Regarding the Micro-SIM card, in fact, from a technical point of view, there is no essential difference between the Micro-SIM card and the Mini-SIM card. The only difference lies in the surface area, and it is still a meaningless plastic surface area. So, Micro-SIM card is not regarded as a technological innovation, but more like an unconventional means. If it is not for Apple’s huge appeal in the industry, if it is not for the iconic iPad 3G (now an iPhone 4), I’m afraid Micro-SIM card will not become a hot topic for everyone now~~

Let's first see the difference between Micro-SIM card and standard Mini-SIM card:

 

From the picture above, we can see that there are almost no differences related to the core part. Of course, the actual metal contacts of the Micro-SIM card are a little smaller than that of the Mini-SIM card, but such differences are not at all Many friends worry about the applicability of the Mini-SIM card, worry that cutting the card will destroy the function of the Mini-SIM card, or worry that the Mini-SIM card can no longer be applied to the ordinary Mini-SIM card after cutting the card. SIM card slot, these concerns are unnecessary~~ Let’s take a look at this issue from a technical point of view~~

First correct one point of view~~ Now when people talk about Mini-SIM cards, they will habitually call them "small cards", and Mini-SIM cards as "big cards". In fact, this is incorrect. Yes, because from the perspective of the development of the SIM card, there is actually a larger card. This is the beginning of the birth of GSM digital mobile technology. This SIM card conforms to the ISO7816 standard for IC cards and is used for A kind of IC card on the early mobile phone, its size is similar to the credit card we use, yes, it is the size before the Mini-SIM is not removed, the picture above, if you don’t remove the Micro-SIM card or Mini-SIM card from Removed from the plastic film, it can be said to be a standard early SIM card. Only the size of this specification is the real "big card"

Due to the miniaturization of mobile phones, the original "big card" can no longer meet the needs of development, so the current Mini-SIM, which is commonly known as "small card", has emerged. However, the standards alliance has made this SIM card compatible with the original The big card design, therefore, is completely consistent with the big card in the definition of metal antennae, and even maintains the appearance of the big card. Therefore, if people use a big card phone, as long as the Mini-SIM card is not removed from the plastic package, It can be applied to early mobile phones. This compatibility policy has been retained until now, which is why Mini-SIM cards always have a huge plastic package~~

In other words, in a strict sense, if the Mini-SIM card is called "small card", then the Micro-SIM card should be called "micro card" for a long time~~

Okay, let’s talk about the Mini-SIM card cutting problem. Before that, let’s take a look at the physical structure and function definition of the Mini-SIM card:

The standard Mini-SIM card has a main card size of only 25mm×15mm. The main function is the copper metal contacts on the card surface and the logic circuit inside the card sealed with internal glue. The Mini-SIM card passes through the card surface. Copper metal contacts are used to connect the logic circuit in the card to the data exchange between the mobile phone. The Mini-SIM card chip has eight contacts. Usually, at least six contacts are required to connect to the mobile phone, as shown in the figure below:

 

You can compare your Mini-SIM card. Basically, except for the slightly different shape of the metal contacts, there will be no difference in the definition of contacts (unless it is a special card, such as South Korea). SIM card with 1G storage or RFID SIM card used by Sh1b0), that is to say, all Mini-SIM cards, including so-called Micro-SIM cards, conform to the functional division and definition of the above metal contacts. 

In addition to the metal contacts, I just said that the core function is the logic circuit in the card hidden under the metal contacts. This is a small logic circuit with a size of only about 3-5 square millimeters, which is sealed by glue. The method is hidden in the center position under the metal contact piece (that is, the position slightly above the center of the entire Mini-SIM card). Because this logic circuit is quite fragile, and if it is left exposed, it will easily lead to security such as information theft. Problem, so, the back will use plastic to make a thick plastic base to prevent the logic circuit from physical damage and ***. Therefore, it is difficult for us to see the true face of this logic circuit. This logic circuit is actually equivalent to a micro The processor, which generally contains 5 modules, each module corresponds to a function: microprocessor CPU (8 bits), program memory ROM (3--8kbit), working memory RAM (6--16kbit), data memory EEPROM (128-256kbit) and serial communication unit. After these 5 modules are glue-sealed on the copper metal contacts of the Mini-SIM card, they are basically the same as ordinary IC card packaging. 

