier) used for integrated circuits. BGA packages are used to permanently mount devices such as microprocessors to printed circuit boards.
The surface mount part of manufacture involves a range of highly advanced computer-controlled machines that are supervised by several skilled personnel. The next stage of manufacture involves the most sophisticated, highly evolved and competent assembly currently known to exist in the universe, the Mk1 human being! Attachment and positioning of all through-hole components is carried out by a group of extremely competent, communicative and pleasant individuals with the skill set to manage the complex hand-eye skills to position the through-hole components in this section of manufacture. A large number of these people started their careers in the RAF at Lossiemouth or Kinloss and have now transferred their skill set to work for Makar. I talked to an employee who was attaching a Mil Spec grade plug to a circular PCB festooned with a range of surface mounted control chips, with each of the plugs 20 to 30 contacts being carefully soldered to the correct hole in the board. Getting any contact wrong could spell disaster for the board and the system it was controlling. Each member of staff seemed to be surrounded with a number of the components they needed to attach, all positioned within easy reach but not cluttering the work area, swivel chairs seem to be a great aid to manufacture here.
Before leaving the manufacturing area we were introduced to Ljubomir (Head Design Engineer) who was ‘interrogating the quadrature signal of a DC servo motor’ to determine whether the machine was functioning correctly. This is displayed on an oscilloscope – the lag of one wave compared to the other indicating the direction of rotation and the wave frequency, the motor’s speed of rotation.
As we leave the production area Marc points out a line of plugs recessed into the floor and running parallel with the existing line of surface mount board production machines, these plugs indicate where a second line of production could be sited, I question how long a new line would take to order and install – the answer is six weeks! Makar has recently purchased a wave soldering machine as a further new investment in the facility. This machine develops a standing wave of liquid solder, the board is passed across this wave, attaching any through-hole component legs to the pads and hence the tracks on the base of the board.
Having some knowledge of several of the proprietor PCB generation software, I ask Marc what type they use? He says they are currently using Proteus but switching to Altium. Like all modern PCB generation software these examples are capable of converting schematic designs into printed circuit board layout, with the operator specifying the number of boards they want the final output to be spread across. I currently use a free version of these called Designsparks promoted by RS Components and sharing many of the features developed by Number One Systems for EasyPC, (the PCB creation software used at Moray College in their Electronics Department). Designsparks is linked into RS Components extensive range of electronic devises held in stock, giving the user a three-dimensional board layout, board component costs and availability.
The industrial sectors that Makar Technologies Ltd works results in having many vendor audits and they have always received the highest rating available, with some of their customers suggesting that their facility ranks amongst the best in the world.
Makar Technologies Ltd currently has a full order book and was working on projects to remotely control caravans and a stair-lift during our visit, Dave King says that if you require a system to be controlled, they can also provide the control electronics, actuators and computer systems to bring the project to life. They are what industry describes as a ‘turn-key supplier’, they do everything simply leaving the customer the starting key. Customers can have systems designed with or without any specification in mind. The Makar design team would then look to generate PCB designs, giving costing, functionality and future proofing suggestions before negotiating with the client the final design. This may or may not involve building prototypes for the customer’s approval. Makar’s engineers are capable of writing software for controlling system operation, for example, the firmware to control the speed and torque delivery of an electric motor. Makar are also currently looking to increase the functionality of their equipment by building smart intelligence into the equipment.
The fact that Makar employ twenty highly skilled people also shows that there certainly are employment opportunities in our own region, the Northeast, in the fast-developing high-tech sector. Simply, many young people are not aware of the great opportunities they have locally. Dave points out that there is a growing tech sector here and that the local colleges need to be catching up with local industry with relevant training. Though, at Makar, they provide comprehensive in-house training. If other companies follow suit and locate here, there may be less reason in the future for talented people to leave our area.
We have taken up enough of their time and they have been very hospitable. They are obviously proud of their spectacular facility and the contribution they make to the local economy by creating highly skilled and rewarding jobs in our community, as well as the contribution of their equipment to our fast-changing technological world.
