How to test the life of metal dome?

We often receive this question from customer, what’s the life of this metal dome?
When we tell them answers, some customers will ask how do you test it? Hereby we will tell you.
But firstly, we should let you know, we don’t have a unified test method in the market, different manufacturer, different result.
1) Test probe: ofter use rubber probe & tungsten steel probe, diameter from 1.5mm to 3.0mm or more bigger.
2) Test force: We use two times of metal dome active force, but in Europe, they only use 1.1 times, so our method is more strict.
3) Test Frequency: 2-3 times per second (120 times -180 times per min).
Now are you clear?
Best Technology Co., Ltd is the leading manufacture of metal dome & dome array for more than ten year, please feel free to contact us for the more informations.

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!

Four-Leg Dome with Legs

As we know, there’re already four legs for our Four-leg series metal dome, and this is why it named four-leg dome, or cross metal dome. So what do you means “four-leg dome with legs”?

Let me firstly see the looking of a normal four-leg  (Cross) metal dome.

Normal four leg metal dome

We can see there’s no extra legs except these four legs which will be put on contact PAD of PCB, FPC, or membrane.

As we don’t recommend soldering metal domes on the board, so how do I adhere the dome, except normal “dome array“, “single key dome array“, or in the socket? Can I fix it on like triangle metal dome using two legs insert into the board hole? That’s the reason whey there’re extra legs for F series (cross) dome. You can see pictures.

four-leg dome with legs

four-leg dome with legs

Now is everything clear? There’re two extra leg, and you can insert the into the holes of board like triangle metal dome do. Currently on our Dia 11.4mm four-leg dome, these extra legs length is 1.2mm and width 0.9mm.

If you need more information about this special four-leg (Cross) dome with legs, contact BEST and we will give details to you. We can also make new tooling to make new diameter four-leg metal domes.

Circle Metal Dome with Leg

Previous we have discuss how to assemble triangle metal dome, some people told me they also want a circle dome with a leg. But for most of circle (round) series metal dome, there’s no leg.

So when assemble with a circle metal dome dome, you need to put it on a printed circuit board, or a flex circuit, by a adhesive tape,  or put it in a socket.

For 1st method, you can use our “standard single key dome array“; for 2nd way, just buy dome in bulk. it’s easy, but if you also want to fix circle dome in the socket, then you will hope this circle dome with a leg. Am I right? Hooo, dream comes true. Here are some pictures for them.

Circle dome with leg details 1

circle dome with leg details 2

Currently, there’re few circle domes has leg, because this kind of requirement can be replaced by triangle dome. So now only Diameter 5mm is available in the market now. Force 160gf, 180gf  are standard, 130gf and 200gf also no problem to be made.

If  you need other legged circle metal dome, we can set up new tooling to make the special dome. Contact BEST if you interest in this circle metal dome with leg.

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.