CN104972647A - Reflow soldering temperature control method of LED display screens - Google Patents
Reflow soldering temperature control method of LED display screens Download PDFInfo
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- CN104972647A CN104972647A CN201510374322.7A CN201510374322A CN104972647A CN 104972647 A CN104972647 A CN 104972647A CN 201510374322 A CN201510374322 A CN 201510374322A CN 104972647 A CN104972647 A CN 104972647A
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Abstract
The invention discloses a reflow soldering temperature control method of LED display screens. The reflow soldering temperature control method comprises following steps: LED lamps are subjected to roasting; temperature variation range and temperature variation speed of a preheating zone, a heating zone, a reflowing zone, and a cooling zone of reflow soldering are determined, and passing time of PCB boards through the preheating zone, the heating zone, the reflowing zone, and the cooling zone is determined; the direction of the PCB boards coated with solder paste is adjusted, and the PCB boards are delivered through the first temperature zone to the fourth temperature zone of a reflow soldering machine uniformly and successively; PCB boards with insufficient solder, missing solder, or continuous solder are subjected to repairing; and then the soldered PCB boards are delivered to a subsequent working procedure. According to the reflow soldering temperature control method, low temperature is adopted for reflow soldering as far as possible when reflow soldering peak temperature is capable of satisfying tin coating quality requirements, so that damage on parts caused by high temperature is avoided effectively.
Description
Technical field
The invention belongs to LED display and manufacture field, be specifically related to a kind of reflow soldering method of LED display.
Background technology
In recent years along with the lifting of LED wafer brightness and the fast development of encapsulation technology, SMD LED is more and more higher in the occupation rate in display screen field, fast-developing to outdoor display screen application by initial indoor display applications, the annual growth at double especially of its consumption.Although SMD LED increases severely in the use amount of display screen, but we also see that a lot of SMD LED display in the early stage and the later stage, constantly there is failpoint (blind point), even with some international top-brand product, can wild effect be there is too, form powerful contrast with the long-term stability of the direct insertion LED of tradition.
Cause display screen to break down and mainly contain some reason following:
1, display screen SMT technique imperfection, causes quality hidden danger, causes the later stage unstable, constantly occurs failpoint (blind point).In the SMT operation of display screen, the biggest threat that SMD LED bears be thermal stress under high temperature and moisture gasification time moment impact, especially show obvious especially for epoxy resin class wrapper SMD LED.
A. thermal stress
SMD LED is formed by the Material cladding that the polymorphic types such as support, wafer, die bond primer, connecting line (gold thread, alloy wire, palladium copper cash or aluminium wire) and epoxy resin, thermal coefficient of expansion are different.Polyphthalamide in its medium-height trestle (being called for short PPA) resin and the reliability effect of epoxy resin to LED maximum, the stress influence that is heated is remarkable especially.Epoxy resin can present different forms under normal temperature state and the condition of high temperature.Hard and crisp under normal temperature, then in rubber-like under high temperature.Temperature when transferring to the latter by the former is referred to as TG point (Glass Transtation Temperature), that is: glass transition temperature.When temperature is more than TG point, epoxy resin can present larger thermal coefficient of expansion, and numerical value is different at different temperatures for the thermal coefficient of expansion of epoxy resin, and the rising with temperature constantly increases, such as certain epoxy resin: 20 DEG C, be about 56.8 × 10-6m/cm/ DEG C, 160 DEG C, be about 65 × 10-6m/cm/ DEG C, and gold (Au) is 20 DEG C time, be about 14.2 × 10-6m/cm/ DEG C, and gold (Au) raises with temperature, thermal coefficient of expansion change is considerably less.In this case, when SMD LED is when bearing SMT high temperature, the stress mismatch of its inside can be more and more serious, when the limit that mismatch is born to sealing wire, LED inside just may there is sealing wire fracture and encapsulating structure impaired, cause occurring failpoint (becoming blind point).
B. moisture causes damage when high temperature reflux welds to support and product structure
All polyphthalamides absorb certain moisture, all can cause plasticization, and such as certain PPA resin is at 25 DEG C, and when relative humidity is 100%RH, after wettability is saturated, its vitrification point Tg point can significantly decline.After the glass transition temperature of PPA reduces, the high temperature of Reflow Soldering will cause PPA resin to produce deformation, PPA resin occurs that deformation produces displacement by causing the metal framework of PPA resin inside, the solder joint that will produce when shift length acquires a certain degree on metal framework departs from and elargol is peeled off, there is failpoint (blind point) or intermittent failpoint (just having started can be bright, can become blind a little after display screen lights a period of time) in SMD LED.