Makar Technologies Ltd10 Forres Enterprise Park, Forres, Moray IV36 2AB. 01309 675837. www.makartechnologies.com
There is a vast global industry devoted to the manufacture of PCBs. The process has several stages that these days start with converting the schematic representation of a circuit layout held on paper into one in a modern PCB generation software package such as Designsparks. This schematic contains the linkage of the pins on the principle components such as surface mounted integrated circuit chips through resistors, normally used to control the current reaching different sub-circuits held on the chips themselves. There will normally be several Light Emitting Diodes (LEDs) on the schematic, these are used in the final circuit to indicate system function. All components will be linked directly or via other components to power and ground. The next stage is to convert the schematic into a PCB track layout, these days this is done automatically by the CADD software, this feature alone has saved £Billions of production costs. Different track thicknesses can be applied as required. At this point information transferred from the schematic is split into copper or silk layers. The track layout appears on the bottom copper layer. Information relating to the component type, size and position is contained on the top silk layer as is text and company logos.
For the purposes of this description we will assume that a four-layer board is being manufactured and to reduce costs several boards are being manufactured together on the set of blanks copper foils, adhesive and electrical insulating layers. This level of standardisation and amalgamation reduces costs while improving the quality of the final product. To aid manufacture the generating software will produce its output in an Extended Gerber output. The standard used is IS274X, this defines track thicknesses, pad layout, component rotation and solder masks. Prior to manufacture the production company will check that the pads, track widths and the smallest hole size conform to the required standard, any discrepancies will be rectified. At the manufacturing company each layer of the board will be converted into a transparent film one per layer in the final board at a one to one scale. The films have registration marks that allow alignment of them and the laminated boards. The manufacturing processes are set up as a sequential line with the correct light regime and ventilation for the stage of production.
On our four-layer board the two internal layers are manufactured first. The internal boards are formed from a laminate of epoxy resin and glass fibre core with two copper foils bonded to the outside of the insulating layers. This set of layers is bonded together in a clean room and photo resist/ultraviolet sensitive layers are attached to the copper foils. This is done under yellow light with ultraviolet (UV) light excluded from the system. Holes in the machine match those in the boards maintaining the original alignment. The next stage in the sequence involves overlaying the transparent films with a negative image of the two internal PCBs track and pad layouts, one is laid beneath the laminate and the second above, with the registration marks perfectly aligned.
Next the laminates plus film overlay are irradiated with ultraviolet light. At this point the photoresist layer is hardened on the copper outer foil where the negative image of the tracks and pads does not mask the board. This generates a positive image with the photoresist of the track and pads on the copper foil surface. Using a strong alkali, the unhardened photo resist is washed off the laminate exposing the copper not needed for tracks and pads to be etched off in the next stage of manufacture. Etching of the unwanted copper is done with a further strong alkali solution, during the process the thickness of the final track widths is measured to ensure their integrity. The final part of this process is to check all unwanted copper, that may short between tracks, is removed. Then the hardened photoresist is removed from the remaining copper tracks and pads.
The next stage is to physically punch the registration holes in the internal boards, but before this occurs the boards are checked automatically to ensure they match the required layout of tracks and pads, as the next stage permanently hides these internal boards from further inspection.
The outer layers are now bonded to the two previously produced internal boards. This is achieved by firstly laying down a heavy steel plate then an aluminium sheet, a copper foil, then two layers of glass cloth and uncured epoxy resin, before the two internal section are added, then the process is reversed. The complete assembly is indexed together and then placed with two other sets in an oven to be pressed together using a prescribed heating and cooling regime. The pressure forces the unbonded epoxy to the edge of the boards and the temperature ensures the correct curing. Although we are describing a four-layer board here complex boards used in defence and telecoms can be up to to fifty layer thick.
The steel and aluminium plates are recycled and the board is now drilled to ensure connectivity between all the track nets once the holes are coated with conductive material. The drilling is done using pneumatically driven drill spinning at speed s of up to 150,000rpm. The high drill speed generates very clean holes that can easily have conductive material bonded to them. The boards are drilled with an aluminium entry plate covering the top layer and an exit board preventing damage to the lower copper layer. The drill is computer controlled and the holes are drilled individually, meaning it is a relatively slow process, speeded up by doing three sets at a time. Drill changes are automatic. The entry and exit boards are replaced after being used.
