0 Ohm resistors

[gxti]

I would think it would be cheaper to use the jumper wires they use in that picture rather then 0 ohm resistors.

You're right, jumpers should cost less than jumpers with ceramic on them. It's possible that some machines can't handle bare jumpers, but if yours can then I've got no clue. You'll have to ask whomever is giving you these designs.

Sort of funny how many people in this thread keep offering the same explanation about SMD pick-and-place because they aren't reading...

[tnt]

Is it easy to find jumpers on reels ?

[metalphreak]

If anyone has ever seen the Atmel ButterFly developement boards, mine came with what was essentially a COM Port socket, with a 3pin header and some 0 Ohm resistors to connect to the board. Only thing I can think of, is that it stops solder from flowing from one side to the other, especially when the axial leads are cut short. It also provides some insulation, if the jumper is going across exposed tracks or other components.

[madmaxbryan]

Yes, you can find 0 ohm through hole resistors on a tape reel. any axial sequencer and inserter will cut and bend then the same way they would a regular resistor, it doesnt know the difference. if you take a 0 ohm through hole resistor and smash the ceramic off, you will see that its just a straight piece of wire (jumper wire) with the ceramic around it, theres really no resistance other then what little bit the wire itself might have.

[tekfan]

My guess is the 0 Ohm resistor manufacturers are just covering themselves for the worst case scenario. In real life, they're most likely to be much less than 0 Ohm. 10m Ohm resistors are also normally surface mount and physically larger than some 0 Ohm resistors.

Neat! Cheapo two-wire amplifiers, no need to order tunnel diodes anymore 

Are tunnel diodes really unobtainable? I can't seem to find anyone that sells them. Can't even find the once popular 1N37xx series!

[Neilm]

The main reason for 0 ohm links is to give the designer some flexibilty on the board.

 If a designer thinks that a resistor might have to go there when the board is tested then the 0 ohm link puts pads where he wants. It can also be used to bypass bits of circuit. For example I have designed a widget that comes in several flavours. If you don't want all the bells - then the circuit is bypassed by fiting the link (and money is saved by not fitting the components. Alternativly, if you want the bell the 0 ohm link is not fitted and the other circuitry is. This will allow a designer to increase the volumes on the PCB and reduce the cost.

Yours

Neil

[Wim_L]

Are tunnel diodes really unobtainable? I can't seem to find anyone that sells them. Can't even find the once popular 1N37xx series!

I do think they're still around, but have mostly been replaced by fast IC amplifiers which are somewhat less tricky to use. There are also Gunn diodes which have similar characteristics, but they also seem unavailable through the usual big names. I suppose they're specialty devices mostly used by those with special high frequency needs.

[ArtemisGoldfish]

Just for kicks, http://farm6.static.flickr.com/5302/5614765792_bac140e704_b.jpg Here's a picture of a board with quite a few 0 Ohm resistors.

[tekfan]

Just for kicks, http://farm6.static.flickr.com/5302/5614765792_bac140e704_b.jpg Here's a picture of a board with quite a few 0 Ohm resistors.

Wow. That's some very high frequency design right there. You can see that the 0 ohm resistors are used as jumpers to go above the ground planes. Maybe they're even used as extremely low value capacitors. It doesn't take much capacitance to make a big difference in a >10GHz circuit like this.

[Zad]

Just for kicks, http://farm6.static.flickr.com/5302/5614765792_bac140e704_b.jpg Here's a picture of a board with quite a few 0 Ohm resistors.

As someone who does RF work, can I just say that board is pure pornographic FILTH!

 

[House91320]

how would a zero ohm resistor be possible

[Joshua]

In Dave's latest review of the hot air rework station (Atten?), On the pcb, you can see some 0 ohm resistors.

