We’re kind of surprised we haven’t covered this concept before since it only uses techniques that are commonly avaialable for home PCB fabrication. [Ray] made this solder paste stencil out of a sheet of copper using the same etching techniques you would for a circuit board. He designed and printed a resist pattern, with toner everywhere except the places where there should be holes in the stencil. He transferred the toner to the copper using an iron.

The difference here should be obvious; this a thin copper sheet with no substrate. Because of that, you must protect the copper surface before etching. he covered the entire thing, both sides, in packing tape. After that it’s into the Cupric Chloride bath to dissolve the exposed parts. Once the tape and toner has been removed you can scree a precise amount of solder paste onto your boards.

This isn’t for everyone, but if you’re assembling many boards it’s not a bad approach. If the stencil is no longer used it can be recycled, but we do wonder how corrosion on the copper will affect the stencil’s performance.

The idea for this technique came to [Ray] from a guide that’s been around for years.

Make sure those tiny parts know their place by using this surface mount solder assistant (translated). It’s like a clamp for small packages; gravity and a needle to hold them in place while you do some hand soldering. [Red Devil] started the built by soldering together some brass rails into a hinged frame with a clamp to accept the needle tip. Next, a pair of tubes were added to accept LEDs which light the work area (we think that’s a fantastic touch). Finally, the assembly was mounted to the corner of a square base that makes up the work surface.

This is basically a complex version of a simple gravity clamp. But if you’re doing some assembly line soldering this would be indispensable. For this kind of work, custom jigs are often built. That would still be the case, but this armature removes the need of building something into each jig to hold the SMD components in place.

A hard drive crash, and some other happenings that aren’t entirely clear to us, led [Devbisme] to put in a parts order. As he wanted to make the most of his shipping costs, he decided to fill out the order with parts that he’ll use eventually. He’s been working with surface mount designs and wanted to move from using resistors with 0805 packages to the 0603. Having nothing on hand, he devised a way to account for almost all standard values with the fewest number of different resistors.

That’s a mouthful, but what he actually did was figure out what combinations of resistors can best be wired in parallel to achieve a different standard resistance value. This way, if he doesn’t have a specific value he can solder one 0603 surface mount resistor on top of another one to get there. He ended up writing a Python program to best calculate this set of values. It came up with a set that lets him synthesize 159 of the 168 standard resistor values within +/- 4% using just 19 actual resistor values. His method requires anywhere from one to three resistors to get to each value. Soldering three 0603 packages on top of each other might not be the most fun, but it makes for easy parts inventory management.

[Augusto] wrote in to tell us about his keychain-sized persistence of vision project. He built the original prototype on some protoboard, using a PIC 16F627 to drive eight LEDs. Synchronization is managed by a tilt sensor on the board that starts the strobing to match the direction the board is traveling. This is a similar setup as the POV device that used an accelerometer, but it should be quite a bit easier to code for the tilt switch.

Once [Augusto] had the hardware dialed in he set to work laying out a surface mount design. The two AAA batteries were traded for a single 3V coin cell, which is on the back side of the board you see above. This is his first attempt at working with surface mount components and we think he did a great job. Check out the POV in action in the video after the break.

Need to use that antiquated hardware that can only be connected via a parallel port? It might take you some time to find a computer that still has one of those, or you could try out this USB to Parallel port converter. It’s not limited to working with printers, as the driver builds a virtual parallel port that you should be able to use for any purpose. But what we’re really interested in here isn’t the converter itself, but the build process. [Henrik Haftmann] posted a three-part series of videos on the assembly process, which you can watch after the break.

The build is mostly surface mount soldering with just a handful of components that need to be hand soldered. The first of his videos shows him stenciling solder paste onto the boards. From what we can see it looks like he built a nice jig for this using scrap pieces of copper-clad which match the thickness of the PCB, and hold it and the stencil securely in place. There’s a bunch of other tips you can glean from the videos, like the image seen above. It’s a clamp that holds the PCB and USB jack together while they are soldered.

If you’re ever thinking of assembling a bunch of boards you should set aside thirty minutes to watch them all.