After exposing for a long time in atmosphere before SMD LED component SMT: hydrone can penetrate into high brightness in device package macromolecular material.Reflow Soldering starts: temperature <100 DEG C, and device surface increasing temperature, moisture content slowly gathers binder course.Rising along with temperature: temperature >>100 DEG C, moisture content gasifies, increased pressure, and peeling off appears in binder course, even " puffed rice ".This process, temperature is higher, and climbing speed is faster, impaired more serious.
Therefore, solder reflow process is to the stability of LED display, and quality all plays vital effect.
Summary of the invention
Technical problem to be solved by this invention is: the reflux temperature control method providing a kind of LED display, solves problem high due to the unreasonable LED display fault rate caused of reflow soldering process temperature parameter setting in prior art.
The present invention is for solving the problems of the technologies described above by the following technical solutions:
A kind of Reflow Soldering temperature-controlled process of LED display, first, LED is toasted, baking temperature is 40 ~ 60 degree, baking time is 8 ~ 24 hours, secondly, the variations in temperature of the preheating zone of setting Reflow Soldering, the thermal treatment zone, recirculating zone, cooling zone is interval, temperature changing speed and pcb board through the time of this warm area, concrete control method comprises the steps:
Step 1, preheating zone temperature are set as 80 ~ 150 degree, and the temperature of the thermal treatment zone is set as 150 ~ 180 degree, and the temperature of recirculating zone is set as 180 ~ 225 degree, and the temperature of cooling zone is set as 25 ~ 40 degree;
Step 2, control pcb board in 60 ~ 120 seconds at the uniform velocity through preheating zone;
Step 3, control pcb board in 60 ~ 120 seconds at the uniform velocity through the thermal treatment zone;
Step 4, control pcb board in 50 ~ 80 seconds at the uniform velocity through recirculating zone;
Step 5, control pcb board in 30 ~ 60 seconds at the uniform velocity through cooling zone;
Whether the pcb board after step 6, detection Reflow Soldering, have rosin joint, solder skip or connect tin phenomenon, if had, performs step 7, otherwise, perform step 8;
Step 7, to having rosin joint, solder skip or connecting after the pcb board of tin carries out maintenance process, perform step 8;
Step 8, the PCB welded is moved into next operation, then, repeated execution of steps 1 to step 8, completes the reflow soldering of all pcb boards.
The temperature of described preheating zone is 100 degree, and the PCB elapsed time is 90 seconds, and the heating-up temperature of the thermal treatment zone is 160 degree, the PCB elapsed time is 90 seconds, and the heating-up temperature of recirculating zone is 215 degree, and the PCB elapsed time is 60 seconds, the temperature of cooling zone is 25 degree, and the PCB elapsed time is 60 seconds.
The trivial temperature of described preheating is 80 degree, and the PCB elapsed time is 120 seconds, and the temperature of the thermal treatment zone is 180 degree, the PCB elapsed time is 60 seconds, and the heating-up temperature of recirculating zone is 225 degree, and the PCB elapsed time is 50 seconds, the temperature of cooling zone is 25 degree, and the PCB elapsed time is 60 seconds.
The baking temperature of described LED is 50 degree, and baking time is 12 hours.
The rate temperature change of the preheating zone of described Reflow Soldering, the thermal treatment zone, recirculating zone, cooling zone is all not more than 6 degree/second.
Compared with prior art, the present invention has following beneficial effect:
1, set reflow soldering peak temperature when on meeting when tin quality, use low temperature (being less than 245 DEG C) to carry out Reflow Soldering as far as possible, effectively reduce the damage of high temperature to device.
2, putting into baking box by opening the SMD LED after bag before welding, re-using after carrying out the drying of 60 DEG C/24 hours and preheating, with guarantee the temperature resistant capability of SMD LED do not decline and under reducing high temperature moisture to the damage of SMD LED.
Accompanying drawing explanation
Fig. 1 is Reflow Soldering temperature control curve figure of the present invention.
Detailed description of the invention
Below structure of the present invention and the course of work are described further.