Joshua

[ciccio]

Well, through-hole 0 ohm resistors are simply jumper wires with a plastic (or ceramic)  coating in the middle.
They are available in reel form, and can be prepared (bent and cut) and eventually inserted in the PCB with the same tools that are used for standard resistors.
They were available also as simple pieces of wire, without the "resistor like" body, taped in reels.
Many years ago I've seen a machine that, starting from a spool of solid wire, was capable of straightening it ,cutting it to length and bending it to U-shape, ready for insertion.
I believe that these machines are still used for large productions, especially for single sided boards, but a simple piece of wire has some disadvantages:
- it is difficult to handle (by hand): the "resistor body" type is larger, and is easier to pick-up and insert by hand
- it is too lightweight, so it moves up during board manipulation and wave-soldering process (see photos in a previous post: the jumper wires don't look very professional...
- for double-sided boards, it can short to top-side copper traces if the solder-resist is damaged.

This is the reason that, for low production runs, they use the "resistor-like" type (the one with the single black band). For large production runs, I have no recent experience: nobody makes large production anymore, here in Italy....

Regarding "wattage",  obviously it has no meaning: it is a simple way to indicate size (yes, they have quarter an half watt types).

Why are they used? There are multiple reasons:
- on single sided boards, as jumpers to replace a track that should be on component side.
Sometimes even in dual-side boards some reasons (difficult routing of tracks, track size, "straighter" way for signal, etc)  suggest to use a jumper.
- on both single and dual sided boards I've used (and seen other designers use) jumpers (made with wire or with "zero ohm") to leave the possibility of an afterthought, or to allow for different versions of the same boards, or whatever.
I've not a great experience with the SMD version, but I believe they are used for the same reasons.

Last point:  ohm must be written with lower case letters. Upper case must be used for the unit's symbol (in this case a Greek omega, that I cannot write here).
The same for volt, ampere, watt, meter, farad, henry, etc...
 
 

[gregariz]

I believe that these machines are still used for large productions, especially for single sided boards, but a simple piece of wire has some disadvantages:
- it is difficult to handle (by hand): the "resistor body" type is larger, and is easier to pick-up and insert by hand
- it is too lightweight, so it moves up during board manipulation and wave-soldering process (see photos in a previous post: the jumper wires don't look very professional...
- for double-sided boards, it can short to top-side copper traces if the solder-resist is damaged.

This is the reason that, for low production runs, they use the "resistor-like" type (the one with the single black band). For large production runs, I have no recent experience: nobody makes large production anymore, here in Italy....

I used the old fashioned shorting pins and plugs several years ago. They are still available at places like keystone. But most people design them out these days by simply using multiple layer boards. The other reason would be in high power stuff. I'm working on a high power amplifier at the moment where 0 ohms are just not going to cut it so I've opted for shorting plugs instead.

I almost always use 0 ohms on RF designs in order to debug a board during prototyping and usually keep them in during the manufacturing cycle (they cost almost nothing and will help in later debugging of any problems). The reason is that an RF design never comes up without a whole lot of bench work and you need to isolate it section by section until it all works together. Then put the 0's in (quite often I'll use a 1nF cap instead of a 0) and voila..

[ejeffrey]

One reason to use zero-ohm axial resistors over wire links is that they are insulated.  This would be important if you were using them on a hand etched board with no solder mask.  Even a commercial product with a nice mass produced PCB may have started out with a hand etched board.  It also helps prevent contact with adjacent components, if only by forcing you to space your wire links to accommodate the resistor body.

For mass production it helps that they come on reels with the same dimensions as a regular resistor.

For hand assembly of manufactured PCBs with solder mask, I don't see a real advantage -- as long as the board actually has the space allocated as it would for a regular resistor.

[metalphreak]

Most of the jumpers they use in single sided boards (the ones without any ceramic package) usually just come in a big bag, and are hand fitted.

http://www.goodluckbuy.com/3-10mm-length-u-shaped-silver-tone-jumper-wire-cable-for-breadboard-thick-10000-pcs-.html

I grabbed a bag of 8mm jumpers They're perfect for bridging the centre gap on breadboards (2 pin gap between each end)

[AntiProtonBoy]

Just for kicks, http://farm6.static.flickr.com/5302/5614765792_bac140e704_b.jpg Here's a picture of a board with quite a few 0 Ohm resistors.

It's witchcraft... all of it...