I use an adjustable temp soldering iron, which came from the factory with a brass tip scrubber. I find it amazing for cleaning soldering tips. One stab into the brass shavings,
is all it takes to clean the tip.
- Pinching between the two wires as shown, ensures the glue closes off to a perfect moisture seal around the two wires in question.
Male Swiss machine pin headers are much kinder to solderless breadboards than their square pin cousins.
Micro Soldering Technique for SMDs
Assumptions:
- Solder paste will not be used.
- Using a Hakko FX888D soldering iron.
- Consumables, liquid flux, 63/37 0.025” diameter solder, de-soldering braid.
- SMD component will be similar to SOT-23-6 or SOT-353-6
Below is a discussion for small form factor SMD component lead soldering.
- Flatten 1” of .025” solder with smooth jawed Knipex pliers.
The flattened solder allows you to add a very small amount of solder to the iron’s tip. - Add a small amount of liquid flux to the 1” flattened solder.
- Clean the PCB pads with a no lint tissue soaked in IPA.
- A magnetic hold-down clamp keeps the SMD in place on the PCB pads while it is being soldered.
- Brush a small amount of liquid flux on the SMD leads/pads.
- The best iron tip for small component soldering is the curved Hakko T18-BR02.
- If you have old eyes, a soldering stereo microscope does make this job easier.
- From here on in, work quickly to avoid solder oxidation.
- Using a moist sponge, clean off all solder from the soldering iron tip.
- Slightly touch the end of the iron’s tip with the fluxed, flattened solder.
We are aiming for a micro amount of solder at the very end of the tip.
If you notice too much solder on the tip, clean it again on the sponge, reapply solder. - During component lead soldering, we normally do not add solder to an iron’s tip, however, in this technique, we do.
- Quickly and lightly touch the component lead with the melted solder you just added to the tip.
The flux you added to the component pads/leads should yield shiny finished soldering results. - Too much solder on a component lead can be removed with fluxed thin de-soldering braid.
- After all component leads are soldered, clean off soldering flux residue with IPA; an old electric toothbrush works great.
Use Single or Dual Logic Gates in Your Projects
With reference to Post #975 and the Link below:
Selection Tables
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Very often, we need only one or two logic gates to make our circuits work.
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We can avoid the larger versions of these I.C.s by using small SMD single/dual logic gates.
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SOT23-5/6 and SOT-353-5/6 form factors are available and can still be managed with manual soldering, as seen in the previous post.
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Below are gates I often use.
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Many other logic families and gates are available.
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These gates are inexpensive, ex. 50PCS SN74LVC1G66 about $2.00
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Suggest you look at the SN74LVC version of these chips as their Vcc can be 1.65V to 5.5V
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The inputs of the LVC family are 5V tolerant.
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LVC can be used as 5V to 3V3 logic level shifter. i.e. 5V logic --> 3.3V.
As a side note, we can use theSN74AHC1G125SN74AHCT1G125 for 3V3 to 5V.
Linear
- LMV321 Single supply OP Amp
and - TL331 Comparator
Circuit Example
- We need a Schmitt trigger connected to a switch:
You might want to consider using these small, inexpensive gates in your projects.
Lets Protect Our Arduino From Us
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This has been covered a few times. The following will show how we can save our Arduino from ourselves.
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There are quite a few new Arduino users that damage their Arduinos by accidentally shorting output GPIO pins.
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Suggest new users (and some of us oldsters too) use the following technique to prevent output GPIOs Arduino pin damage.
Edit
Pin Vises
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Sometimes the simplest tool can make a job so much easier.
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Pin Vises are just one of these tools.
This vise can grip things like: shafts, drill bits, files, countersinks and much more. -
Hobby Pin Vises are inexpensive and can be found almost everywhere.
Cost is about $5.00 to $15.00. -
If aluminum, make sure the aluminum thread on very inexpensive vises fit the chuck well, if too sloppy, the thread will strip.
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The Pin Vise is great when using the Nut & Screw starters made in Post #1216
Tweezers #1
Building an SMD Turning Plate.
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If you have ever done SMD Soldering, you know how frustrating it can be to upright SMD components.
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SMD resistors, LEDs, Transistors, and I.C.s all seem to be upside down when you dump them out on a surface.