As shown in Figure 1, a kind of Reflow Soldering temperature-controlled process of LED display, first, LED is toasted, baking temperature is 40 ~ 60 degree, and baking time is 8 ~ 24 hours, secondly, the variations in temperature of the setting preheating zone of Reflow Soldering, the thermal treatment zone, recirculating zone, cooling zone is interval, temperature changing speed and pcb board through the time of this warm area, concrete control method comprises the steps:
Step 1, preheating zone temperature are set as 100 ~ 150 degree, and the temperature of the thermal treatment zone is set as 150 ~ 180 degree, and the temperature of recirculating zone is set as 180 ~ 225 degree, and the temperature of cooling zone is set as 25 ~ 40 degree;
Step 2, control pcb board in 60 ~ 120 seconds at the uniform velocity through preheating zone;
Step 3, control pcb board in 60 ~ 120 seconds at the uniform velocity through the thermal treatment zone;
Step 4, control pcb board in 50 ~ 80 seconds at the uniform velocity through recirculating zone;
Step 5, control pcb board in 30 ~ 60 seconds at the uniform velocity through cooling zone;
Whether the pcb board after step 6, detection Reflow Soldering, have rosin joint, solder skip or connect tin phenomenon, if had, performs step 7, otherwise, perform step 8;
Step 7, to having rosin joint, solder skip or connecting after the pcb board of tin carries out maintenance process, perform step 8;
Step 8, the PCB welded is moved into next operation, then, repeated execution of steps 1 to step 8, completes the reflow soldering of all pcb boards.
The baking temperature of described LED is 50 degree, and baking time is 12 hours.
The rate temperature change of the preheating zone of described Reflow Soldering, the thermal treatment zone, recirculating zone, cooling zone is all not more than 6 degree/second.
Specific embodiment one,
A kind of Reflow Soldering temperature-controlled process of LED display, first, LED is toasted, baking temperature is 40 ~ 60 degree, baking time is 8 ~ 24 hours, secondly, the variations in temperature of the preheating zone of setting Reflow Soldering, the thermal treatment zone, recirculating zone, cooling zone is interval, temperature changing speed and pcb board through the time of this warm area, concrete control method comprises the steps:
The temperature of step 1, described preheating zone is 100 degree, and the heating-up temperature of the thermal treatment zone is 160 degree, and the heating-up temperature of recirculating zone is 215 degree, and the temperature of cooling zone is 25 degree;
Step 2, control pcb board in 90 seconds at the uniform velocity through preheating zone;
Step 3, control pcb board in 90 seconds at the uniform velocity through the thermal treatment zone;
Step 4, control pcb board in 60 seconds at the uniform velocity through recirculating zone;
Step 5, control pcb board in 60 seconds at the uniform velocity through cooling zone;
Whether the pcb board after step 6, detection Reflow Soldering, have rosin joint, solder skip or connect tin phenomenon, if had, performs step 7, otherwise, perform step 8
Step 7, to having rosin joint, solder skip or connecting after the pcb board of tin carries out maintenance process, perform step 8;
Step 8, the PCB welded is moved into next operation, then, repeated execution of steps 1 to step 8, completes the reflow soldering of all pcb boards.
Specific embodiment two,
A kind of Reflow Soldering temperature-controlled process of LED display, first, LED is toasted, baking temperature is 40 ~ 60 degree, baking time is 8 ~ 24 hours, secondly, the variations in temperature of the preheating zone of setting Reflow Soldering, the thermal treatment zone, recirculating zone, cooling zone is interval, temperature changing speed and pcb board through the time of this warm area, concrete control method comprises the steps:
The trivial temperature of step 1, described preheating is 80 degree, and the temperature of the thermal treatment zone is 180 degree, and the heating-up temperature of recirculating zone is 225 degree, and the temperature of cooling zone is 25 degree;
Step 2, control pcb board in 120 seconds at the uniform velocity through preheating zone;
Step 3, control pcb board in 60 seconds at the uniform velocity through the thermal treatment zone;
Step 4, control pcb board in 50 seconds at the uniform velocity through recirculating zone;
Step 5, control pcb board in 60 seconds at the uniform velocity through cooling zone;
Whether the pcb board after step 6, detection Reflow Soldering, have rosin joint, solder skip or connect tin phenomenon, if had, performs step 7, otherwise, perform step 8;
Step 7, to having rosin joint, solder skip or connecting after the pcb board of tin carries out maintenance process, perform step 8;
Step 8, the PCB welded is moved into next operation, then, repeated execution of steps 1 to step 8, completes the reflow soldering of all pcb boards.
