Drilling jig is one of them, but 90% of the jigs have been wave welded. This kind of jig is made of hard computer gongs, and some can move the twist drilling equipment or other drilling devices to the position of each hole accurately by moving the mold. A typical practice is to leave a hard collar on each hole of the drilling jig, so as to prevent the twist drill from cutting into the jig. The main point of the jig is that workers can borrow it quickly as long as it is the same product. However, if a small number of diversified products are produced, multiple jigs are needed, which will lead to high production cost.
In the process of smt chip processing, the mounting position of components is allowed to have certain deviation. The allowable deviation range requirements are as follows:
(1) Rectangular component: under the condition of correct PCB pad design, the width of the solder end in the width direction of the component is more than 3/4 on the pad, and after the solder end of the component overlaps with the pad in the length direction of the component, the protruding part of the pad is larger than 1/3 of the height of the solder end; When there is a rotation deviation, more than 3/4 of the width of the welding end of the component must be on the pad. Pay special attention when mounting: the solder ends of components must contact the solder paste pattern.
(2) Four-sided flat package device and ultra-small package device (QFP): 3/4 of the pin width should be on the pad, and small mounting deviation of X, Y and T (rotation angle) should be allowed. The toe of the pin is allowed to protrude from the pad a little, but the length of the pin must be 3/4 and the heel of the pin must also be on the pad.
(3) Small outline transistor (SOT): deviation of X, Y and T (rotation angle) is allowed, but the pins (including toe and heel) must all be on the pad.
(4) Small outline integrated circuit (SOIC): mounting deviation of X, Y and T (rotation angle) is allowed, but 3/4 of the device pin width (including toe and heel) must be on the pad.
