Building your own electronics is an incredibly rewarding experience. However, opening your new DIY FM Radio Kit and seeing tiny, surface-mount components can be intimidating. Unlike through-hole components with long legs that slip easily into pre-drilled holes, Surface Mount Devices (SMD) sit flush on top of the copper pads with no holes in the circuit board for insertion.
If you are working on the TNNJoy DIY FM Radio Kit (featuring the 16-pin 74HC595D Register chip at position U3 which has exactly 8 pins on each side), this step-by-step guide is for you. We will walk you through how to identify the correct orientation of your SMD chips and how to solder them with professional results, even if you are building this with your kids or grandkids!
Align the IC dot mark with the white notch on the PCB silkscreen before soldering.
Step 1: Alignment & Polarization (The Notch & Dot)
Unlike simple resistors, integrated circuits (ICs or chips) are polarized. This means they must face a specific direction. If you solder the chip backward, the circuit will short out and the chip may be permanently damaged.
Before heating up your soldering iron, examine your components closely:
The Chip Mark (The Dot): Look at your SOP-16 74HC595D chip (which has exactly 8 pins on each side). On one corner of the chip, you will find a small, circular printed dot (mark).
The Board Mark (The Notch/Gap): Look at the white silkscreen outline at position U3* on the purple PCB. You will notice a white gap (notch) printed on the right side of the rectangle outline.
The Match: Place the chip on the board so that the end of the chip with the dot* points toward the right, matching the white gap on the board.
Step 2: Choose one pad on the PCB at location U3 and melt a small amount of solder on it.
Step 2: Tinning a Single Pad
Once the chip is aligned, it is time to prepare the board. Since the chip has no pins going through the board, you cannot flip the board over. Instead, we use the “Tack and Flow” method.
Choose a single corner pad on the PCB.
* Apply your soldering iron tip to that pad, and melt a tiny amount of solder on it to create a small mound of solder.
* Keep the other 15 pads clean.
Step 3: Melt the pre-tinned pad with the iron while holding the IC in place with tweezers to secure the chip.
Step 3: Tack and Position the Chip
Using a pair of tweezers, pick up the chip. Align all 16 pins (8 pins on each side) with the copper pads, ensuring the dot is pointing to the right.
Use a soldering iron to melt the tin on the pad you just prepared in Step 2.
* Hold the IC firmly with tweezers in the other hand to place and press the chip onto the U3 footprint, preventing any movement.
* Take care to match and align each of the 16 pins to their respective copper pads.
* Once aligned, remove the soldering iron.
* Wait for the solder to cool and solidify, then remove the tweezers. The chip is now anchored!
Step 4: Solder the remaining pins and use a desoldering braid or solder sucker to clean up any solder bridges.
Step 4: Solder Remaining Pins and Clean Up
Double-check that all pins are still perfectly aligned with the pads. If they are, you can now solder the remaining 15 pins.
Connect the other pads on the 74HC595D to the PCB pads using tin and a soldering iron.
* Pro Tip for Drag Soldering: You can use a slightly larger amount of solder tin to cover all the pads, ensuring all pins and pads are covered.
* While keeping the tin in a melting state with your soldering iron, use a solder sucker or desoldering braid to remove any excess solder. This ensures each pin has a clean, independent joint without bridges.
Success! A fully assembled FM radio ready to play your favorite local stations.
Working on electronics projects is a fantastic way to develop critical thinking, patience, and fine motor skills. It makes a wonderful weekend project for hobbyists and a memorable bonding activity for grandparents and grandchildren.
At TNNJoy, we believe in smooth, successful builds. That is why:
California Warehouse: We stock and ship all kits directly from our California warehouse, guaranteeing fast 3-to-5-day delivery to your doorstep.
* Comprehensive Guides: All our kits come with clear, digital assembly manuals and lifetime customer support.
If you are ready to tackle your next DIY electronics project and build your own fully functioning FM Radio, you can get our complete kit directly on our store:
👉 [Shop the TNNJoy DIY FM Radio Kit on Etsy]