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AND STORAGE, TWO TIP CLEANERS, AND A SOLDER ROLL HOLDER.  DJI MINI
2, 4K VIDEO DRONE REVIEWED BY PASCAL VILLENEUVE VA2PV VA2PV ARRL.
ORG  YOURE PROBABLY WONDERING, WHY REVIEW A DRONE IN QST?  ASK
YOURSELF, IS A DRONE USEFUL TO AMATEUR RADIO?  HOW ABOUT FOR
INSPECTING ANTENNA/ TOWER INFRASTRUCTURE?  IF YOURE LIKE ME AND NOT
TOO MUCH OF A CLIMBER, THE ANSWER IS WELL, YES.  MANY OF YOU ALREADY
KNOW IM ALSO AN AMATEUR VIDEOGRAPHER, SO THERE WERE A FEW CRITERIA
THAT I WAS LOO THE IMPORTANCE OF CORRECT SOLDERING IRON TEMPERATURE
APPLYING THE CORRECT TEMPERATURE TO SOLDER JOINTS CAN MAKE THE
DIFFERENCE BETWEEN HAVING A SOLIDLY CONSTRUCTED PROJECT IN HAND OR A
DISASTER.  IN GENERAL, LEAD BASED SOLDER USUALLY CALLED 60/40
BECAUSE IT IS 60 TIN AND 40 LEAD REQUIRES A TIP TEMPERATURE OF 460
F, AND LEAD FREE SOLDER REQUIRES ABOUT 100 DEGREES HIGHER.  THE
COMPOSITION OF LEAD FREE SOLDER IS ROUGHLY 99 TIN, 0R7 COPPER, PLUS
VARIOUS TRACE METALS.  THE TEMPERATURE CONTROLLED SOLDERING IRONS IN
THIS REVIEW ARE CAPABLE OF PRODUCING TIP TEMPERATURES OVER 800 F, SO
PROPER TEMPERATURE ADJUSTMENT IS NEEDED.  THERE ARE TWO COMMON
PROBLEMS WITH INCORRECTLY CONTROLLED SOLDERING IRON TEMPERATURE.
FIRST, AS SEEN IN FIGURE E, AN INEXPENSIVE, POORLY MADE PRINTED
CIRCUIT BOARD PCB CAN LITERALLY BE BURNED AND ITS COPPER TRACES AND
PADS LIFTED UP OR EVEN DESTROYED.  THE BURN MARK SHOWN IN THE PHOTO
IS DUE PRIMARILY TO A POOR QUALITY PCB AND A TIP TEMPERATURE SET FOR
LEAD FREE SOLDER.  BEFORE WE LOOK AT THE OTHER COMMON PROBLEM, LETS
EXAMINE A GOOD SOLDER JOINT IN FIGURE F.  THOSE COLORS YOU SEE ARE
NOT ACTUALLY IN THE JOINT A GOOD SOLDER JOINT IS SHINY, SO WHAT YOU
SEE IN THE PHOTOGRAPH IS A REFLECTION OF THE MICROSCOPE AND
MICROSCOPE LIGHT USED TO CAPTURE THE PICTURE.  AT THE PROPER
TEMPERATURE, SOLDER WILL FLOW EASILY ON THE WIRES AND SURFACES AND
WILL ADHERE WELL WHEN IT COOLS.  BECAUSE COPPER DISSOLVES IN MELTED
TIN, THE SOLDER WILL FORM A THIN LAYER OF CU/SN ALLOY WHERE IT MEETS
WITH COPPER, FORMING AN EXCELLENT ELECTRICAL BOND.  FIGURE G IS
ANOTHER POOR JOINT, MADE WITH LEAD FREE SOLDER BUT WITH A 600 F TIP
TEMPERATURE THAT IS, FOR LEADED SOLDER.  THATS NOT QUITE HOT ENOUGH
FOR THE SOLDER TO FLOW AND ADHERE WELL.  IN A JOINT LIKE THIS, THERE
MAY BE ELECTRICAL CONTACT RIGHT AFTER CONSTRUCTION, BUT AFTER SOME
TIME THE CONTACT WILL BREAK A COLD SOLDER JOINT AND THIS DEFECT MAY
NOT BE VISUALLY OBVIOUS WHEN TROUBLESHOOTING THE PROBLEM.  EVEN
WORSE, THE JOINT MAY BECOME INTERMITTENT, MAKING IT EVEN HARDER TO
SPOT.  ITS ALSO IMPORTANT TO NOTE THAT SOLDER HAS VERY LITTLE
MECHANICAL STRENGTH AND WILL COLD FLOW IF IT IS STRESSED EVEN A
JOINT SOLDERED AT A PROPER TEMPERATURE CAN CRACK, COMPRESS, OR PULL
APART IF IT IS SUBJECTED TO MECHANICAL STRESS.  THEREFORE, IT IS
GOOD PRACTICE TO MAKE SURE COMPONENT LEADS, WIRES, ETC., ARE
SECURELY WRAPPED OR BENT OR OTHERWISE ANCHORED TO THE SURFACE THEY
WILL BE SOLDERED TO BEFORE THEY ARE SOLDERED.  THE PHOTOGRAPHS WERE
TAKEN WITH A KKMOON 600X DIGITAL
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