[Thanks Panikos]

Drag soldering works exactly as its name implies, by dragging a bead of solder across fine-pitch pins you can quickly solder an entire row. The method relies on clean joints, so liquid solder flux is often used to make sure there is good flow. But if you’re drag soldering on boards that you’ve etched yourself the solder can sometimes run down the trace, rather than staying where you want it. Professionally manufactured boards don’t have this problem since they have solder mask covering the copper that doesn’t need soldering. [Ahmad Tabbouch] has a method that uses Kapton tape to act as a temporary solder mask on diy boards.

The process involves several steps. First, three strips are place horizontally across the board, leaving just a portion of the upper and lower pads exposed. Those pads are then tinned with solder, and a light touch with an X-acto knife is then used to score the tape covering the vertical rows of pads. Once the waste as been removed, two more strips are added and those rows are tinned. From there the chip is placed and soldered as we’ve seen before; first tacked in place, then fluxed, and finally drag soldered to complete the connections. This achieves a crisp and clean connection, presumably without the need to clean up your solder mess with solder wick.

Kapton tape resists heat, making it perfect for this process. We’ve also seen it used on hot beds for 3D printers, and as a smoothing surface for sliding mechanisms.

[via Dangerous Prototypes]

[Caleb] needed to use some surface mount components when prototyping. Instead of buy a breakout board he made one himself without doing any etching. The process he shows off in the video after the break uses copper tape to layout the traces for the board. It’s quite an interesting method which requires a sharp knife and a steady hand.

He used regular protoboard as a substrate and applied a layer of copper tape on the side without copper pads. From there he poked holes for the DIP pin headers. Now it’s time to do some cutting. [Caleb] removed the band of copper that would fall in between the pins of the surface mount device. He then tacked it in place with one dot of solder and drew the traces from the part to the pin headers. After removing the part he cut out the waste in between each line he drew with marker. What he’s left with is a set of thin traces that connect each pin of the surface mount component to the corresponding through-hole pin header.

This is very time-consuming, but then again so is soldering jumper wires to small-pitch components.

Hackaday writer [Gerrit Coetzee] built a simple clamp to aid in surface mount component soldering. This cheap, easily made device uses gravity to hold tiny components in place. The tip of the bolt is pointed, but gently like a ballpoint pen so as not to harm the components with a sharp tip. Roughly position your component, rest the tip of the clamp on its center, then nudge for final positioning. [Gerrit] also points out that this acts as a heat sink, helping to prevent damage to the component if you’re too lethargic with the soldering iron.

It seems like this device has been around in one form or another for quite a long time. But the best ideas do keep on popping up. Another nice tip to go along with this one is the use of a dowel when ironing during toner transfer for your PCBs.

Using an electric skillet to reflow surface mount circuit boards is a popular alternate use for those kitchen appliances. The real trick is monitoring and controlling the temperature. [Mechatronics Guy] built his own skillet temperature controller using a thermistor, a solid state relay, and an Arduino.

He was inspired by [Ladyada's] work which used a servo to adjust the temperature dial on the skillet’s power supply. This started by attaching the thermistor to the bottom of the skillet using JB weld. since this area will be heating up he also attached a terminal block for connecting the feed wires as the heat would melt any solder joints. Those wires travel back to a control box housing the Arduino and solid state relay. To gain finer control over the heating element the relay is switched on and off, resulting in low-frequency Pulse Width Modulation, which should help maintain a consistent temperature better than just turning the temperature dial on the cord.

Pair this up with the vacuum tweezers hack and you’re on your way to a surface mount assembly line. If you want to see this process in action check out this post. It goes from stenciling, to populating, to reflowing in a toaster oven.

[Thanks Rob]

We got a hold of some DS3232 RTC chips in a 20-pin SOIC package. We’d like to have one that is breadboard compatible for easy prototyping but when we searched for SOIC20W breakout board artwork we found none. We used Eagle to design our own and you can see the finished product above which we made using the toner transfer method and cupric chloride.

You’ll find the artwork after the break in case you need to make your own breakout board some day. If you know of surface mount breakout board artwork that is freely available please leave the link in the comments for future use, or send it to us on our tips line and we’ll add it to the post.

Incidentally, the DS3232 is the same as the DS3231 used in the ChronoDot but with the addition of some SRAM. We’ll let you know if we come up with an interesting project for it.

