Omron B3K series
- See also
B3K is a series of keyboard switches manufactured by Omron, and originally designed in partnership with Logitech and designated “Romer-G™”. The series is notable for being seemingly the first modern (as in, following the general demise of high-end consumer keyboards) computer keyboard switch to be introduced that is not based on an existing switch type (e.g. Cherry MX or Alps/Forward SKBL/SKBM). Romer-G is a significant redesign of mechanical switching, providing a central light pipe for optimal keycap legend illumination and redundant switch contacts.
Logitech Romer-G was introduced in 2014 and is covered by US patent 20150043192 “Switch and keyboard provided therewith” filed in July 2014 by Omron. These switches bear the Logitech “G” logo on the front and the back, and a small “OMRON” logo on each side. A second variety followed in 2016, the Das Keyboard Gamma Zulu, which features Metadot’s stylised “D” for Das Keyboard. Omron also manufacture Creative’s PRES (Perceive-React-Execute Switches), which seemingly do not feature any custom branding. Several types (B3K-T13L, “B3K-T13L2 BY OMZ” and B3K-T135M) are listed on the Arrow website, but they are not orderable. Anglia Components list B3K-T135L, B3K-135C, B3K-T135 and B3K-T135C, all of which may be ordered, price on application. Omron Product Code Change AMP-Z-2007029 depicts two models, B3K-L135 and B3K-T135-L, with the Omron logo where the customer-specific branding should be (just as with the Creative PRES model of B3K-T135, also listed but not depicted), implying that these are generic models available to any customer. The recess for the customer logo is absent from those models.
B3K is confirmed to have been manufactured in Japan; Linus Tech Tips took a tour of the B3K production line in 2015. However, Omron Product Code Change AMP-Z-2007029 seems to indicate that production of at least some models moved to China as of October 2020. This notice implies that lot numbers in the form nnnnRn indicate Japan as the country of origin, while nnnnCn denotes Chinese-made parts. Original Romer-G switches obtained from AliExpress in 2015 all came from a lot of type “C”, while B3K-L13L bought in 2018 used both “R” and “C” codes. B3K-T13L-L switches also from 2018 came from a variety of both “C” and “R” lots, while all the B3K-T13L2 switches received were from “C” lots. There is thus a tentative suggestion that there are (or were) separate production lines in Japan and China. Omron themselves have refused to comment on this or any other aspect of keyswitch manufacturing, past or present (even though two factory visits have been made to date, in 2015 and 2019, by Linus Tech Tips and HardwareCanucks respectively).
Despite being a dedicated design, the Romer-G switches have not been as well received as it should have been. In particular, the tactile feedback of the original design fairly indistinct. The damping was removed with later models, as that too seems to not have been sufficiently appreciated. The later undamped tactile versions have a distinctly higher level of tactility, although still less than Cherry MX Brown. No versions presently provide audible feedback.
B3KL series follows B3K and reduces the switch design to a much smaller size, and adds the missing click feedback. Hardware Canucks reported, from their tour of the Omron B3KL production, that re-engineering B3K to offer click feedback would be difficult and expensive, which is why B3KL was designed from the outset to be a click type, such that the click feedback can simply be removed for customers who would prefer not to have it.
B3K switches have a very soft tactile response, significantly less than force curves would suggest. In fact, the official force curves presented by Logitech, Metadot and Creative are all a mess. The Creative PRES graph appears to be an old 3.0 mm travel graph with the full travel position relabelled as 3.5 mm. The Logitech 3.2 mm travel graphs do not correspond with each other. The Metadot graph is also wrong. The diagram below shows all four graphs scaled such that the manufacturer’s defined operating point appears at 45 gf and the end of travel appears in the correct place at 3.2 or 3.5 mm accordingly. The 1.5 mm operating points are shown with vertical lines to show how far out all of them are. The graphs could also be scaled such that all the 1.5 mm operating points are in the right place; this results in a variety of wrong travel distances and less correlation in the tactile peaks. This diagram shows however that, by and large, all the tactile versions are specified largely the same. The fact that B3K-T13L2 is noticeably more tactile than B3K-T13L is not covered by these graphs.
Extensive testing of B3K switches can be found in the Tom’s Hardware Logitech G810 Orion Spectrum review in May 2017, including stabilised and non-stabilised keys and the tolerance range of the switches. The number of outlier switches in their example is quite surprising.
B3K switches are stamped with their part number and lot number. Romer-G switches are widely available to buy through AliExpress and Taobao, allowing these codes to be observed; this is sadly not true of Creative PRES and Das Keyboard Gamma Zulu. Although no official documentation is known for the part numbers, examination of Romer-G switches allowed for part of the schema to be tentatively decoded. José Soltren of Metadot has provided photos of Gamma Zulu; the second “L” in Romer-G part numbers was suspected to stand for “Logitech”, implying that Gamma Zulu would have “M” for Metadot in this position, and this turned out to be the case. Creative refused to provide any information relating to the part numbers of their PRES switches.
