SMT Assembly FAQs (Part 2)
1.Does the red dot means pin 1 in the placement previewer?
Generally, we do not call the red dot pin 1, but a marking only, which used to indicate the orientation of the components. As shown below, basically, there will be a dot on the components itself, and there will also a dot on the PCB(silkscreen), when they match, that means that the components are placed correctly.
2.What if the orientation for the component showing wrong in the placement preview?
The 0 degree that you defined for your design may be different from the one that we defined, but we both use the same rotation. So, sometimes you will find that there are some components in the wrong orientation. In this case, you can modify the rotation in your pick&place file and get it corrected. If you don’t know how to change the file, please just place your order, our engineers will review and fix the rotation and polarity of the components based on the silkscreen markings before assembly.
3.About the “0” degree for the package
There is only one simple rule: Zero orientation for PCB library should match the component orientation in the packaging(tape/reel).
In most data manuals, there are clear regulations and the way how components are placed in the package is marked. Very few small companies without the right to speak are subject to the packaging factory, and the problem of messy angles will appear.
The following are the examples of standard applications.
For example, you can set the direction with this soldering tool as below.
For diodes like SOD-123、LL-34、SMD LED ( 0603 LED、0805 LED ).
Photo of “0” degree placement of diode components in the parts library.
4.The reasons of different price for the component
For most of SMT components, it requires a minimum quantity to process SMT assembly, or extra parts to cover possible attritionduring assembly process, so there is a minimum order quantity required. When the quantity of the components you required does not reach the minimum quantity, it will charge the fixed fee as minimum Qty required. Please note that unused parts will not be sent because they are discarded directly in the production process.
5.When the components will be restocked?
Usually our purchasing department will have their own purchasing plan, they will evaluate the purchase time based on the remaining inventory. However, since the delivery date is unpredictable, we don't know the specific arrival time either, but you can check it on the website regularly. If you are in a hurry to place an order, it is recommended that you first check whether the component is in stock or not.
6.Why there is in stock on LCSC website but not in JLCPCB library?
The reason is that our components sources are from LCSC, and LCSC has two warehouses located in Jingsu and Shenzhen. So sometimes the components are shown available on LCSC website, but it shows 0 when you are placing order. This situation is caused by different warehouses sources, and we have no way to transfer them.
7.What components will we assemble?
Generally, we only assemble those components which you have confirmed when ordering. If you haven’t click the “confirm” button for the components, even if they occurs in the BOM file, we will not assemble them for you. Please kindly check and make sure you have not missed any components when placing the order.
8.About the +/- symbol in the DFM
Usually, "+" represents the positive electrode（Anode） and "-" for the negative electrode(Cathode). However, it seems that some countries are using the “A” and “K “values for electrode, which equal to “+” and”-” accordingly.
9.Why SMT order do not support Review Before Payment?
Usually when you place an SMT order, the system will occupy the components first, and other customers can no longer use the components you occupied. Due to various problems such as jet lag, once the order cannot be paid in time, the components will be occupied continuously, which will hold up the resources and other people will not be able to use them. So the SMT order need to be pay fist. We will think about other ways to fix the issue in the futures.
10.Why only 10 kinds of extend components can be used at one time?
Since the extend components are not commonly used as those basic component, and unlike basic library are fixed on the SMT production line, the extend components need to change the feeders manually every time, which will result in relatively large labor costs. At the same time, since your board is panelised on the big boards with other customers, if one customer uses too many components from extension library, it will affect the SMT assembly efficiency for all customers.
11. How do we judge the polarity for the components?
There are 2 situations:
1. Basically, we will judge them according your silk layer. If there is no silk layer or no any points for the us to judge how the componensts should be on your pcb, we cannot recognize the correct polarity. Then we will confirm with you via email. Due to the time difference and other uncontrolled issue, it will cause production delay. Therefore, we recommend you to add silkscreen layer to your PCB so that we can confirm them easier and faster to avoid production delay.
2.When there is mark point in the silkscreen layer, but it is inconsistent with your CPL file. In this case, we will make the placement according to the silkscreen layer by default. Thus please make sure your file is correct to avoid the misunderstanding.
For example, for the component C1, the “+” (Anode) is matched with the mark point in your silk layer by default, but in your CPL file it is reversed (as picture 2), then we change the polarity from the original part placement into a corrected part placement according (as picture 1) to the silkscreen layer in the filewithout asking.