Update: We added 28 SSOP to DIP artwork submitted by [Paul Dekker]

20-PIN SOIC to DIP

28-pin SSOP to DIP [Thanks Paul Dekker]

Do you have access to a laser cutter? If so, you can use [Riley Porter's] method to cut your own solder stencils. He starts with the Eagle files and exports the Dimension and tCream layers to a PDF. That file is then processed using Ghostwriter, Gview, and finally, Corel draw. The result is a 1200dpi file to feed to your Epilog laser. Now you’re ready to stencil on the solder paste and populate the PCB.

[Thanks Travis Goodspeed]

Above is a video detailing one method for populating a two sided surface mount PCB. We covered using a stencil to apply solder paste for a PCB a few weeks ago. In the comments there was a debate about the virtue of using stencils as well as a question about how two sided boards are populated. This was a good question because reflowing a board twice can cause components on the underside to fall off.

[Wim L's] comment mentions that there are a couple of methods for two sided population. In the video you will see that a stencil is not being used, but instead, paste is applied by a pedal actuated syringe. The paste is applied to the underside of the board first, then a teeny dot of epoxy is added to hold the component in place. Each part is then positioned normally and baked in a reflow oven. This process both reflows the solder, and cures the epoxy. When the board is reflowed a second time, the epoxy holds the bottom components in place as the top solder reaches its melting point.

This method of applying solder paste is slower than using a stencil. But if done correctly, every component can get the amount of solder needed.

[rgbphil] has done a great job detailing how he built his Microdot wristwatch.This project is a lot more approachable than the pong watch we saw last month. If you’ve made a few printed circuit boards, but haven’t yet tried working with surface mount component, this is a great way to give it a try.

The parts count is pretty low, a few switches, resistors, capacitors, LEDs, a watch crystal, and a PIC 16F88 microcontroller.[rgbphil] is using a charlieplex so that a separate shift register is not needed to drive all of the LEDs. He goes into detail about the process of laying out the circuit. Some of the problems he encounters include how to manage all of the charlieplex connections in a simple way, how to program the chip once it’s on the board, and how to layout the controls for the device.

The display looks great in the video we’ve embedded after the break. We’re going to add these components to our next parts order and make this project part of the plan for getting us through the long cold winter ahead.

Let’s face it friends, everything is moving toward surface mount components. We’ve seen quite a few features here that cover using stencils to populate boards and using ovens to reflow. [Oleg] has put together a tutorial on the process he uses to populate and reflow his own boards.

[Oleg] is the creator of the USB Isolator and therefore has a need to frequently populate the same board. He’s using an acrylic frame that fits the PCB perfectly to hold it in place so that paste and be applied right up to the edges of the board. He ordered a laser cut Kapton stencil for applying the solder. The paste is squeegeed into the stencil holes, the stencil is removed, and parts are placed with tweezers and a steady hand. For the final step, the boards go into an old toaster oven for reflow.

[Oleg] uses temperature marker on his boards to monitor the progress of the reflow. This marker is basically a crayon that begins to melt at a specific temperature. When the board has cooled, the melted mark can be scraped away or removed with alcohol.

Of course this is only really useful if you have a bunch of high-quality boards to populate. But with the relatively low cost of getting professionally made boards we think the need for this type of assembly process is on the rise.

We’re big fans of surface mount parts. SMD components are cheaper, take less board space, and don’t require drilling; all the coolest new parts are only available in SMD packages.

Smart Tweezers are an advanced multimeter tool specifically designed to test and troubleshoot SMD circuits. It automatically identifies resistors, capacitors, and inductors, and displays the relevant measurements. Advanced Devices sent us a pair of Smart Tweezers to review. We used them while building our last few SMD projects, read about our experience with this tool after the break.

Tool overview

Smart Tweezers are a multimeter that measures resistance,  capacitance, inductance, and voltage with tweezer-like probes. The probes are shaped to hold loose SMD components, or test components already soldered to a PCB. Measurements are displayed on a small graphic LCD that reverses for left or right hand use. If you’ve ever tried to measure SMD components with a typical multimeter, the value of the tweezer profile is immediately apparent.

