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1、SMD焊接作业1. Keep the circuit board clean. Isopropanol or wood alcohol is suitable for removing light oils and grease. PCBs should always be washed under warm water, then oven dried at 60 degrees Celsius for 10 to 15 minutes. Handle the PCB by the edge only and avoid touching copper with your bare hand
2、s.线路板保持干净,轻微的油渍可以使用酒精去除,冲洗PCB板务必要使用温水,然后在摄氏60度下烘干10到15分钟,过程中务必只能手触板边,绝对不能手摸铜箔,尤其是裸铜.2. Use the right soldering iron for the job. You dont need to purchase a temperature controlled iron, special SMT tip or SMT hot gas reflow station. These tools might be used in industry, but only to save time and in
3、crease reliability.使用正确的烙铁,一般SMD并不需要特殊的烙铁,温控,SMD专用烙铁头,或者是热气式的焊枪,这些一般常见于工业生产用,这些工具只是可以节省时间及增加焊点可靠性,但并非是非用不可的工具.一般烙铁就可以焊接SMD,重点在于烙铁头的选用All sorts of SMT soldering jobs can be done with the common Weller workstation. The important point is select the right tip (i.e.: have several tips on hand). As with
4、any soldering job, the general idea is to have the joint up to temperature and soldered in a few seconds. Think about how much of a heat sink the joint will be and choose the tip based on that. Use of larger tips should be limited to areas of large solid copper plane (i.e.: ground plane). For all jo
5、bs except very very small parts, I use a small tip as shown above. With practice, you will learn what tip suits you best.一般的烙铁就可以做SMD的焊接,重点不在烙铁,而是烙铁头,进行锡焊接的要点在于接点的温度及焊接的时间,因此首先要想到的是焊接点上的吸热,并且继而想到要选用什幺样的烙铁头,一般会选用大烙铁头无非是有很大的裸铜或者是接地面上的焊点,只要有够多的经验并且注意细节,你很快就可以自己选用合适的烙铁头.Use L.M.P (Low Melting Point Sold
6、er) if you are experimenting. LMP solder is very similar to 60/40 solder, except that it contains 2% Silver. This Silver loading has two effects. It lowers the melting point (a few degrees) and it reduces the rate at which component metalisation leeches into the solder itself.使用低融点锡,这种锡与60/40锡相同,只是另
7、外加有2%的银,增加银有二个作用,一是降低融点,另外一个作用是增加锡融解后的延展度.SMT resistors, capacitors, ferrite beads, etc. all make there electrical connections via metalised pads deposited on a substrate (Alumina, ceramic, ferrite, etc). The metal used is often Nickel or a related alloy. One problem with soldering the same joint se
8、veral times, is that each time the joint is heated, some of the Nickel leaves the component and joins the solder. The is called leeching. Leeching is only a problem when the solder joint of a metalised component is heated several times. Leeching occurs at a faster rate with standard 60/40 solder tha
9、n what it does with LMP solder. 不论是电阻电容或电感,这些SMD型式的零件,都是采用金属介质成为端点,使用的金属介质包含镍合金等,这些零件端点上的镍合金经过多次焊接后,镍会游离出来在焊点上,这称为LEECHING,一般使用60/40锡时很容易产生LEECHING,使用低熔点锡,可以降低零件焊点上的LEECHING效应.The downside of LMP solder is that it is about 3 times the price of 60/40 solder and harder to obtain, although sources of s
10、upply have been quoted at the back of this article. 使用低融点锡的问题点在于价格,这种锡的价格大约是标准60/40锡的3倍,同时也不很普遍.If a kit was being built, where the component values are known, then 60/40 solder will be fine. If component changes are often and likely, then LMP would be more advantages for a long term reliable solder
11、 connection. .假如制程中的零件是就定位的,而且也不会常因为更换零件而做焊点的融接,则可以使用60/40锡,假如焊点异动频繁,则以低熔点锡较佳.Some people use solder cream sold by various shops. The advantage of solder cream, is that it has more flux than regular solder. The solder cream is made up of very fine balls of solder mixed with a water based flux.有些人会使用
12、锡乳膏, 锡乳膏的优点就是它含有较多的助焊剂,通常锡乳膏是由很小的锡球与助焊剂混合而成.Unfortunately, solder cream was never intended to be used with a soldering iron. In fact, because the solder sits in a water based flux solution, the cream needs to be dried out (i.e. : the water has been driven off) before the solder can be melted. This c
13、an be done by moving the iron tip close to the joint for a few seconds prior to moving onto the joint.很可惜的是,锡乳膏通常不用于烙铁作业,事实上,锡乳膏是呈液态状,因此锡乳膏制程需要烘干作业,也就是要在小锡球溶解前必须烘干,这用在烙铁作业时,可以先将烙铁头靠近焊点几秒钟,先烘干锡乳膏,然后再将烙铁头碰触焊点.In experimentation quantities, solder cream is only available as 60/40 mix. In my opinion, th
14、e SMT experimenter would be better off to use LMP solder and extra flux (from a tube or a pen) rather than solder paste. It is a matter of personal preference. If you like using the paste, then go for it!一般而言,适合实验用的的锡乳膏只有60/40,但使用于实验桌上还是以低熔点锡乳膏较佳,同时还需外加助焊剂.Use solder flux where possible. One of the
15、biggest problems with soldering SMT parts is that the amount of flux within the solder core is not sufficient for the joint. Professional SMT manufacturers use solder cream and controlled temperature ovens. However, soldering iron temperatures are far less controlled and often the flux has evaporate
16、d before the joint has solidified, leading to dry joint which is often dull in complexion.可能的话,尽量使用助焊剂,焊接SMD零件的最大问题点之一,在于焊接点上的助焊剂量往往不足,专业SMD制程往往使用锡乳膏作业,并且使用温控回焊炉,采用烙铁的缺点,就是温度不容易掌控,而且往往在焊点尚未就绪前,助焊剂已发挥殆尽,这就容易造成焊点的假焊.Solder flux has other advantages. Because of its liquid nature, it increases the conduction of heat from the iron tip to the joint. It also increases the surface tension of the molten solder which helps
