Assembling Prototypes and Small Series with the SMD Starter Production Line from Paggen Werkzeugtechnik

An increasing number of interesting ICs are only available in SMD packages today, and as electronic devices become more compact and functional, the packages of SMD components are also becoming smaller and smaller. With effort and a steady hand, most of these components can be soldered to a board by simple means even in a small laboratory, but as soon as prototypes or even small series need to be built on a regular basis, manual placement becomes too labor-intensive and the risk of assembly errors increases.
 
The SMD Starter production line from Paggen Werkzeugtechnik, consisting of a stencil printer, a manual placement machine and a compact reflow oven, is an interesting alternative for increasing your productivity in such cases.
 

Stencil printer SD240 with metal squeegee

Good preparation is half the battle, and of course, this also applies to working with SMD components. Normally, SMD components automatically move into the correct position during the reflow phase due to the surface tension of the liquid solder. Due to the ever decreasing spacing of components and the use of lead-free solders, the correct application of solder paste to the pads of the board is crucial for a good final result without time-consuming rework. Unfortunately, in practice, this is also the most difficult phase in the assembly process, as a good result depends on many parameters and environmental variables, such as temperature, consistency and age of the solder paste, flatness of the board, tension of the stencil, angle of the squeegee, pressure exerted by the squeegee on the board, and surface condition of the solder pads, to name just a few. Even fingerprints can cause problems. A number of parameters can hardly be influenced, but a good stencil printer like the SD240 makes it much easier to achieve good results.
 

When unpacked, the stencil printer feels solid and sturdy. The heavy metal baseplate and rubber feet make it very stable and prevent it from moving easily. The special clamping system and the clamping frame allow the use of metal and polyester stencils in different sizes. The intelligent positioning system eliminates the need for stencils and boards with alignment holes (and corresponding pins) or framed stencils. The template is secured with eight Allen screws. When I first used it, these screws were so tight that I could only loosen them with a fair amount of force. Once the stencil is fixed in place, you can tighten it with the two knobs on the front until the springs that hold the stencil under tension are compressed about a centimeter. The board is then placed on the metal plate under the template using six magnetic spacers. The spacers should be placed so that the board cannot move and the solder pads are approximately aligned with the holes in the template. It doesn’t have to be super precise. The stencil printer comes with a Plexiglas plate and a marking pen (lettering is removable) to make alignment easier. Optionally, you can also order a “laser light” on a stand for the same purpose. I have tried two different stencils and boards and managed quite well to align the board reasonably accurately to the stencil by eye. Then, using the buttons to tighten the stencil and the two dials on the right side of the printer, you align the board exactly to the stencil. Finally, you adjust the height of the template with the front and rear adjustment wheels so that it lies flat on the board when the frame is folded down.


 
The next step is to apply the solder paste with the metal squeegee. It is advisable to tape off the clamps holding the template with some masking tape. This avoids tedious cleaning work afterwards. By holding the squeegee at an angle of about 60° with moderate pressure, you apply sufficient solder paste in an even motion. For practice, you can make a test print on paper beforehand. Simply place a sheet of printer paper between the stencil and the board. The underside of the stencil should be cleaned regularly. For small stencils, the supplied squeegee may be less useful. A Japanese or classic spatula is often more suitable here.
 

My first boards with the stencil printer were almost perfect, with a few minor imperfections now and then. Nevertheless, I know from experience that the board will be perfect after the reflow process. Practice makes perfect, even with a stencil printer.

Manual placement machine PlaceMAN

PlaceMAN consists of a metal frame with adjustable board holders and a vacuum pipette that can be moved manually in the horizontal and vertical directions through two mechanical guides that also serve as wrist and arm supports. The vacuum pipette can be moved down and up and rotated with the knurled knob at the top of the handle. The pipette is equipped with what is known as a Luer/Lock connection, which is particularly common in the medical world. This allows you to use unlimited standard dispensing tips with the PlaceMAN, should the supplied dispensing tips and aspirators be insufficient or lost. Four warm white LEDs on the underside of the pipette provide even illumination of the work area. A low-noise, specially adapted aquarium pump provides the necessary vacuum, with suction manually adjustable via a valve. Details have also been thought of: there is a grounding point for ESD protection and an integrated storage box for dispensing needles and suction cups.
 
Placing components is simple and quick. You position the pipette above the loose component and then slowly push the pipette down with the knurled knob until the part is firmly sucked up. Now move the pipette to the place on the board where it is to be placed and lower the pipette again. If necessary, you can rotate the component. When it is perfectly in place, use the button on the pipette to press it down onto the board. Continue to press the button of the pipette down until you feel a stop that turns off the vacuum. Now you can move the pipette up again. For very small components, it is sometimes not necessary to push the button through to interrupt the vacuum, as these adhere sufficiently to the solder paste and are automatically released from the pipette when it is raised.
 

