Microwave Tech - Key points of high-frequency board process flow

Key points of high-frequency board process flow

Key points of high-frequency board process flow: 1. Cutting

(1) Check whether the high-frequency plates such as the type of plate, copper foil thickness, cutting size, plate thickness, dielectric constant, etc. are correct according to the process requirements.

(2) When the same model is produced at the same time with different materials, it should be marked and consistent with the instruction sheet so that the subsequent processes can identify and produce until the FQC is separated;

2. Drilling

(1) Use new drill bits for drilling, but not reground drill bits;

(2) Drilling is carried out with reference to the drilling parameters of the high-frequency board in the drilling operation file;

(3) Special attention should be paid to the phenomenon of entanglement when drilling, which can be overcome by adjusting the level of dust collection, the force of the presser foot and the speed of retracting the knife;

(4) Thick aluminum sheets and high-density backing plates are used when drilling holes to prevent the occurrence of peaks.

(5) Surface burrs and burrs are generally not allowed to be polished (specially, 1500 mesh water abrasive paper can be used for manual fine grinding). Therefore, new drills must be used when drilling holes, and the drilling parameters must be paid attention to;

(6) The board material is soft and fragile, please use soft paper to isolate the sequence. At the same time, because the surface of the copper foil is treated with an anti-oxidation film, it is not easy to remove fingerprints, and it is not allowed to touch the board surface with bare hands.

(7) For ARLON boards AD255, AD350, Rogers R03003, R03010, R03203 and other special materials (high water absorption), after drilling, it needs to be baked at a high temperature of 150 degree Celsius ± 5 degree Celsius for 4 hours, and the water inside the board is dried. ;

3. Surface treatment (soaking high frequency pore finishing agent)

(1) The material of the board is soft and fragile. It must be fixed when it is put on the shelf, and it must be moved slowly during the rocking process, otherwise the board will be easily damaged;

(2)Multi-layer high-frequency boards and double-sided boards with slots larger than 2.0mm need to be etched first;

(3) High-frequency boards (except Rogers' hydrocarbon plates R04233, R04350, and RO4003) need to be immersed in high-frequency pore-forming agent treatment. If the multi-layer board needs to be treated with high-frequency pore-forming agent, it is necessary to bake the board after etched 130 Degree 2 hours;

(4) When immersing the high-frequency pore refining agent, ensure that the surface of the board is dry and enter the tank; (that is, the process is: pitting + baking sheet + high-frequency pore refining agent + sinking copper)

4. Porosification Due to the poor wettability of high-frequency sheet PTFE material, surface treatment is required to complete the chemical copper deposition at one time. The process can be as follows:

(1) When copper sinking, the concentration of the medicine can be appropriately increased and the copper sinking time can be prolonged;

(2) In principle, double-hanging splints are used for thickening copper plating and pattern electroplating, but it should be determined according to the drilling position, the size and position of the auxiliary edge other than the peripheral hole should be observed when mounting, splinting, and inserting. Damage the substrate,

(3) The material of the high-frequency plate is soft and fragile. When the plate thickness is thin, it can not be turned on and swayed to avoid intermittent short circuit burning of the cathode and anode. The operator should observe the ammeter indication at any time.

(4) When producing high-frequency boards, the sinking copper wire potion tank must be ultrasonically closed before production.

Five, graphics production transfer

(1) When self-checking the first board, the operator should use a 100-fold lens to strictly check the microstrip line width and line spacing;

(2) In order to prevent the deformation of the microstrip line, the exposure parameters and development parameters must be determined according to the first plate;

(3) When there are many coupling lines on the high-frequency board, use hinge yin and yang shots or parallel exposure machine alignment to enhance alignment accuracy;

Six, graphic plating

(1) The spray tin plate is determined according to the customer's requirements. If there is no requirement, the copper plating is 60 minutes, the DK is 1.6-1.8 A/dm 2, the copper layer thickness is controlled at 20-25um, the tin plating is 10-15 minutes, and the DK is all in 1.5 A/dm 2;

(2) The nickel/gold plate is determined according to customer requirements. If there is no requirement, copper plating for 20 minutes, DK is 1.6-1.8 A/dm 2; nickel plating for 12-15 minutes (as thin as possible), DK is 1.8-2.0 A/dm 2.

