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Practical Electronics Editorial offices Electron Publishing Tel +61 2 9939 3295 (Australia) Email pe<at>pemag.au Web www.electronpublishing.com Address mail to: Electron Publishing (Australia) PO Box 194, Matraville NSW 2036 Australia Advertising enquiries +61 2 9939 3295 pe<at>pemag.au Editor Nicholas Vinen Publisher Nicholas Vinen Digital subscriptions Stewart Kearn Tel 07918 614662 Online Editor Alan Winstanley Web Systems Kris Thain Production Bao Smith Technical staff Tim Blythman, John Clarke Print subscriptions Practical Electronics Subscriptions PO Box 6337 Bournemouth BH1 9EH Tel 01202 087631 United Kingdom Email pesubs<at>selectps.com Technical enquiries We regret that technical enquiries cannot be answered over the telephone. We are unable to offer any advice on the use, purchase, repair or modification of commercial equipment or the incorporation or modification of designs published in the magazine. 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The laws vary from country to country; readers should check local laws. 2 Volume 54. No. 10 October 2025 ISSN 2632 573X Editorial Are surface-mount devices less reliable than through-hole? This month, I became aware of the idea that some people think that electronic devices populated with surface-mount devices (SMDs) are somehow less reliable than those made with the older-style throughhole parts. My first thought was to question why the packaging method of a device affects its reliability. For example, the good old TO-92 package BC546 is available in an SOT-23 SMD package, as the BC846. It has a lower dissipation rating of 310mW compared to 625mW, due to its smaller size, but the internals are identical. Other than failing to take that lower dissipation rating into account (which would be a design flaw, not a fault of the part), is there any reason to believe that a BC846 should not last as long as a BC546? In fact, SMDs were developed in the 1960s primarily for military and aerospace applications specifically because they were more reliable (and also more compact, which obviously helps when you’re trying to fit electronics in a rocket or aircraft). That’s because lead flex means that a component body on the end of leads will tend to move around in response to vibration and shocks. That stresses both the leads and the solder joints, risking eventual failure. That doesn’t mean SMDs are always better; they are more sensitive to board flex, for example. But in general, they are thought to be more reliable, are cheaper to make, take up less space, offer better RF performance due to the smaller size and so on. Of course, being smaller means you need better eyesight to see and work with them (unless you’re using a microscope), steadier hands and finer tools. The myth of SMDs being unreliable likely persists because poorlyengineered budget devices use them – not because the parts themselves are inherently inferior. When cheap gear fails, people open it up and see SMDs inside, and assume a causal link. When it comes to repairing devices, there are actually significant advantages to SMDs. Yes, you need more skill to work on them, but you can remove and reinstall them with access to just one side of the board. It’s also possible to ruin multi-layer boards with plated through-holes when removing through-hole parts (and it’s frustratingly difficult, too). Ultimately, the biggest obstacle to repair these days is lack of documentation or replacement parts, not the difficulty of replacing the failed components once you’ve identified them. I understand why people might not like to work with small, fiddly parts but they are not inherently any less reliable. Nicholas Vinen, Electron Publishing (Australia)* Publisher & Editor, Practical Electronics Magazine * a division of Silicon Chip Publications Pty Ltd. Practical Electronics | October | 2025