You could cover your ears when someone trills on the last hole with a wind instrument, because these are the highest notes that the instrument can produce and they often sound extremely shrill. Since the musician can't tickle any higher notes out of the instrument, he has to give up if the score demands even higher ones. This leads us on a musical detour to through-hole technology (THT).
The Japanese poet and ultra-nationalist Yukio Mishima in Tokyo before he committed seppuku - the last Japanese to do so (1970). Seppuku is a ritualized form of male suicide practiced by the Japanese samurai, in which a suicidal man determined to restore his honor cuts open his stomach with a dagger or sword - inflicting the ultimate last hole, so to speak.years ago, when the first surface-soldered components appeared on assemblies, several experts were already predicting the end of through-hole technology (THT): It was whistling on the last little hole, so to speak, because it needs holes after all, but these are usually referred to as 'through-hole platings', except in the case of single-sided laminated PCBs. This was the case in the 1960s when SM (surface mount) was originally called 'planar mounting' and was once again first used by IBM in a small computer.
However, this predicted hara-kiri (腹切) - the term goes back to Christian missionaries in Japan - of THT is somewhat premature and unfortunately the self-appointed augurs did not then commit seppuku (切腹) as befits proper samurai who have lost face. It can therefore be assumed that further dubious predictions will be launched by them in the relevant press.
Although SM technology has a number of seductive advantages, THT continues to enjoy astonishing popularity, because SM also has disadvantages and THT has advantages.
A quick look at market shares shows just how well leaded components are doing: the global market size for leaded components reached $41.1 billion in 2024. The IMARC Group expects the market to grow to $67.5 billion by 2033. [*]
In contrast, SM technology, at $5.73 billion in 2023, will have to stand on its toes to be noticed. Once again, it seems that the 'dead live longer'.
There are, of course, reasons for this, which were already discussed when the first SM components were introduced: Do the soldered connections on surface-mounted components last as long as those of the wired ones in their holes?
It was found that the quality was sufficient in many respects, but if there was too much wobbling (vibrations), if they were subjected to repeated mechanical stress (mechanical shock) or if they had to undergo many 'dramatic' thermal excursions, they were better off with wired components. As a result, these components have secured several very important areas of application.
The drive towards ever smaller components in order to reduce device sizes to such an extent that 'cell phones' can be handed to small children is backfiring in a way. Tiny components such as the 01005 components, which are currently causing a sensation, can hardly be placed on the solder paste with shaky fingers. Applying paste to the landing surfaces and then placing the component so that the many possible errors are reliably avoided requires expensive machines, which a small, struggling company cannot afford. Consequently, this is left to large companies that can also hire personnel to tackle the problems that arise here [1]. For all those who have plenty of space in their (household?) appliances, this step is therefore not worthwhile.
Since through-hole technology has been around for over fifty years, the various process steps are familiar to most companies. Assessing the quality of vias, threading components by hand (still widespread!) or with machines and robots, then wave soldering and testing everything is largely routine and is carried out in many smaller companies by housewives who have pictures of their grandchildren on the table.
The PiP (pin in paste) approach is somewhat more exotic, utilizing the reflow process that the assembly has to go through anyway because the majority of the components have been placed on the surface (mixed assembly). Two main questions arise here: a) how do you get enough paste into the holes and b) how can you avoid the paste being pushed through during placement and thus being lost?
Pin-in-paste method
The calculation of the paste quantity depends very much on the specification of the through-hole plating and the shape of the connecting wires - round or flat, rectangular or square? Luckily, there are some math geniuses who provide the user with the appropriate formulas, which are at least necessary for the calculation.
Pushing the paste through depends on the threading speed and even more on the consistency of the selected paste. Rounded or pointed legs may have fewer problems than those with flat ends. In addition, it should not wobble during transportation, nor should a bumpy transfer from one conveyor belt to the next cause the often tall components to tip over.
Which automatically brings us to the idea of repair. With the 01005 components, repair is regularly largely ruled out, especially if it is to be carried out by hand, as is traditionally the case. The internet is full of good advice, but large-scale production tends to focus on achieving low error rates. With wired components, you can't just use a hot soldering iron to eliminate the fault, there is a wide range of equipment that can help. In addition, wired components are more suited to human size than the smallest components in the SM category.
People forget that the now popular selective soldering systems have evolved from repair machines. Instead of PiP, the solder joints remaining after reflow soldering can often be produced with such devices in mixed assemblies. However, the ten or twenty selective soldering machines at the end of some production lines indicate that the design of the assembly leaves a lot to be desired. The managers and designers should perhaps take a course in DfM (Design for Manufacturing), because although this would hurt the poor machine manufacturers, it would dramatically reduce costs and especially error rates.
This does not mean that PCB manufacturers have to get rid of their great drilling machines, because holes in PCBs will certainly continue to exist for a long time to come. Whether additional holes should be drilled in blowing instruments is a moot point.
Passive components of the 0603, 0201 and 01005 series
Paste pushed through
References
[*] www.imarcgroup.com/through-hole-passive-components-market (Retrieved: 16.06.2025).
[**] Yu Wang, Michael Olorunyomi, Martin Dahlberg, Zoran Djurovic, Johan Anderson and Johan Liu, 'Process and pad design optimization for 01005 passive component surface mount assembly', Soldering & Surface Mount Technology Volume 19, No. 1, 2007, p. 35 (Retrieved: 16.06.2025).
Literature
[1] Sjef van Gastel and Claudia Mallok; '01005-SMD-Chips verarbeiten Bei einem Abstand von 60 µm sind 01005-Komponenten produktionsgeeignet'; Elektronik Praxis; 2009.
[2] Vatsal Shah et al; Process Development for 01005 Lead-Free Passive Assembly: Stencil Printing; Speedline and Indium Corp 2006.
[3] Vamsi Gajula; 'How to solder components on PCB by using through hole reflow process; 33 digital we days'; April 23, 2024.
[4] Ross B. Berntson et al; 'Through-Hole Assembly Options for Mixed Technology Boards'; IPC Printed Circuits Expo; SMEMA Council APEX ; Designers Summit 04.
