How to test the life of metal dome?

I often receive this question “ what’s the life of this metal dome? We require 1million times?” from customers, it’s very easy to tell you the answer, but I think you maybe want to know how to test and get the result.

Hereby I will tell you how to test the life of metal dome, but firstly, I should let you know, we don’t have a unified test method in the market. And right now, a lot of people use ASTM F15780-07: Contact closure cycling generally testing conditions. And the standard we used was more higher in most of areas.

1) Testing probe: Often use rubber probe & tungsten steel probe, probe size from 1.5 mm to 3.0 mm or more bigger, normally it’s 30% of diameter of metal dome.

metal dome test probe

metal dome test probe

2) Test force: We use two times active force of metal dome, but in USA and EU, most of customers only use 1.1 times, so our testing force is higher, so that the final life cycle result will be smaller than others, but that also means customer can get a more longer life cycles if using their own standard.

metal dome testing force

metal dome testing force

3) Test Frequency: 2-3 times per second (120 times -180 times per minutes), 72,000~10,800 times/hour.

metal dome life test speed and time data

metal dome life test speed and time data

Before testing, should pre-press the dome 5-10 times, then put this dome under the test probe, set the test condition and begin life testing, until metal dome broken.

We will record various parameters of metal dome after each 100,000 times testing. (normally take 10 hours to go through 100,000 times). These parameters will includes:

CP: Compression Peak Force;

CL: Compression Low Force;

RL: Release Low Force;

RP: Compression Peak Force

CC: Click Feeling:

(CC(%)=(CP-CL)/CP x 100%, it is normally between 35% and 60%.)

Travel (stroke):

Height:

metal dome force test report

metal dome force test report

For other parameters, please refer to another article: http://www.metal-domes.com/blog/2006/11/11/metal-dome-tech-and-parameter/

It will take 4-5 days to finish this metal dome life cycle testing, if your target was 1 million times. And for some metal domes, life cycles can be 2M or 3M times. And we are also developing new metal dome to achieve 5M and 10M times.

metal dome life test report

metal dome life test report

Also if your testing condition was different from us, the final result will be different. As mentioned above, most of customers in USA or EU will have longer life cycles than us, because different testing probe, force, or frequency. So maybe you can tell us what your testing parameters are so that we can simulate your metal dome life cycle testing condition to get a more closed result as yours.

Now are you clear how to test the life of metal dome? Below photo is the life testing machine. (metal dome life tester)

metal dome life tester

metal dome life tester

Best Technology Co., Ltd is the leading manufacturer of metal dome & dome array for more than ten years, please feel free to contact us, we will solve your questions. We are here, always with you.

What’s the tolerance for the stamping and cutting PET of dome array?

At present, have two methods to make dome array, one is cutting (by laser), another is stamping (by tooling), so some customers will ask what’s the tolerance of them, I made a comparison charts, please see it, then you can understand. Any more details want to know, please feel free to contact us.

tolerance: stamping vs cutting

the-tolerance-for-the-stamping-and-cutting-PET

If you are interested in metal dome & metal dome array, you can visit to products’s page for C (Circle) , F (4-Legs) , T (Triangle) , O (Oblong) Custom

If you would like to know  the packing method of metal dome & metal dome array, please visit to Metal Dome Packing for  In Bulk, In Tube, Tape & Reel, Peel & Place (Array).

 

How to Assemble Metal Dome Array on PCB

Some people will ask us how to assemble metal dome array on PCB, and today I’d like to share some basic information for that. It’s a very simple to assemble our metal dome array on PCB, and here are some basic steps:

 

1)    Clear the PCB, make sure there’s no dirt, dust, or any other contamination;

metal dome array and PCB

metal dome array and PCB

 

 

 

 

 

 

 

 

 

 

 

metal dome array before assembly

metal dome array before assembly

2)    Peel off metal dome array from the release paper;

Peel Off dome array from release paper

Peel Off dome array from release paper

3)    Find a good way for alignment of dome array and PCB, normally by location holes, outline edge, silkscreen/legend printed on PCB;

metal dome array location

metal dome array location 1

4)    Put dome array on PCB by handle, or machine (using a vacuum nozzle)

metal dome array location

metal dome array location 2

 

5)    Press surface of dome array to make sure it adhere on PCB firmly

press dome array on PCB

press dome array on PCB

6) Finished the assembly

dome array on PCB

dome array on PCB

 

Please to be noted that the self-adhesive on metal dome array has a small initial bonding force, so that you can peel off it from the PCB easily after assembly if you want to adjust location of dome array.