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We can make the job of up righting these components easy by using the Turning Plate described in the images below.
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The key element of this tool is the High Friction silicone surface on an aluminum plate.
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Add a grasping, M2 brass standoff, post to let you easily pick up the tool with your fingers.
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The silicone material used here has adhesive backing that is stuck to the .064” aluminum.
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Alternatively, you can use a piece of silicone cookie sheet.
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Sharp tweezers are used to apply pressure to the component side edge, closest to the tweezers.
Pull/slide the tweezers toward your hand as seen in the attached YouTube video.
Tweezers #2
Add a Double Stick Tape Plate and a Mini Turning Plate to our toolbox
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Below is a discussion how we can use our new SMD tools to make two ESP32 PCBs.
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We saw in the previous post how to make an SMD Turning Plate
We can make a similar plate tool, but this time add Double Stick Tape to its surface.
To make the tape less sticky, denature by touching the surface with your fingers.
This new plate is used to hold the SMD components needed to make a PCB. -
Using the same idea as the Turning Plate we make a Mini Turning Plate.
The mini plate is held with a Magnetic Pinch Clamp on our work surface.
We use this Mini Turning Plate if you accidently overturn a component.
Magnetic Hold Down Clamp Soldering Method part 1
Soldering Method Explained
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I was asked to elaborate on soldering SMDs using the Magnetic Hold Down Clamp.
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The attached images and YouTube video should be self explanatory.
Magnetic Hold Down Clamp Soldering Method part 2
Make a Fulcrum Assembly to lift the Clamping Arm
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At its simplest, the Clamping Arm can be lifted with your thumb and index finger.
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If you use a simple Fulcrum Assembly, you will find the soldering process goes a lot faster and the process is easier on your wrist.
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Suggest you make an ABS plastic assembly as seen in the images, however, I have used a wooden version for years.
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See the attached images to see how the Fulcrum Assembly is used.
See the YouTube video in the previous post.
EDIT
See Post #1255
Ultrasonic Cleaning of PCBs
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If you have access to an Ultrasonic Cleaner, use it to remove all flux residue from your finished PCBs. (follow the ultrasonic cleaner directions)
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3L Ultrasonic Cleaning Machines cost about $90.00 to $120.00.
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A clean PCB is a must for you to double check all your solder connections.
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I use ~500ml of 50-75% IPA in a Ziploc bag, insert into the machine’s water bath.
This reduces the amount of solution needed, it can be recovered and used multiple times. -
Follow the warnings in your ultrasonic machine user manual.
Do not use flammable liquids as this can be a fire hazard ! -
The water bath is about 50 degrees Celsius; the machine is filled two thirds full.
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Eight minutes is sufficient for cleaning flux from PCBs.
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After cleaning, rinse the PCBs in warm water and blow dry.
Note:
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Components like: switches, potentiometers, motors, unsealed relays, etc. should be soldered onto the PCB after the ultrasonic cleaning process.
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For components like sensors speakers etc. read the data sheet to see if there are issues if they are placed into an ultrasonic cleaner.
Is there a caution about including switches and connectors on the PCB?
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The Note is in the discussion above.
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My rule is not to place the components mentioned above into the cleaning solution.
We can imagine residual flux can settle in these parts making them intermittent or might damage the internals.
For example, let’s say a potentiometer had cleaning solution get into the wiper assembly.
Small amounts of flux might contaminate its workings.
The same would go for some relays, motors, sensors, and similar. -
Also, components that are lubricated would have their lubrication removed.
Hand Soldering an ESP32 Wroom-32 MCU Module to a PCB
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New users who have not done a lot of soldering might find this method of castellated SMD soldering interesting.
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Solder paste is best used for this kind of application.
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For hand soldering, I keep normal soldering iron tip temperature at 350 degrees Celsius.
In this procedure, raise the tip temperature to 400 degrees. -
We first solder each castellation as see in the attached YouTube video.
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After soldering each cove, add a small amount of good quality solder flux paste to the string of pads.
Used here is MG Chemicals 8341
Drag solder all the pads as seen in the video. -
After soldering, using an electric toothbrush, clean the pads with IPA.