Starting at $300, this tool is intended for professionals who regularly debug, test, or repair SMD electronics. It’s a bit out of reach for a hobbyist who just wants to salvage SMD parts.

Using it

We tested the Smart Tweezers while developing three recent SMD projects: the DIY digital picture frame, the Bus Pirate version 1, and an upcoming ethernet device. It’s a real headache to debug an SMD circuit with typical multimeter probes: balance the probes on the correct pins, ensure that the probes don’t create momentary contacts that aren’t due to soldering, and then hold this position long enough to get a good measurement. This only gets worse if you have to repeat several times. The Smart Tweezers test SMD components with a quick single-handed squeeze.

The Smart Tweezers’ graphic menu is navigated with a simple jog wheel. The tool turns on with a press of the jog wheel, and turns off automatically after an adjustable timeout. The default auto-measurement mode attempts to detect the type of component and chooses the best properties to display, but auto-mode is a bit slower than setting a specific measurement mode.

Resistance

Every multimeter measures resistance, a typical multimeter has several test ranges that are toggled manually. The Smart Tweezers measure resistor values between 0.1Ohm and 5MOhms, without manual range adjustments. In the photo we’re measuring a 390ohm, 1% resistor.

Capacitance

Capacitance measurement is a feature that’s found on some high-end multimeters. The Smart Tweezers measure capacitance between 10pF and 499µF. In the photo we’re measuring a 27pF, 5% capacitor commonly used in a crystal oscillator.

A measurement taken from a single capacitor shows its value. A measurement taken from a circuit board shows the total capacitance of all connected components and of the PCB itself.

Inductance

Inductance measurement is rarely found on a multimeter. The Smart Tweezers measure inductance between 1µH and 1H. We didn’t have an SMD inductor to measure, but we tried a through-hole inductor coil from a switch mode power supply.

Voltage

The Smart Tweezers also measure up to 8volts AC or DC. After navigating to the voltage mode, the Smart Tweezers beep until you flip a small, recessed switch in the side of the case. The switch is too recessed to flip with a fingernail, so we used a through-hole resistor lead.

In the photo we’re doing a quick check to make sure that a tiny SOT-23 LTC2631a digital to analog converter is properly soldered to an adapter board and receiving power.

Continuity/Open Test

The Smart Tweezers have a continuity checking mode that beeps to verify connections between parts. This is an easy way to make sure every leg of a large SMD chip is properly soldered, or to hunt for broken/damaged components.

Current

The Smart Tweezers don’t directly measure current consumption, but it’s easy to calculate using voltage and resistance measurements with the equation Ir=Vr/R.

A look inside

As with any tool, we can’t help but take it apart and see what’s inside.

The batteries are replaced by removing three screws and the front cover of the device. This view reveals the batteries, the LCD screen, a small piezoelectric speaker, and the back of the circuit board.

A single screw in the back of the case holds the circuit board in place. We removed the screw to expose the front of the circuit board. The Smart Tweezers are powered by a Texas Instruments MSP430F135 microcontroller and a half-dozen analog chips. The MSP430 line is well-known for low power consumption, and it’s a logical choice for a portable device. Most of the passive support components are size 0402 or smaller.

Conclusion

The Smart Tweezers saved us a lot of time constructing and debugging three surface mount electronic designs. A simple squeeze and test is much faster and easier than awkwardly probing tiny parts with our cheap multimeter. It’s so much easier, in fact, we could hold the Smart Tweezers with one hand and take all the photos in this article with the other; try that with a normal multimeter.

We think two small changes could make the tool even easier to use. First, a larger button would make it easier to switch to voltmeter mode without a wire or screwdriver.  Second, it would be really nice if it could be turned-on by squeezing the tweezers together, rather than pressing the jog wheel.

We really liked the automatic component detection and auto ranging, and the measurement speed is excellent. We appreciate that the tweezer tips are replaceable because we’re really hard on our tools.

If you’re a professional or student who does a lot of work with SMD electronics, a pair of Smart Tweezers can save you time by reducing awkward multimeter measurements to a simple squeeze. This fairly expensive tool is probably overkill for all but the most hard-core hobbyists, but if you derive income from electronics, like we do, Smart Tweezers can be really handy.