The part number schema below is a previous interpretation based on the examples discovered up to that point. Further part numbers obtained since indicate that the part numbers are more complicated.
The individual positions are suggested to denote the following:
- Omron B3K series; the derivation of this is not known, but B may denote pushbutton (reed and Hall types fall under B2x and mechanical types under B3x)
- Switch type: T: tactile, L: linear
- Unknown; this could denote momentary
- Travel: 3: 3–3.2 mm, 35: 3.5 mm
- Customer: L: Logitech, M: Metadot, C: unknown
- Possibly Romer G 2.0 (a designation found on the Arrow website for B3K-T13L2)
- Unknown; only known from a model with no light guide
The explanation of “3” and “35” (or indeed “13” and “135”) remains a guess. As of 2020, the Logitech website gives 3.2 mm as the travel distance for Romer-G switches, while originally travel was given as 3 mm. No Romer-G switches have the travel distance claimed, which makes verification difficult, but broadly it does appear that the original blue types (B3K-T13L) have less travel than the later models. One explanation could be that the removal of the damping prongs increased travel slightly, and the code remained “3” as the change in travel was not intentional and the rest of the switch remained unaltered.
The following models are known, either from inspection of switches or from Omron Product Code Change AMP-Z-2007029. For the Romer-G variants, the total travel listed is the measured amount instead of the official amount, as the official figures appear to be off by around 0.2 mm.
|black blue clear
|black black clear
|Salvaged from a Logitech G413; there is no light guide present, even though the G413 is a backlit model
|Mk II switch, with the damping prongs removed from the mould; factory lubricated
|Received in the same order from China as B3K-T13L2, and the two types appear to be identical otherwise
|black black grey
|Linear version, also without the damping prongs; factory lubricated
|black black grey
|Listed in Omron Product Code Change AMP-Z-2007029; Creative PRES seems to be a generic B3K-T135 model.
|black black clear
|white transparent clear
|Das Keyboard Gamma Zulu
|black black clear
This is the original Logitech Romer-G™ model, which can now be distinguished by its bright blue colour. This model provided damping prongs, a characteristic that appears to have been found undesirable, as no models since have included them. Damping prongs are not a new idea, as Clare low-profile reed used a similar design.
B3K-L13L is a linear Romer-G switch. The cover of the shell is black, a colour choice that would become standard with all models until the Creative PRES. The damping prongs have been removed from this model. Parts of the prongs can still be found on the plunger, suggesting that maybe the moulds were modified afterwards, and that this switch would have been damped if the original design had remained.
Tom’s Hardware article Romer-G Goes Linear: Logitech’s Latest Mechanical Keyboard Switches from March 2018 gives a rough idea of when this switch type was introduced.
B3K-T13L2 is another Romer-G type. The “2” suffix to the part number implies “Mk II”, and on the Arrow website the B3K-T13L2 entry notes the following:
Switch, Push Button, SPST, 15.6x15.6x14.5, 46+/-20G, 70M, 3.2+/-0.2, Romer G 2.0
Just as with the linear Romer-G switch, this model is undamped. This model is factory lubricated.
This model was found in a Logitech G413 keyboard. While this keyboard is indeed backlit, there is no light guide in this switch model. Some keycaps include front legends in addition to top legends, and possibly this is the reason why the light guide was removed. The following photos were provided by Андрей Студенцов (chromov113) and are public domain:
This is a Das Keyboard–branded version for Metadot, named “Gamma Zulu” (no less cryptic a name than “Romer-G”, being unsure of whether it wants to use the NATO spelling alphabet or the Greek alphabet). See Omron Gamma Zulu Switch Study for photographs of this model. This is a lubricated tactile model.
There is no observable difference between B3K-T13L-L and B3K-T13L2. Both are undamped tactile Romer-G switches. Both types were shipped out together by a Taobao seller who also seemed to believe they were the same switch. Although L2 turned up earlier, there is no definitive proof that either model was produced before the other.
B3K-T135 is a curious model. There is no suffix to the part number, suggesting that it has no branding other than Omron’s, which is indeed the case. Although all B3K switches bear Omron branding, this model has larger and more prominent Omron branding in a location where the customer-specific branding is otherwise placed. The example depicted below is from a Creative SoundBlasterX Vanguard K08 keyboard, making it a Creative PRES type. The shell cover is transparent, which seems to be related to the backlighting process. This clear plastic of the cover is brittle, and if the cover should break while attempting to repair a failed switch, it cannot be substituted by that of another B3K model, as all the types sold in China are Romer-G types and those have opaque covers.
The following photos were provided by Андрей Студенцов (chromov113) and are public domain:
The black substance seen on the switch contacts interferes with switch operation and appears to be at least a partial insulator. Андрей noted that, after removing it with a dremel, the switches work correctly again.
- Omron Product Code Change AMP-Z-2007029, 2020-08-17, covering the move from Japanese to Chinese manufacturing, and listing four seemingly generic models (B3K-L135, B3K-T135-L, B3K-T135 and B3K-T135C)