Outline
This procedure covers the general guidelines for through hole component removal using a solder fountain system.There is basically only one style of the through-hole component. Whether there are a few leads or many, or whether the component is large or small, the component removal principles using this method are the same. Caution - Operator Safety: This process uses molten solder and exposes the untrained operator to serious hazards. A thorough review of the equipment manual and comprehensive training is mandatory. Daily maintenance is essential. Consult the equipment manual for more information. Caution - Component Sensitivity: This method may subject the component to extreme temperatures. Evaluate the component's tolerance to heat prior to using this method. Caution - Circuit Board Sensitivity: Circuit boards are made from a great variety of materials. When subjected to the high temperatures of the molten solder used in this method, they are susceptible to the following types of damage: 1. Layer delamination. 2. Copper delamination, separation of pads, barrels of inner layers. 3. Burns and solder mask chipping. 4. Warp. Each circuit board must be treated individually and scrutinized carefully for its reaction to heat. If a series of circuit boards are to be reworked, the first several should be fully protected until a reliable procedure is established.
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Images and Figures![]()
Through Hole Component
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Figure 1: Typical solder fountain system.
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Procedure
Solder Fountain SystemMost solder fountain systems have the same basic components. A solder pump and solder reservoir, various nozzle sizes, and controls for solder flow height. Solder from the reservoir is driven up through the nozzle by the pump. Nozzles are made of steel with welded seams and connections. It is important that the nozzle construction allows for the capture of the pump's inflow and for the runoff of the solder. This prevents the excess solder from splashing and maintains a usable solder level above the nozzle lip. Occasionally the opening in the solder fountain table needs to be restricted to prevent solder splash from contaminating the unworked part of the board. Do not close the opening too tight or you may impede the nozzle runoff. Above the solder fountain head, there is generally a light projected alignment mark that permits you to center the part to be removed over the nozzle. Solder Height Adjustment Solder height should be set at 1.50 mm - 3.00 mm (.060" - .120") above the lip of the nozzle. The ideal situation is to have the leads of a component just immersed and wetted without having the wave exert any upward pressure on the circuit board. The solder fountain table surface should be parallel to the nozzle surface. Components and leads on the bottom side of the circuit board may cause the PC board to be uneven, this condition must be compensated for. Insufficient immersion will prevent proper heat transfer and reflow. Excess pressure will cause the solder to surge up through holes and spill out onto the top side of the circuit board. Solder Temperature Adjustment Solder temperature adjustment varies depending on various factors. Normal setting 260 C (500 F.) During heavy use, solder temperature may cycle between 250 C - 270 C (480 F - 520 F.) The heaters should react quickly to normal drops in temperature. The heaters may overshoot the preset temperature when vigorous activity is suddenly halted. Operators must be alert to temperature fluctuations that exceed preset standards. Solder Fountain Time Adjustment This adjustment can be used to precisely control operations of a repetitive nature or in instances where you want to strictly control a circuit board's exposure to the solder fountain heat. The timer may also be set to maximum, and the on/off action of the wave is controlled by the motor on/off foot pedal or by lifting the board on and off the wave. Removal Tool There are a variety of removal tools to help extract the component once reflow has been achieved. The extractor tool should provide the operator a good grip but should not unduly damage the component during removal. PC Board Pre-heat Recommendations for pre-heat range from 1 to 4 hours at 65 C - 120 C ( 150 F - 250 F.) The requirements of temperature and time for pre-heat depend on the board construction, age, and exposure to the atmosphere. In general terms, the pre-heat will serve four purposes.
The area surrounding the component to be removed may need protection. If components or the circuit board surface are susceptible to damage or exposure to solder, they may be protected by using the following procedure:
Circuit boards returned from the field or where they have been exposed to moisture for some time.
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8.1.2 Component Removal, Through Hole Components, Solder Fountain Method
Procedure covers removal of through hole components on circuit board assemblies using a solder fountain system.