How to choose between PCB panelization and SMT
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At present, with the continuous increase of labor costs and processing costs, and the continuous upgrading of intelligent machinery and equipment, the PCBA SMT process pays more and more attention to quality and efficiency, and whether the circuit board panelization method is reasonable is crucial to the quality and efficiency of SMT. At the same time, the panelization method affects the material and processing costs of PCB, which will eventually be transmitted to the user's purchase price. Let's use a question-and-answer method to discuss how to ensure quality and improve efficiency by panelization while taking into account the purchase price of PCB. 1. Comparison of the pros and cons of circuit board panelization and non-panelization [table] [tr][td=148] Comparison [/td][td=345] Panelization [/td][td=307] No splicing of boards[/td][/tr] [tr][td=148] Advantages[/td][td=345]1. For large quantities of orders, the manufacturer's efficiency is relatively high and the delivery is fast 2. SMT can mount multiple boards at a time, which is more efficient than single board mounting and effectively reduces the mounting cost [/td][td=307]The appearance is smooth, and the outer arc and bevel can be completely made[/td][/tr] [tr][td=148] Disadvantages[/td][td=345]1. No matter whether V-CUT or stamp hole is used for appearance processing, there will be burrs after splitting the board, and the appearance is not smooth enough. 2. The arc and bevel on the corner of the panel cannot be completely in place. Some of them will remain on the single board after the panel is separated. 1. The manufacturer is inefficient, the production time is slightly longer, and the delivery is slightly slower. 2. SMT can only paste one single board at a time, and the patch efficiency is low. 2. What is the appropriate size of the panel? The panel size usually considers the following aspects: A. After panelization, the PCB manufacturer can produce * Usually, the panel size that PCB manufacturers can accept is between 50*50mm and 500*500mm. Each PCB manufacturer will limit the size range due to different equipment, production efficiency and cost. **The size of the panels that our company can make is divided into two types: 1. The range of V-CUT is from 80*80mm at the minimum to 500*500mm at the maximum; 2. The size range of the gong groove + stamp hole is from 50*50mm at the minimum to 500*650mm at the maximum. B. Before SMT is completed, the boards are firmly connected, without breaking or deformation *The size of the panels needs to be evaluated based on the thickness of the board and the shape of the single board. 1. Board thickness: Usually, large boards can be assembled for boards with a thickness of 1.2mm or more. The maximum size of 0.8-1.0mm boards is 200*300mm, and the maximum size of 0.4-0.6mm boards is 100*200mm. 2. Secondly, look at the size of the connection. If the length of the connection is greater than 1/2 of the single board size, you can only consider the board thickness and not whether the connection strength is sufficient. If the length of the connection is less than 1/2 of the single board size but greater than 1/5, the size of the panel should be reduced by at least 30%, and considering adding connection points according to actual conditions to avoid board breakage. If the connection is less than 1/5 of the single board size, it is necessary to add connection points. (The connection positions mentioned here need to be processed with V-CUT or stamp holes. If they do not need to be processed, the connection positions can be appropriately reduced, but the client needs to cut them by himself) C. Maximize SMT efficiency *Determine the maximum size that can be made, the width of the process edge, and the direction of the process edge, that is, the direction of the board, according to the SMT equipment. D. The material cost of the manufacturer is within the standard range, and the price of the circuit board will not be increased due to excessive material cost. 51)] * The size of the panel after splicing is inserted into the size of the large material of the board. The higher the board utilization rate, the lower the actual cost of the manufacturer. If the board utilization rate is too low, the manufacturer will require to increase the PCB price, otherwise the manufacturer may need to produce at a loss ** According to the actual situation of our company, the following panel sizes and board utilization rates are better: 75mm, 80mm, 95mm, 105mm, 120mm, 130mm, 145mm, 165mm, 195mm, 245mm, 290mm. It is difficult to achieve the standard size in the actual splicing process. An error of +/-5mm is allowed. The manufacturer can fine-tune the size of the processing edge of the production board according to the actual situation to ensure the utilization rate of the board. 3. Does the panel need to add a process edge, and how big should it be? Whether to add a process edge depends on whether the SMT machine is a crawler type or a fixture type. The fixture type does not require a process edge, and the crawler type clamping edge usually requires 2-5mm. If the distance between the patch parts in the board and the edge of the board is far enough and will not be within the crawler range, then there is no need to add a process edge. If the parts are within the crawler range, a process edge must be added, and the process edge is used as the clamping edge area. The width of the process edge usually requires 3-10mm depending on the characteristics of the machine, with 5mm being the most common. 4. In which cases is V-CUT required and in which cases is gong groove + connection position (stamp hole) required? A. V-CUT *The outer shape has straight edges, or the protruding position has straight edges *The outer shape edges do not have to be smooth *No parts protrude from the board and push into other adjacent boards *Board thickness is not less than 0.6mm B. Gong groove + connection position (stamp hole) *The shape is irregular, round or special-shaped*Board thickness is 0.4mm *The outer edges must be smooth, and any outer arc and bevel must be made completely according to the file *Some parts protrude from the board and may hit other adjacent boards. Increase the spacing to prevent them from hitting *The local line is close to the edge of the board, the distance is greater than 0.2mm and less than 0.4mm, and there is no space to move into the board. If V-CUT is used, it may hit the line The following figure is V-CUT The following picture is the gong groove + connection position (stamp hole) 5. In which direction should the process edge be added? Generally, the process edge is added to the longer side, and the board enters the SMT machine vertically. In this way, the hardness of the board is relatively high, and it will not bounce due to the light pressure of the machine probe during patching. However, the area of the process edge of the extended side is larger, which in disguise increases the average price of a single board. If the hardness of the board is sufficient, it can be added in the short direction, the process edge area is small, the average cost of a single board is reduced, and the board enters the SMT machine horizontally. 6. Is it necessary to add positioning holes and optical points on the process edge? SMT usually uses MARK points for alignment. If there are no MARK points in the board, 2-4 MARK points must be added diagonally on the process edge. The size of the MARK point is generally 1.0mm. When the copper is exposed and tinned, if there are MARK points in the board, the process edge can be added or not. When the board factory is producing, positioning is required for molding and testing. Adding special positioning holes on the process edge makes the appearance relatively standard and positioning is more convenient. Therefore, 3-4 positioning holes with a diameter of 2.0-4.0mm will be added on the process edge, with a diameter of 3mm being the most common and the best to use.
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