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Do a close visual inspection to make sure all connections are quality, see attached images.
Very nice!
What is the material cooling/drying behind the pads in the last few seconds of the video?
- That's IPA (Isopropyl Alcohol) vaporizing.
Ah. Thanks!
Tweezers #3
Tweezers, Must have Electronic Tools
Some of the following points will be obvious, however, they need to be emphasized.
New people to the electronics hobby might find the following discussion useful when selecting tweezers to buy.
What to get:
- Reasonable precision-made tweezers can be purchased for $10.00 to $15.00.
I use the following 3 tweezers most often.
MaAnt SS-J @ $7.50
MECHANIC KA-11 @$8.30
MECHANIC Aac14 @$7.00 - I purchased the above tweezers through AliExpress:
- Look for high quality Stainless Steel or Titanium construction.
We use tweezer lengths between 11cm to 16cm in electronics. - Ceramic tweezers are great for sliding solder wick when desoldering, add solder flux paste to the wick to greatly increase its effectiveness.
Ceramic tweezers can withstand very high temperatures.
These tweezers can be fragile, avoid dropping. - Non-magnetic tweezers are a must as very light SMDs might be ferro magnetic.
You might want a set of magnetic tweezers if they are to be supported by a magnet. - I prefer non-serrated tweezers.
However, serrated tips help in grasping items (ex: soft wire insulation, cleaning wipes). - Tweezers tips can be bent inward to make them Rat Tooth tips.
This helps to prevent slippage on things like wires and when removing I.C.s etc. - Sharp tweezers allow you to pick up smaller dimensioned components like 0402 or 0603.
- Tweezers with holes in the arms provide a non-slip grip.
Polished arms might slip in your fingers. - Suggest you have 3 types of tweezers: precision tip, rough and tumble, and wide spade.
- Consider having a set of reverse (self-closing) tweezers.
Self-closing tweezers are highly effective in soldering male headers to a PCB. - In the event your working tweezers get damaged, buy a second set of tweezers to have on hand.
Suggestions:
- Close the tweezers on components lightly.
Only use enough pressure to grasp and manipulate the SMDs you are positioning.
Only use enough pressure . . ., this deserves repeating.
Let the tweezer’s resistance feedback tell you if enough pressure is being applied.
If the tips of your precision tweezers bend when you pick up SMDs, you are using too much closing force on the arms.
Too much pressure can launch the SMD across the room.
Too much pressure on an object can bend the tweezer’s tips. - To prevent dropped components from landing on the floor, work towards the center of your workbench.
- Curved Tweezers are great for reaching over other components on your PCB.
- Experiment/practice in grasping curved tweezers to achieve 45° 60° and 90° component grasping (see images below).
Do not overlook your grip on the tweezers; it can make a world of difference in comfort and in the ease of accurate component placement.
Curved Tweezers can be used perpendicular or parallel to the work surface. - A rubber “O” ring can be added to normal tweezers to keep them closed on SMDs.
- Add stripped silicone wire insulation to tweezer tips for extra friction and to keep the metal tips from touching components.
Also gives tip protection when the tweezers are not being used. - Wear an antistatic wrist strap when manipulating static sensitive components with tweezers.
- When soldering, make sure tweezer tips do not extend below your SMD component.
If they do, you might be soldering the component above the PCB, i.e., not flush to the PCB.
After soldering one lead of the SMD, apply slight pressure to the center of the SMD component with closed tweezer tips. Remelt the solder on that same SMD lead.
Alternatively, position the SMD with the tweezers, use a magnetic hold down clamp to keep the SMD in place while soldering, see previous YouTube video. - To keep tweezer tips from sticking to components, use IPA routinely to clean soldering flux from tips.
- If necessary, you can tune tweezer tip surfaces with folded fine grit sandpaper.
Rules of use:
- Do not use your precision tip tweezers for picking up larger, heavier objects.
Avoid using them with hardware like screws etc. - Never pry with your precision tip tweezers.
- Keep tweezer tips away from flames as the precision tips can be damaged.
- Avoid using your precision tip tweezers to scratch surfaces.
Use a dental pick instead. - When not in use, store your tweezers in a safe protected location.
When not in use, protect tweezers tips with silicone, surgical or plastic tubing.