The 32k card or 64k card we often say refers to the size of the data memory EEPROM (128-256kbit) in the card. According to the development history of the Mini-SIM card, the storage capacity is 3kB, 8kB, 16kB, 32kB, 64kB and even now 128k etc. At present, most of them are 64k and 128k (note that k is lowercase). We often see an STK menu in the mobile phone, indicating that this is an STK Mini-SIM card that supports STK services, and the STK card (SIM application Tool Kit) is a SIM card One is that it can provide value-added services for mobile phones, such as Monternet. The number of functions in this part, as well as the number of short messages and calls that the Mini-SIM card can store, depends on the size of the data memory EEPROM in the card~~ 

Well, through the above description, we summarize:The function of the Mini-SIM card depends on the completion of the internal logic circuit of the card and the integrity of the copper metal contacts responsible for the communication between the internal logic circuit and the mobile phone~! 

But in fact, let’s look at the difference between Mini-SIM card and Micro-SIM card:

 

The above is the International Organization for Standardization's definition of the size of various specifications of cards compared to SIM cards. The numbered ID-000 is what we call Mini-SIM card, and the numbered Mini-UICC is what we call now Comparing the size data of the two Micro-SIM cards, it is not difficult to find that, in addition to the extra plastic packages other than the metal contacts, in fact, there is almost no difference in the size of the metal contacts, and because Mini-SIM is defined At the beginning, redundant metal contact positions have been reserved. Therefore, actually cutting off some of the metal contacts has almost no functional impact on the entire Mini-SIM card (after all, the internal logic circuit still retains ~), everyone just think about the CPU can work only by relying on metal contacts, not to mention the metal contacts with such ample space? In fact, the original definition of such a large-area metal contact was just to ensure that the slight differences in the production of SIM card slots produced by various manufacturers would not cause abnormal Mimi-SIM connections~~ This is based on safety and applicability. Consider and make a margin at the technical level~ 

Therefore, we must be clear that the metal contact is not the functional essence of the Mini-SIM card, but an auxiliary connection contact. As long as the card does not affect the internal logic circuit, it will not have any substantial impact on the function~~~ It is particularly important to note that since the metal contacts of the Mini-SIM card are at the bottom, the left and right sides are defined as N/C (blank). Therefore, when there is a size conflict, as long as the top and center parts of the metal contact The symmetry of the entire SIM module (to prevent contact and misalignment with the SIM card slot), the bottom part of the metal contact can be reasonably "sacrificed". In this way, the Mini-SIM card must conform to the Micro-SIM The size of the card slot is simply a small Ks~~ 

In fact, as early as 2004, the first batch of applications that cut Mini-SIM cards into Micro-SIM cards were born in China. Yes, some brothers may have known about it, which is the so-called "cutting card." Type dual card", this is a way to cut the Mini-SIM card into the size of the Micro-SIM card today (actually, it is smaller than the Micro-SIM card), and then use the card paste to make two A Mini-SIM card can be squeezed into a 25mm×15mm Mini-SIM template at the same time. Then, through the coordination of the internal circuit of the card sticker, the mobile phone can simply switch between the two Mini-SIM cards through the STK menu. It avoids those business people who have two SIM cards, the trouble of constantly removing the battery and replacing the card, and it can also avoid the accidental loss of the SIM card and maintain the maximum compatibility on the physical circuit

 

There are many such products, and the names of manufacturers are countless. However, the technology is basically the same, but there may be a little difference in the optimization of STK program compatibility~~ 

The most important thing here is not to introduce dual cards, but the card-cutting technology applied here for the first time~~ 

Since its development in 2004, it can be said that when it comes to cutting card technology, there are probably few places in the world that are better than ours.

The Mini-SIM card processed in this way is even slightly smaller than the so-called Micro-SIM card. By the way, let’s take a look at the effect of the clip card used by the dual-card:

 

From the rough edges of the card in the picture above, it can be seen that the cutting process is not very good, and compared to the part cut off on the bottom of the Micro-SIM card, although this "work method" is really not flattering, I believe that after reading this picture , You should at least be confident and won't cut worse than the above, right? 

After cutting the card, insert the template of the dual card, it will become the size of an ordinary Mini-SIM card as shown in the figure below~ 

After processing, the thickness will be slightly increased compared to the real Mini-SIM card, but the increase may be less than 1 mm. For the Mini-SIM card slot of most old phones, it can still be inserted by squeezing it. , By the way, this is how I put two Mini-SIM cards in my dad’s mobile phone. Of course, my handwork is much better than the picture above~~~ 

Haha~~~~

However, few people are using dual-cards nowadays. The main reason is the thickness, because nowadays mobile phones are becoming thinner and thinner, and the space for a SIM card slot is getting smaller and smaller, and it is becoming more and more precise. Even a small increase of 0.5 mm will cause it to fail to be inserted, so this thing gradually "decays" and is replaced by later free-cut cards and copy cards.~ 

