How to Surface Mount Solder Using Solder Paste

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About: I make things, sometimes they brake

Quick tutorial showing how to solder a Attiny85 package type SOIC-8 using a hot air tool and solder paste.

SOIC is just one of the many types of standarized packages that integrated circuits such as the Attiny85 can come in. The package type just indicates the components will look different and have the chip's legs accessible in different styles.

This is a free hand soldering paste technique using a Hot Air Soldering Rework Station but you are more than welcome to make a stencil from OSH Stencils!

Questions, Concerns , Compliments, Feedback all welcomed:

@NemesisContrer8

Step 1: What You Will Need

1. SMD291SNL ‑ Chip Quik Solder Paste (recommended to use because it comes w/ a fine tip syringe)

2. PCB board (I'll be using Adafruit's SOIC-8 breakout board)

3. Components being soldered (I'm using the ATtiny85)

4. Fine tip tweezers

5. Hot Air Soldering Rework Station/ Or a skillet,oven you feel comfortable using for SMD work

Step 2: Find Something to Hold Down the PCB

I'll be using my favorite vise the PanaVise 350 Multi-Purpose Work Center.

However , use whatever works best for you (small vise, tape, wood,clamp etc)

Step 3: Dispense Solder Paste Onto the Copper Traces

Squirt a line that spreads over the golden pads (copper pads)

Don't worry about getting the solder paste on the blue part of the PCB (solder mask)

Once the board is heated the solder mask will repel the solder paste to shrink & harden onto the copper pads

Step 4: Apply Heat to the Board

I used a the Hot Air Soldering Rework Station - Quick 957D under low air control at about 370°C

Alternatives include kitchen : skillets and small ovens just use with caution and continuous monitoring


The solder paste go through transitions from liquid-->dusty-->shrinking till it finally hardens

Step 5: Finished!

Here is the finished Attiny85 SOIC 8 pin package type soldered into the breakout board

-Happy soldering!

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38 Discussions

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ohoilett

1 year ago

Would that be too much solder paste for an SSOP or QFN package?

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Mjtrinihobby

1 year ago

This old electrical engineer just learned something new!

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TwistOneUp

1 year ago

Wonderful, and thanks NemesisC!

Most of the smd device datasheets I have seen state a max of 250C in the reflow oven settings. I have a reflow workstation with adjustable airflow and temp settings, and have to mount a SOT-23 on a DIP breakout adapter. I'm wondering if I need to go up to 370C, so I'll be trying 250C. I think the trick will be to set the airflow at just enough to melt the solder but not strong enough to push the breakout board out of my panavise.

I would also like to mod a toaster oven, but do not have a source for used ovens, so if anyone has an article on modding current-ish model toaster ovens, I would really appreciate it. Tia!

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NemesisCTwistOneUp

Reply 1 year ago

Definitely I'm mostly very impatient and want instant melting -however not always a good idea! Yes having a low airflow helps a lot expecially when the component begins sliding around. Have you tried to use silly putty/tape to hold down the component? I've been told it works wonders

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christherock23

2 years ago

Awesome instructable! Personally i prefer the skillet method but this is mostly due to the fact that ive been doing it forever, i do all my PCBs 100% SMD. A cheap skillet on the stove sure beats trying to solder 50 components by hand lol.

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NemesisCchristherock23

Reply 2 years ago

Thank you Chris! Would you recommend any nice quality affordable skillets?

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christherock23NemesisC

Reply 2 years ago

To be honest just about any skillet will work. Im using an old one we had in the house (my mom burned chicken in it so she didnt want to cook with it anymore) the one im using has teflon which is great because the boards are easy to slide around. If you can find one at a thrift store that has a pretty good surface i would buy that and experiment with it. The hot plate method is great with parts containing a lot of plastic. Hot air tends to melt the plastic on things such as usb ports really easy. Hope this helps :)

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mdeudon

2 years ago

Good ;-)

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luckyluc

2 years ago

True, for this type of component it is not worth using this method.

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p_lericheNemesisC

Reply 2 years ago

Excellent Instructable - thank you NemesisC! But for only very occasional use the hot air solder station isn't easy to justify. I recently hand soldered a few SOIC-8 chips and a SOIC 20pin device to breakout boards. The key is to stick the boards to the bench with Blu-tac and rest your wrist on the bench to steady your hand, and use a sufficiently powerful magnifier, a 1mm iron bit and flux pen. Flushed with success I then threw caution to the winds and attempted 3 SSOP 8 pin devices, and succeeded! But it's quite tricky not to get solder bridges between the pads, though not too hard to clean them up with solder wick. I wrote it up at https://therestartproject.org/wiki/Surface_mount_soldering - take a look if you like.

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throbscottle

2 years ago

I tried this technique a few years ago using a heat gun and it was a disaster! The solder wouldn't melt whilst it seemed the chip was getting excessively hot.

However you have inspired me to try again. I'll try making longer pads like you have, maybe that is what makes the difference.

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diy_bloke

2 years ago

thanks for the write up. Would that be a hot air tool, or a hot hair tool (check the bold print under the top picture). For a moment I thought you'd be telling to use a blowdryer :-)

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NemesisCdiy_bloke

Reply 2 years ago

thank you for the catch! Added the fix :)

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HamishA1

2 years ago

are there better solder paste dispensers? it looked really slow and problematic with you dispensing the solder paste. anyone got some links to better ones?

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Eric BrouwerHamishA1

Reply 2 years ago

I use a Magnum MD100 dispencer. works great for me.

MD100.jpg
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NemesisCHamishA1

Reply 2 years ago

The reason why the GIF shows a shaky hand is because I was recording and applying the paste at the same time since I don't have a tripod. I kept checking if the shot was in frame to make sure people could see the process. I have only used the Chip Quik solder paste which comes with 2 different dispensers. Maybe Maker Paste would be useful it comes with a wider dispenser sold at Adafruit, Pimoroni and ICbreakout

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RaymondR6

2 years ago

This is a very useful guide, but why "a hot hair tool"? Even if it were a "hair dryer" the temperature will never reach the melting point of solder.

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cobusmalanRaymondR6

Reply 2 years ago

The hot air tool in question there is used for desoldering and soldering, it definitely reaches the correct temperature. I even use a normal heat gun in a very controlled fashion for the same purpose. You are right about a hairdryer though.