 

But this will also cause a potential problem: Customers will find dome array does not stick to PCB so firmly and then they will be a little worry.

 

In fact, there’s another special characteristics for that glue: the bonding force will become more and more stronger after about 24 hours, without any movement, pressure, etc. It means if after 24 hours, you cannot peel off dome array from the PCB, without damage the dome array, because the peel strength at that time will be extreme big comparing to initial value.

 

Let’s know if has more questions for metal dome array assembly on PCB.

New SMD Metal Dome Switch

Are you trying to find out a metal dome which can be soldered on circuit board? I think so, because the normal metal dome are not recommended to be soldered on the circuit because it will reduce or damage function of metal dome.

But now there’s a good news for you: We’ve release a new type of SMD dome switch today and you can choose suitable dome switch you like to assemble them on any of your board, without worrying anything!

SMD Dome Switch is a type of new metal dome package which designed to be soldered on PCB/FPC/MCPCB, or any other circuits, by directly SMT/SMD reflow soldering technology. The circuit board for soldering is on the bottom of each dome, and on top of metal dome, there’s a layer of yellowish Polyimide with a Plunger & Actuator in center area, to seal the dome and add the clicking feeling.

SMD dome switch from Best Tech

SMD dome switch from Best Tech

Please visit our website for more details: http://www.metal-domes.com/SMD-dome-switch.htm

Do you like that dome switch? If you have any idea or comments for that, please leave a message here, or write email to us. Any words on SMD dome switch will be appreciated.

 

Why Metal Dome Force Changed After Assembly on PCB

Recently one customer complain that the metal dome force changed so much after assembly on PCB.

The metal dome used was “X6T-350-0.8*3.0”(A Triangle dome,  Diameter 6mm, force 350gf, leg: 0.8*3.0mm). Before assembly, force is in normal force range 350gf, but after assembly on PCB, force change to about 500gf and then make whole dome key hard to press.

After saw customer’s PCB samples, we understand why this happened.

What method used was method A we recommend in “How to Assemble Triangle series metal domes on PCB (2)” (Please click to see more details for that article: http://www.metal-domes.com/blog/2010/07/02/assemble-triangle-metal-dome-on-pcb-2/)

Method is okay, but the problem was related with PCB design of customer. For Diameter 6mm triangle metal dome, the distance between two legs is 6.0mm, tolerance +/-0.2mm, so the tooling hole on PCB should be designed following that value.

6mm Triangle metal dome

But when we measure the PCB, the distance between holes on PCB is only5.35mm. You can see a picture bellowing.

PCB Hole Distance

Because hole distance on PCB is too narrow, so it’s difficult to insert leg of metal dome into the PCB. You can see when put metal dome on the PCB holes, it will not go into the holes, but remain above the PCB.

When you press metal dome and leg can be inserted into the hole, but only one leg is properly installed, another one was shifted. You can see the red arrow.

Wrong PCB Hole Distance

When press metal dome, people have to add extra force to bend the edge metal dome toward to center, to make the diameter from current6.0mmto5.35mm, so that end of metal dome leg will be on the same level of PCB. That extra force will be at least 150gf, so final metal dome force become 500gf (350gf+150gf). This is the reason why metal dome force altered so much between before and after assembly.

After realizing the problem, customer re-designs PCB and problem solved. Metal dome force keeps the same before and after assembly on PCB.

Just remember to have the same hole distance like metal dome diameter. If dome used is6mm, then distance6.0mm, for8mm, use8.0mmhole distance.

If you are not sure about that, please contact us before you design the PCB. We will be glad to provide service.

Metal Dome Activation Force Conversion

Thanks to the big Earth we live on, so we can see different culture around the world, so we can see different measure method on the same thing, so different results. When we discuss metal dome, people use various units, here are how to convert different unit of activation force of metal dome.

Ounces (OZ)     Grams Force (GF)      Newtons (N)

4.00                         114.00           1.11

6.00                       170.00             1.66

8.00                       227.00              2.22

10.00                     284.00             2.78

12.00                     340.00             3.33

14.00                     397.00            3.89

16.00                      454.00            4.44

18.00                       510.00           4.99

20.00                      567.00            5.54

You can also easy convert them by yourself.

1OZ=28.35 g

1GF  = 9.80665 Newton

In fact, OZ is the unit for weight, seemed no business relationship with activation force, but  you can easy treat them as the unit for force, if you’re know little physics.

And Gram force (GF), or KGF (Kilogram Force) has never become the unit of International System of Unit (SI), but it’s popular here in China and Europe.

