checkqert.blogg.se - Soldering iron for ona holes

Old solder should be removed and replaced with new solder whenever a component is reattached.

Solder needs to remain ductile in order to absorb the stresses of expansion and contraction caused by heating and cooling. Every time that solder is reheated, the molecular structure tends to become increasingly brittle. Reheating solder three or four times - even with the addition of flux - may affect the physical composition of the metals. If it becomes part of the new solder joint, it will have been heated at least three or even four times. That solder has already been heated twice.

If a component was previously soldered at the rework location, some of the original solder will remain attached to the pad.

If needed, reform component leads or replace the component if the leads do not meet the specification required.īefore inserting a component into a plated through hole for through-hole soldering or onto pads for surface mount soldering, it may be necessary to remove any excess solder.

If needed, tin component leads prior to soldering.

The temperature and time of baking are to be determined on an individual basis. The time between bake and soldering should not exceed five days, depending on the atmosphere's humidity levels.

If required, circuit boards should be baked in a suitable oven to remove any absorbed moisture.

Oxidation and contamination should be removed by methods that do not damage leads or parts and do not cause contamination or hinder solder wetting.

If needed, circuit boards should be cleaned prior to soldering and component removal operations.

If the tip is too large, it may extend beyond the edges of the component and contact another component or the surface of the circuit board. The smallest tip should be selected, providing that the tip fits over the entire component and contacts all the leads evenly. If the tip is too large, it may extend beyond the edges of the component and cause reflow to adjacent components or burn the surface of the circuit board. The smallest tip should be selected, providing that the proper airflow is delivered to the leads and solder joints.

If the tip extends too far beyond the edges of the joint, it could come in contact with another component or the surface of the circuit board. The outside diameter of the tip should not cover the pad completely or touch the circuit board base material or solder mask. The smallest tip should be selected, providing that the tip fits over the component lead and allows room for molten solder and air to pass through it. Larger tips with more surface area will transfer heat faster than smaller tips. The size and shape of the component removal tip will have an effect on the rate of heat transfer. Where possible, the width of the soldering iron tip should be slightly smaller than the width of the pad. While there is no exact rule about how the size of a soldering iron tip should compare to the size of the termination, if the tip extends too far beyond the edges of the joint, it could come in contact with another component or the surface of the board. Tip size is based on the size of the component.

The size and shape of the soldering iron tip will have an effect on the rate of heat transfer. Figure 3: Remove excess solder from surface mount pads using a vacuum desoldering tool.Ĭaution: Silicon based lubricants or hand creams should not be used on or near surfaces to be soldered.