Sparkfun
Sparkfun Stencil and Solder Paste Class
02/12/09 07:29 Filed in: PCB | Solder Paste
Synopsis - These are notes and pictures I took when I was at the Sparkfun stencil and solder paste class in Boulder Feb 11, 2009. This article includes pictures of parts of the process, Livescribe notes with audio, and a short movie showing the swipe technique used by Abe, the production floor manager at Sparkfun.
The class was broadcast over live streaming, but apparently the audio was poor, so I have uploaded my notes which include audio that is pretty decent. Perhaps some of the questions might be heard that weren’t heard on the broadcast. These notes use Livescribe, so you can click in the notes anywhere and jump to that section of the audio and presentation.
After the presentation was over, it was hands-on time and I stopped taking notes and recording audio but did manage to take some pictures and one little vignette/movie whose link is down below.
I didn’t count the total number of participants but it looked like maybe 14-15 people attended; most from the Colorado area but one gent was from Oregon.
Overall impression - I’m not sure how you could really learn this topic without doing it hands-on and therefore, this article and any like it that shows solder paste and stencil techniques will always be lacking that element. If the Sparkfun guys lack anything in their presentation polish (they’re engineers after all!), they way more than make up for it in hard-core experience and their willingness to share their knowledge and facility with us to learn. These classes are excellent and if you ever get a chance to take a class at Sparkfun, DO IT!. (This is my 3rd - SMD soldering, Eagle schematic capture, and now solder paste.) Their PCB Layout class is coming up on March 11.
Below are some pictures from the hands-on session and a link to a short video on swipe technique.
If you click the pictures you’ll get an enlarged image.
Here’s the Sparkfun production floor where the class was held:
This is one of 3 stencil and solder paste stations we used:
The project was to stencil and populate a few of these single axis gyro boards from Sparkfun
The “frame” is just some dents and dings circuit boards which work well because they’re the right height and are good and square. Abe (Sparkfun production manager), usually lays down a couple strips of masking tape to help keep the target board slightly higher than the frame. He says the stencil will tend to sit better this way:
Here’s the board after it’s in the frame. You should block the open end with another dinged board in order help keep the stencil flat as you swipe it with paste later.
Initial alignment of the stencil. The stencil looks gold in these pictures, but it really had a stainless steel color:
Initial spatula sizing - get a putty knife that’s clean and that’s slightly wider than the holes in the stencil you need to cover.
Use a narrow putty knife to ladle out a small glop of solder paste:
Spread the paste on the application putty knife right along the end - you want form a clean narrow bead on the end of the application putty knife.
You should end up with a bead of solder paste that looks like this:
Lay the putty knife over the edge of the station so it doesn’t smear on anything. Then start in on the initial fine alignment of the stencil.
Abe said to use a light touch to position it during this stage. The thing I noticed was that when you had perfect alignment, all the holes in the stencil will turn bright silver. If you have any dark colored holes or any holes are partially silver and partially dark, you’re not aligned yet.
Using your weak hand (Abe’s left hand in this picture), anchor one end of the stencil. Press hard, but not so hard that you could make the stencil slip:
Get ready to grab the putty knife with your strong hand. Do not move the stencil:
Make the initial swipe. Start at a steep angle and swipe towards a lower angle. You hardly need to press at all on the initial swipe:
Here’s a movie of the 2nd clean swipe with some narration by Sparkfun’s Abe. It should only take two swipes. The more you swipe it, the more likely you are to move the stencil and have to clean everything and start over.
In that movie above, you can see the proper technique for lifting the stencil. Lifting it off is where most of the mistakes will occur. Any slight rotation as you lift will smear the solder closest to your anchor hand. Peel it up and make sure it’s completely clear of the board before you remove the stencil.
Students populating the surface mount components of the gyro board after stenciling:
Sparkfun’s Nate Seidle reminiscing over the 1985 reflow oven Sparkfun uses for all reflow soldering:
A student project going into the oven for reflow:
The Sparkfun 1985 reflow oven:
It was a fantastic class and our thanks go out to Nathan, Abe, Matt, Bob and Heather for their excellent help and support teaching us this process.