But in any case, for those who have doubts about the safety of Mini-SIM card cutting, you can rest assured that this technology has been developed in China since 2007 and has been verified by countless pioneers. Are you still worried that cutting the card will cause your card to become invalid? Unless your card cutting technology is so bad, you can actually cut the logic circuit located in the center of the SIM card. If so, I can only quote the words of Master Xing. The admiration for you is like a surging river~~~ ~ 

Since card cutting has such a long history in my celestial dynasty, I don’t have to bother with codewords about the skills of cutting cards. I can just use the tutorial of a certain manufacturer. If you find an advertisement about a manufacturer’s brand, please I just ignore it, I am too lazy to cover it~~ 

 

There is a part at the end of the tutorial, which is mainly about the installation of dual cartoons. I will not post this part. We mainly need the operation of cutting cards~~ 

In the card cutting operation, although we do not have the sticker mentioned in the first step (this is for the dual card), pay attention to the red letter prompt in the second step. This is a key. I have already explained the technical part just now. The logic control circuit of the Mini-SIM card is in the center. Therefore, confirming the center point of the Mini-SIM card is the key to the entire operation. The entire clip card must be symmetrical with this center point as the axis. As long as the center axis is confirmed, we will not You need the sticker mentioned in the first step to easily complete the card cutting operation~~ 

Of course, we can also make the cards in the tutorial by ourselves. The length and width of the Micro-SIM are 15mm×12mm (for details, please refer to the standardization organization card size data mentioned above), so as long as you make it on your computer Micro-SIM size card, and then print it out with a printer (transparent film is best), in fact, the effect is the same~~ 

The next part is very simple. First, we need to take the center of the metal contact piece as the core, and cut the metal part completely according to the size mentioned above, and then check the size of the Micro-SIM card slot. If the size is If there is a problem on the above and it does not meet its size, then we can continue to modify it, paying special attention to the symmetrical modification. In addition, the metal contacts on the bottom can be "sacrificed" a little bit more, for the reasons I have already said. , Because this part of the circuit definition is blank and has little effect on the function, and because the area of ​​a single defined metal contact is relatively large, a slight loss of symmetry will not have any effect~~ 

Well, so far, we have proved that cutting the Mini-SIM card into a Micro-SIM card is not a problem, and there is no big risk. Now the remaining question is how to change the Micro-SIM card back MIni-SIM card~~ 

Here I would like to compliment the imported card cutting device "Cut My Sim" mentioned earlier. It does have a good point, that is, it is equipped with a template that can restore the Micro-SIM card to the MIni-SIM card, as shown in the figure below. :

 

This makes "Cut My Sim" look perfect and useful. However, let’s take a step back and say that if we are careful when cutting the card, and use the art da0 instead of the cut da0 for operation, it will be based on the original Mini-SIM card. Take out the Micro-SIM card, so that you can have a Micro-SIM card and a Mini-SIM card template at the same time. The only thing to note is that the stress during the cutting of the art da0 may cause the incision to be upturned. If the da0 position is raised On the front side, there is a chance that a piece of metal contact piece and logic circuit will peel off from the plastic at the bottom, but if this happens, a drop of ordinary universal glue can solve it perfectly~~ 

Let’s take a step back and say, if we don’t use the art da0 and directly use the scissors da0 to operate, wouldn’t everyone expect that the original "big card" part of the Mini-SIM card should be plasticized and used to process it into a MIni-SIM card template? Even looking for a useless plastic discount card or VIP card, it can be easily processed into a MIni-SIM card template. Compared with the above operation, this is simpler and without risk. Finally, to ensure that the Micro- The SIM card can be fixed on the MIni-SIM card template made by yourself. Just find a thinner transparent sticker (3M original transparent sticker is very thin) and stick it together. Because it is a sticker, it is sticky It can be used repeatedly on the body~~ 

Besides, even for those who don’t like hands-on viewing, after reading my previous introduction to dual cartoons, there should be a glimmer of light in their heads. If the Micro-SIM card really starts to become necessary, Tianchao Manufacturers follow up to produce a small template, which is not a problem at all. Why bother to worry about it? (After P.S. was written, it was discovered that a similar product has already appeared on Taobao in Tianchao, called MicroSIM adapter, and the price is less than 10 yuan. It seems that Tianchao’s merchants have a good mind and response. The picture above:

 

Not to mention here, we still have a great copy card solution that can be used by the masters (unfortunately, the new number segment, such as the 186 card, can’t crack the key for the time being), so the Micro-SIM card of Jobs is for our citizens , Not a shit at all~~ 

Except for those copied cards, if the official channels are used to make up the card, there is only one valid SIM card for a number, and I will not explain the others~~