Seven, remove the film

(1) Removal film must be thoroughly clean;

(2) The tin plate must control the removal film concentration (5-10%NaOH), the temperature is 50-65 degree Celsius, and the plates should not overlap when removing the film to prevent the tin from dissociating and the film removal is not complete, resulting in lines and teeth after etching. glitch.

Eight, two diamonds

(1) Due to the high frequency plates (except Rogers hydrocarbon plates R04233, R04350, RO4003) plates are easy to deform, the second drill is carried out before the etching after the film is removed, to prevent serious deformation after etching and cause the second drill to deviate.

Nine, etching

(1) Etch the first board and self-check the microstrip line width and line spacing, and meet the requirements for mass production. If it does not meet the requirements, report to the relevant personnel for adjustment and confirmation;

(2) After the sprayed tin/immersion gold plate is etched and passed the sampling inspection, do not return the tin and send it to the inspection first.

(3) For high-frequency plates (except Rogers hydrocarbon plates R04233, R04350, RO4003), the plates cannot be ground after etching.

10. Etching inspection

(1) Strictly check the microstrip line width and spacing with a 100-fold lens (2) The residual copper in the microstrip line and the vicinity of 2.54mm must be removed;

(3) The residual copper layer on the edge of the microstrip line must not be removed with a blade, but can be removed by etching again to avoid scrapping

(4) The microstrip line is required to be flat and smooth, without burrs, dog teeth, or pits;

(5) For high-frequency plates (except Rogers hydrocarbon plates R04233, R04350, RO4003), the plates cannot be ground after etching.

(6) AD255 and AD350 and RO3003\R03010\R03203 in the PTFE material, after the etching inspection, the 2-3mm surrounding process edge should be electro-milled to expose the base material. After milling, the baking sheet 150 is plated for 2 hours to prevent the resistance from soldering. The substrate blisters after baking or spraying tin.

11. Pressing

(1) In addition to meeting the requirements of PP thickness, the adjacent layers of PP are evenly arranged, and the latitude and longitude of the adjacent layers are kept consistent, and the influence of the thickness of the interlayer dielectric on the characteristic impedance needs to be considered;

(2) In the PTFE material, AD255 and AD350 and RO3003\R03010\R03203 and other plate inner blind hole boards need to mill off the copper on the surrounding process edges to expose the base material before laminating, and insert the frame at 150 degree Celsius ±5 after electric milling Bake the board at degree Celsius for 2 hours to prevent the substrate from foaming during lamination. After browning, it is necessary to insert the rack with a 120 degree Celsius baking sheet for 1 hour and then laminate it.

(3) For high-frequency boards (except Rogers hydrocarbon boards R04233, R04350, RO4003) boards, the boards cannot be ground before and after browning.

12. Solder mask

(1) Pretreatment of gold-plated plate: clean and dry with a gold plate washing machine - low temperature (75±5 degree Celsius) pre-baked for 30 minutes and then naturally cool to room temperature (more than half an hour) - apply solder mask (one solder mask is enough)

(2) PTFE high frequency (non-hydrocarbon sheet R04233, R04350, RO4003) spray tin / immersion gold / immersion tin plate pre-treatment:

A: Solder mask should be printed after tinning and de-tinning. Direct acid drying before soldering, and the board should not be ground in the first soldering;

B: The tin plating does not remove the tin and does not print the solder mask, just grind and dry the board directly before the solder mask;

C: If the tin plating does not return the tin and the solder mask is to be printed, it is sufficient to clean and dry before the solder mask (can not be ground);