Surrounding the PCBs is a margin of board containing bonded epoxy this area is now cut off using a CNC router. The cut path avoids damage to any of the required areas.
The next stage involves depositing copper in the drilled holes to ensure linkage of the nets on different layers. The process is completely computer controlled and involves dipping the boards in a series of cleaning, rinsing and deposition tanks. The boards are secured in a crane system that lower them into the correct tank for an appropriate period of time. The process deposits conductive carbon, palladium and copper (25 micron thick) into the hole walls.
Next the outer copper foils are imaged the process is similar to the one used on the inner layers but subtly different. This stage again occurs in a clean room with yellow light and involves the attachment of photo resist to the copper outer layer using a hot sheet laminator. The process involves a positive image of the track layout being positioned first followed by the PCB assembly and a second positive track image on top. The assemblage is then irradiated with ultraviolet light and the unhardened resist is removed this should be the track layout and it is now ready to be plated. The clear areas of the photo sheet are hardened and left un-plated, in contrast to the inner layers where the hardened areas were the areas we required. The boards are then checked to see all the photo resit that should be removed has been and that the copper tracking left is clean.
In the following stage the boards are electroplated with copper, the panels are securely attached with clamps to a crane system and electrically linked to it, so the boards forming the cathode of the system. This crane system plus PCBs are termed a flight. In the first stage the PCBs are chemically cleaned, in the next the copper is activated. The hole walls receive further electroplating, the aim is to deposit 42.5 microns of copper on the boards in total 17.5 from the foil and 25 from this process. Finally, the tracks and pads are coated with tin to make them resistant to etching. The outer layer is then etched to remove the copper between the tracks, the process is started by removing the hardened photo resist. The copper is etched using a strong alkaline solution, this is a conveyor system and the board is checked to ensure the process only cuts down and not sideways undermining the tracks. Finally, the tin is removed and the copper tracks only remain.
The next process of fabrication involves generating a solder mask on the board, this is the pad that the adhesive glue mentioned earlier is applied to at Makar. The first stage of this process involves coating both sides of the board with an epoxy green mask, this prevents short circuit forming between the tracks and the components. The boards are cleaned prior to the mask being applied. The board is held vertically and the mask is applied to both sides simultaneously completely encapsulating the board. The epoxy coating is then dried using a conveyor heater system. The board is then checked to ensure the integrity of the mask. Next the board is imaged and exposed to UV light, this is done using a two-draw-imager. The photo screen used is a positive image of the pads, the board is irradiated with the unhardened mask under the pads on the film strip being removed. The epoxy is further hardened using a conveyor heating system and the boards checked to ensure no epoxy mask is removed from the holes and the pads, as this would compromise the boards solder-ability. The final process of this stage begins with the copper pads being cleaned and activated, a layer of nickel and then gold is applied to them. The solder mask is applied using a crane system with the boards being suspended in a range of tanks to clean, activate and coat the pads.
The next process is too electro plate the edge connectors that are repeatedly connected and disconnected using hard gold. This is achieved by passing the appropriate connectors through an edge electroplating devise. This part of the fabrication must be specified with the order.
The penultimate part of production involves applying text, component symbols, (type locations and size) to the PCBs. This is done with an inkjet printer. This printing can be applied to the top and bottom of the board. If both sides require a legend then the board is passed under a conveyor heater prior to printing the second side. This process used to be done with silk-screens but this technique was time consuming. Finally, the boards are cured using a five-stage conveyor heating system which takes 5 minutes. Testing involves checking the integrity of each track net. A track net is a series of tracks and pads that are linked together, for example the power one would link between the direct current input and the electrically positive side of resistors and LEDs having one leg linked to that section.
The final stage is to cut the boards from the manufacturing block using CNC driven routers. Alternatively, the boards can be separated using a V-cut section. This cuts one third of the board thickness from both sides, it is preferred by some users because the PCBs can be completely assembled with components prior to splitting. Following a final cosmetic and mechanical check the PCBs are distributed to the client.