Landon
The class was broadcast over live streaming, but apparently the audio was poor, so I have uploaded my notes which include audio that is pretty decent. Perhaps some of the questions might be heard that weren’t heard on the broadcast. These notes use Livescribe, so you can click in the notes anywhere and jump to that section of the audio and presentation.
After the presentation was over, it was hands-on time and I stopped taking notes and recording audio but did manage to take some pictures and one little vignette/movie whose link is down below.
I didn’t count the total number of participants but it looked like maybe 14-15 people attended; most from the Colorado area but one gent was from Oregon.
Overall impression - I’m not sure how you could really learn this topic without doing it hands-on and therefore, this article and any like it that shows solder paste and stencil techniques will always be lacking that element. If the Sparkfun guys lack anything in their presentation polish (they’re engineers after all!), they way more than make up for it in hard-core experience and their willingness to share their knowledge and facility with us to learn. These classes are excellent and if you ever get a chance to take a class at Sparkfun, DO IT!. (This is my 3rd - SMD soldering, Eagle schematic capture, and now solder paste.) Their PCB Layout class is coming up on March 11.
Below are some pictures from the hands-on session and a link to a short video on swipe technique.
If you click the pictures you’ll get an enlarged image.
Here’s the Sparkfun production floor where the class was held:
This is one of 3 stencil and solder paste stations we used:
The project was to stencil and populate a few of these single axis gyro boards from Sparkfun
The “frame” is just some dents and dings circuit boards which work well because they’re the right height and are good and square. Abe (Sparkfun production manager), usually lays down a couple strips of masking tape to help keep the target board slightly higher than the frame. He says the stencil will tend to sit better this way:
Here’s the board after it’s in the frame. You should block the open end with another dinged board in order help keep the stencil flat as you swipe it with paste later.
Initial alignment of the stencil. The stencil looks gold in these pictures, but it really had a stainless steel color:
Initial spatula sizing - get a putty knife that’s clean and that’s slightly wider than the holes in the stencil you need to cover.
Use a narrow putty knife to ladle out a small glop of solder paste:
Spread the paste on the application putty knife right along the end - you want form a clean narrow bead on the end of the application putty knife.
You should end up with a bead of solder paste that looks like this:
Lay the putty knife over the edge of the station so it doesn’t smear on anything. Then start in on the initial fine alignment of the stencil.
Abe said to use a light touch to position it during this stage. The thing I noticed was that when you had perfect alignment, all the holes in the stencil will turn bright silver. If you have any dark colored holes or any holes are partially silver and partially dark, you’re not aligned yet.
Using your weak hand (Abe’s left hand in this picture), anchor one end of the stencil. Press hard, but not so hard that you could make the stencil slip:
Get ready to grab the putty knife with your strong hand. Do not move the stencil:
Make the initial swipe. Start at a steep angle and swipe towards a lower angle. You hardly need to press at all on the initial swipe:
Here’s a movie of the 2nd clean swipe with some narration by Sparkfun’s Abe. It should only take two swipes. The more you swipe it, the more likely you are to move the stencil and have to clean everything and start over.
In that movie above, you can see the proper technique for lifting the stencil. Lifting it off is where most of the mistakes will occur. Any slight rotation as you lift will smear the solder closest to your anchor hand. Peel it up and make sure it’s completely clear of the board before you remove the stencil.
Students populating the surface mount components of the gyro board after stenciling:
Sparkfun’s Nate Seidle reminiscing over the 1985 reflow oven Sparkfun uses for all reflow soldering:
A student project going into the oven for reflow:
The Sparkfun 1985 reflow oven:
It was a fantastic class and our thanks go out to Nathan, Abe, Matt, Bob and Heather for their excellent help and support teaching us this process.
Landon
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