D: Under certain conditions of A and C above, you need to see whether the second solder mask is indicated in the flow sheet. If it is indicated, it can be washed and dried with high pressure water before the first solder mask. (Secondary solder mask is required For the first solder mask, rework film production is required.) Before the second solder mask, item C does not need to be pickled and polished, and item A needs to be acid polished;

E: Before solder mask printing, pre-baked at low temperature (75±5 degree Celsius) for 30 minutes and then cooled to room temperature (more than half an hour) before printing solder mask;

(3) PTFE high-frequency board (without hydrocarbon board R04233, R04350, RO4003), tin spraying/immersion gold board requires two solder masks, and tin sink board requires three solder masks.

(4) Add 50ml of boiling oil and water to the high-frequency board for only one solder mask. When the second solder mask is required, the first boiling oil and water are 120ml, and the second and third boiling oil and water are both 50ml;

(5) After applying the solder mask, let it stand for more than 30 minutes, and then pre-bake, and set the time according to the thickness, thickness, size, and size of the board to ensure that the solder mask is cross-linked with the board;

(6) Bare copper plate: the first time after pre-baking, the rework film for solder mask is exposed to the position (the substrate needs to be covered with solder mask);

(7) Before developing and after exposure, be sure to stand for 15 minutes before developing;

Thirteen, post-baked

A: After the gold-plated plate is sent silkscreen, it is baked (segmental baking) 75°C pre-baked for 30 minutes, then 120°C for 30 minutes, 155°C for 60 minutes (segmental baking is done in the same oven), when baking the plate Fix the board;

B: Tin plate: pre-baked at 75 degree Celsius for 30 minutes, then bake at 155 degree Celsius for 30 minutes to cool down - grind the board - print the second solder mask - QC inspection - post-baked (75°C for 30 minutes, 120° for 30 minutes, 155°C for 60 minutes) .

14. Spray tin / Immersion gold

A. TP-2 sheet material can not be sprayed with tin process, only manual 36W constant temperature electric soldering iron can be assembled;

B. The first board of spraying tin is to check whether the solder mask is falling off or blistering; whether the tin surface is flat, whether the hole wall is blasted; whether the substrate and copper layer are delamination or blistering, and whether the etched characters fall off.

C. When spraying tin, bake the board at 155±5 degree Celsius for 30min and spray the tin while it is hot to prevent blasting.

D. The tin-sprayed board without solder mask needs to be baked at 155±5 degree Celsius for 4 hours before tin-spraying;

15. Characters

(1) Curing conditions: 155±5 degree Celsius baking sheet 30min

(2) PTFE high-frequency board(R04233, R04350, RO4003 without hydrocarbon) is not for solder mask, but it is necessary to print characters on the substrate and not be polished to prevent the characters from falling off.

(3) When solder mask is required and the characters are printed on the base material, it is necessary to communicate with the customer. The characters cannot be printed because the plate has been ground during the second solder mask. In principle, customers are recommended to etch copper characters (copper characters should be appropriately Large to prevent falling off) or the character design is printed on the solder mask.

16. Shape processing

(1) V-CUT molding is not recommended for PTFE materials;

(2) The parameters of the gong board are carried out according to the requirements of the high-frequency board of the electric milling operation document.

(3) Corn milling cutters cannot be used for electric milling of PTFE materials. Special milling cutters are required. The compaction enhances the dust collection effect. When dropping the cutters, pay attention to the material entangled with the cutters and cause the cutter to break; if there are still fibers on the edge of the board, use the blade to remove;

17. Finished product inspection

18. Packaging

(1) The unqualified boards shall be sealed and stored separately for related routine tests. If the customer emphasizes that unqualified semi-finished products, finished boards and incoming materials are returned to the customer, they shall be packaged separately and clearly marked and delivered to the finished product warehouse;

(2) The boards that need to be delivered remotely are packed with foam boards to isolate the surroundings.