Specific embodiment three,
A kind of Reflow Soldering temperature-controlled process of LED display, first, LED is toasted, baking temperature is 40 ~ 60 degree, baking time is 8 ~ 24 hours, secondly, the variations in temperature of the preheating zone of setting Reflow Soldering, the thermal treatment zone, recirculating zone, cooling zone is interval, temperature changing speed and pcb board through the time of this warm area, concrete control method comprises the steps:
Step 1, preheating zone temperature are set as 150 degree, and the temperature of the thermal treatment zone is set as 150 degree, and the temperature of recirculating zone is set as 180 degree, and the temperature of cooling zone is set as 40 degree;
Step 2, control pcb board in 60 seconds at the uniform velocity through preheating zone;
Step 3, control pcb board in 120 seconds at the uniform velocity through the thermal treatment zone;
Step 4, control pcb board in 80 seconds at the uniform velocity through recirculating zone;
Step 5, control pcb board in 30 seconds at the uniform velocity through cooling zone;
Whether the pcb board after step 6, detection Reflow Soldering, have rosin joint, solder skip or connect tin phenomenon, if had, performs step 7, otherwise, perform step 8;
Step 7, to having rosin joint, solder skip or connecting after the pcb board of tin carries out maintenance process, perform step 8;
Step 8, the PCB welded is moved into next operation, then, repeated execution of steps 1 to step 8, completes the reflow soldering of all pcb boards.
Claims (5)
1. the Reflow Soldering temperature-controlled process of a LED display, it is characterized in that: first, LED is toasted, baking temperature is 40 ~ 60 degree, baking time is 8 ~ 24 hours, secondly, the variations in temperature of the preheating zone of setting Reflow Soldering, the thermal treatment zone, recirculating zone, cooling zone is interval, temperature changing speed and pcb board through the time of this warm area, concrete control method comprises the steps:
Step 1, preheating zone temperature are set as 80 ~ 150 degree, and the temperature of the thermal treatment zone is set as 150 ~ 180 degree, and the temperature of recirculating zone is set as 180 ~ 225 degree, and the temperature of cooling zone is set as 25 ~ 40 degree;
Step 2, control pcb board in 60 ~ 120 seconds at the uniform velocity through preheating zone;
Step 3, control pcb board in 60 ~ 120 seconds at the uniform velocity through the thermal treatment zone;
Step 4, control pcb board in 50 ~ 80 seconds at the uniform velocity through recirculating zone;
Step 5, control pcb board in 30 ~ 60 seconds at the uniform velocity through cooling zone;
Whether the pcb board after step 6, detection Reflow Soldering, have rosin joint, solder skip or connect tin phenomenon, if had, performs step 7, otherwise, perform step 8;
Step 7, to having rosin joint, solder skip or connecting after the pcb board of tin carries out maintenance process, perform step 8;
Step 8, the PCB welded is moved into next operation, then, repeated execution of steps 1 to step 8, completes the reflow soldering of all pcb boards.
2. the Reflow Soldering temperature-controlled process of LED display according to claim 1, it is characterized in that: the temperature of described preheating zone is 100 degree, the PCB elapsed time is 90 seconds, the heating-up temperature of the thermal treatment zone is 160 degree, the PCB elapsed time is 90 seconds, and the heating-up temperature of recirculating zone is 215 degree, and the PCB elapsed time is 60 seconds, the temperature of cooling zone is 25 degree, and the PCB elapsed time is 60 seconds.
3. the Reflow Soldering temperature-controlled process of LED display according to claim 1, it is characterized in that: the trivial temperature of described preheating is 80 degree, the PCB elapsed time is 120 seconds, the temperature of the thermal treatment zone is 180 degree, the PCB elapsed time is 60 seconds, and the heating-up temperature of recirculating zone is 225 degree, and the PCB elapsed time is 50 seconds, the temperature of cooling zone is 25 degree, and the PCB elapsed time is 60 seconds.
4. the Reflow Soldering temperature-controlled process of LED display according to claim 1, is characterized in that: the baking temperature of described LED is 50 degree, and baking time is 12 hours.
5. the Reflow Soldering temperature-controlled process of LED display according to claim 1, is characterized in that: the rate temperature change of the preheating zone of described Reflow Soldering, the thermal treatment zone, recirculating zone, cooling zone is all not more than 6 degree/second.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109742213A (en) * | 2019-01-02 | 2019-05-10 | 东莞市科明光电有限公司 | A kind of built-in LED patch plug-in unit lamp packaging technology |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104325205A (en) * | 2014-10-24 | 2015-02-04 | 苏州佑瑞检测技术有限公司 | Reflow soldering method of SMD (Surface Mounted Device) components |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104325205A (en) * | 2014-10-24 | 2015-02-04 | 苏州佑瑞检测技术有限公司 | Reflow soldering method of SMD (Surface Mounted Device) components |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109742213A (en) * | 2019-01-02 | 2019-05-10 | 东莞市科明光电有限公司 | A kind of built-in LED patch plug-in unit lamp packaging technology |
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