The suction force should be adapted to the size of the parts to be placed. Different components require dispensing tips with different diameters, with or without suction cup. It is advisable not to press the dispensing needle too firmly onto the pipette to allow for easy changeover. To avoid frequent changes, it can be useful to mount multiple boards and populate them all at once in order of component size. I was able to pick up very large components like an RJ45 connector with magnets or an ESP32 module easily. Even a 0603 resistor was no problem at all. Large components like the already mentioned RJ45 connector or some electrolytic capacitors are better placed manually with tweezers, since the pipette does not always reach high enough above the board surface with them.
 
In contrast to placing components with tweezers, the PlaceMAN’s wrist and arm rests reduce the risk of accidentally moving previously placed components on larger boards. You don't have to turn the board constantly to reach everything. However, a steady hand and good vision are still necessary.
 
The basic version of the PlaceMAN that comes with the SMD Starter production line has few accessories. You need at least one additional SMD tape feeder for the placement to work smoothly. This is available as an accessory in various designs, but can certainly also be assembled or 3D- printed by yourself. For this review, I made a tape feeder from laser-cut 3- mm plywood.

For right-handers, the metal handle of the tweezers rests well in the hand and handling is comfortable. Left-handers will probably have a bit more difficulty working with the PlaceMAN. The metal handle of the pipette has two threaded holes for an optional dispenser. With a bit of skill, you could also use these holes to attach a small USB camera. One complaint is that on the unit I tested, the LED illumination flickered when the pipette was moved. On closer inspection, this seemed to be due to a bad solder joint of the power cable on the LED board.

Reflow oven HR-10

 

The HR-10 reflow oven not only looks solid, but is also compact and takes up little space with dimensions of 36 x 50 cm (width x depth). Four R7stype 1-kW halogen lamps serve as heaters. Through the metal fan in the center of the lamps, hot air circulates through the oven. The drawer is equipped with two threaded rods on which there are four movable board holders with low thermal mass. When the drawer is opened, two fans ensure accelerated cooling of the freshly soldered PCB. The scope of delivery of the reflow oven also includes a tablet from Lenovo together with a protective cover and a type K thermocouple. I did not try out the tablet, as I do not expect any surprises here, and the HR10LF app also ran on my smartphone. Operating the oven is simple and straightforward, both via the front panel or the app.
 

When the reflow oven is switched on, you are prompted to open the door and close it again. When closing, the door is audibly locked with a click and a short preheating cycle begins. After that, you are prompted to open the door again, and a short time later the oven is ready for operation. For a first test, I used the reflow profile recommended by Paggen for lead-free soldering. I also specifically used some larger components like SMD electrolytic capacitors, since these are sometimes soldered less well in infrared ovens. The first test was successful, but since the temperature was a bit high anyway, I adjusted the reflow profile in the app a bit and set a preheat cycle of 160 °C for 60 s and a reflow cycle of 220 °C for 15 s. With these settings, my second attempt was quite successful. Here I had used yellow tantalum electrolytic capacitors, among others, as a test because they discolor quickly at too high temperatures. Of course, you have to adjust the values a bit depending on the color of the solder resist (e.g., matte black absorbs more heat than green), the presence of ground points and the number of layers of the board. The next three boards with various components, this time for a real product, also came out of the oven perfectly soldered. With the included thermocouple, you can measure the temperature on the board during the reflow process. To fix the thermocouple on the board, you have to use some temperature resistant Kapton tape. It is a bit unfortunate that the thermocouple is only for temperature measurement and cannot be used to control the reflow process right away. This might be an idea for a future software update. The temperature inside the oven is controlled by periodically switching the halogen lamps on and off. The total power consumption reaches a peak value of just under 3.5 kW, which is slightly higher than the power stated in the manual and on the device. In standby mode, the power drops to about 60 W. Given the power consumption, it is advisable to connect the reflow oven to a power outlet with its own fuse protection.
 

In addition to reflow soldering, the oven is also suitable for drying. For this purpose, you can set special temperature profiles. I tested the drying of material by regenerating silica gel with orange indicator: The result was perfect. There was only a bit of condensation in two places: at the bottom of the drawer (near the two cooling fans) and at the height of the small window. Drying SMD components while waiting for a reflow process and annealing Plexiglas after laser cutting are other possible applications. Even when the oven is used for several hours, the outside remains cool. If a profile is set for drying, the oven does not preheat when switched on, but immediately prompts you to place the material in the tray and close the door.
 
The app is simple and intuitive to use. After the first start, the reflow oven is searched for via Bluetooth and then paired. A total of 100 temperature profiles are available, which can be selected and edited both via the app and via the display and buttons on the reflow oven.

 

There is also a demo mode, so you can get an idea of what the app is like without having a physical reflow oven around. I sometimes had problems with occasional error messages in Slovak, and the Bluetooth connection sometimes dropped, but the latter could also be due to my smartphone occasionally falling asleep. Since the HR-10 has a manually operated drawer, the reflow or drying cycle itself cannot be started via the app. To do this, you simply close the drawer and then have to follow the instructions via the app or the LCD screen.
 
All in all, the HR-10 is a solid and intuitive reflow oven that delivers good results. Reflow soldering of PCBs is quite fast at about two minutes. Including the cooling cycle, it’s more than six minutes. If you want to solder many boards with it, it is recommended to buy the optional FE10 solder fume extraction.