In our company, the default unit for metal dome activation force we used is GF (Grams Force), but it’s no problem for customer to use other different unit to measure the force of metal dome.

Leave a message or write email to us if you’re interest or has comment for activation force of metal dome.

PCB PAD Finishing for Metal Dome

If it is the first time you try to use metal dome or metal dome array on circuit board (PCB or FPC), then probably you want to know what kind of surface finishing of circuit board should be used if metal dome will be assembled on.

Basically there’re two types of surface finishing can be chosen: Gold (immersion or plating) and HASL (Tin). In most of time, we suggest using Gold. Why?

As you know, function of metal dome or metal dome arrayis to act like a switch, to make circuit to be closed or opened. And low contact resistance will be helpful for smooth, stable currency. All of us know Gold bas much better performance than Tin on electric conductivity. This is why we recommend Gold.

Gold-plating-PAD-on_PCB

 

 

 

 

 

 

Whatever metal dome will be assembled on Rigid PCB, or flex circuit, gold is primary choice. Here are some pictures.

Gold-plating-PAD-on_FPC

 

 

 

 

 

 

 

But when you need lower price, does not need strict stable currency or don’t care too much on switch on/off time, and then you can choose HAL (Tin). For most of circuit board used in ESU pencil are of HAL (LF). Here are pictures.

HAL-finishing-PAD-on_PCB

 

 

 

 

HAL-finishing-PAD-on_PCB

I hope above is clear for everybody. If still have question, leave your comments or send an email, we will reply very soon.

Metal Dome in Tube

Regarding the Four-leg metal domes, for small-medium volume production,
if people want a high assembly speed, but don’t have Automated SMT machine, we recommend us our metal dome in tube, as well as Peel & Place dome. And here,  I’d like to say more words about metal dome in tube. Next article we will discuss another.

metal dome in tubemetal dome tube packing

To use metal dome in tube, you must have a dome placement pen, or auto-pick-gun. You insert the tube into that device, then move the device above the place where you want to place a metal dome, then push a button, a dome will come out, to fall on that position.

Using tube dome, you only need to push the button to place the metal dome, and don’t need to pick a dome by a tweezers, so it’ll make dome placing become a easy job. You can put about 1,000-2,000 pcs per hour. In fact, some expert guy can reach up to 3,000 pcs, 5,000 pcs or more.

Also if you can send back the empty tube to us, we will give you some discount, but in most case, oversea customers will not do that, because shipping fee is more expensive than tube itself. But I think if some days later, the cost of tube increased and shipping cost lower down, people will consider to re-use them, in a green way. Just make sure the tube is clear, fresh from any dirt, dust.

All right, leave comments if you like this, or have some comments, or better idea to improve the tube metal dome.

Tape & Reel Metal Dome – On Sales

After more than one year R&D, we are going to release our new Tape and Reel metal dome, a new packing method of metal dome which is suitable for automated SMT machine.

Each metal dome is sealed in a socket on a continued tape and packed on a reel, so it can be picked and place like normal components such as resistor, capitor, on SMT machine. Metal dome packed in this way named as “Tape & Reel Metal Dome” Also someone name it as “Pick & place metal dome”.

Tape & Reel metal dome

Please note even this metal dome is used in SMT machine, we don’t recommend to solder them like normal components.

Now we provide 8.4mm, 12.2mm  Four-leg metal dome in this packing. 5,000 pcs and 4,000 pcs each reel, respectively. We will give you some discount if you  order them in Sep and Oct. It’ll save a lot of your assembly time and money!

Please visit our website for more information about Tape and Reel metal dome!

Large Metal Dome

Recently we saw some people search for large metal dome and ask me whether we can make 500mmx500mm metal dome, or even bigger, such as 1,000mmx1,000mm.

The answers are No, we don’t make metal dome in such big dimension. For four-leg series metal dome, Max one is Diameter 20mm; you can see from below pictures, it’s small.

20mm metal dome

For Oblong series metal dome, we can make is 50.8×12.7mm.

If you compare 20mm dome with a coin (50 cent, RMB) and you will find it is very small.

20mm metal dome VS coin

I am wondering maybe some people still confused metal dome and steel dome. I hope above words will enhance their understanding and solve some potential mistake.

Anyway, if someone really big, large metal dome, less than 50x50mm, which we treat it as custom metal dome, just write your purpose and sketch,  we can discuss to see the possibility to develop that new model for you, to meet customers’ requirements of various metal domes are what we working for.